Pseudomonas Isolated from Spoiled Meat, Water, and Soil GORAN MOLIN and ANDERS TERNSTROM” Swedish Meat Research Institute, S-244 00 Kavlinge, Sweden

INTERNATIONALJOURNAL OF SYSTEMATICBACTERIOLOGY, Apr. 1986, p. 257-274 Vol. 36, No. 2 0020-7713/86/020257-18$02.OO/O Copyright 0 1986, International Union of Microbiological Societies

Phenotypically Based Taxonomy of Psychrotrophic Pseudomonas Isolated from Spoiled Meat, Water, and Soil GORAN MOLIN AND ANDERS TERNSTROM” Swedish Meat Research Institute, S-244 00 Kavlinge, Sweden

The phenetic taxonomy of 305 strains of Pseudomonas and related organisms was numerically studied by using 215 features, including 156 assimilation tests. A total of 200 field strains were isolated from spoiling meat, and 50 strains were isolated from freshwater or soil. In addition, 55 reference strains (including 23 type strains and 4 clinical strains) were obtained. The strains clustered into 25 clusters at the 75% level when the Jaccard similarity coefficient was used. The 10 clusters that were considered significant were assigned to the Pseudomonas fragi complex (131 strains), Pseudomonas lundensis (40 strains), Pseudomonasfluorescens biovar 1 (27 strains), P.fluorescens biovar 2 (5 strains), P.fluorescens biovar 3 (6 strains), P.fluorescens biovar 4 (16 strains), Pseudomonas aureofaciens-Pseudomonas chlororaphis (3 strains), Pseudomonas aeruginosa (4 strains), Pseudomonas glathei (2 strains), and Pseudomonas mephitica (2 strains). The P. fragi complex was further divided into subclusters; the major subcluster (comprising 93 strains, including the type strain) was regarded as P. fragi sensu stricto. P. fluorescens and allied bacteria closely matched the descriptions given by Stanier et al. (J. Gen. Microbiol. 43:159-271, 1966). The characteristics for the 10 significant clusters are given. Also given are criteria which differentiate the P. fragi subclusters. The phylogenetic relationships among the meat-associated taxa were calculated, P.fluorescens biovars 2 and 3 were clearly separated from the remaining taxa. Biovar 4 is the most conservative, while biovar 3 has evolved at the highest rate.

The spoilage of refrigerated meat by psychrotrophic strains and an extended battery of assimilation tests were pseudomonads results in tremendous financial losses, yet used was initiated. The major aims of this study were to very little is known about the nature and taxonomic position taxonomically clarify the phenetic relationships among P. of the spoilage organisms. Until the mid-1960s the lack of an fragi, cluster 2 of Molin and Ternstrom (20), and P. adequate classification system for pseudomonads prevented Jluorescens and to clarify the relationships between these real progress, and early investigations of the spoilage orga- groups and their external taxonomic surroundings. In addi- nisms merely added new inadequately circumscribed species tion, this study provided answers to the following two to the already vast number of almost nondescript Pseudomo- questions: (i) which taxa are dominant at a certain defined nas nomenspecies. stage of meat spoilage, and (ii) is the assimilation pattern of In 1966 Stanier et al. provided a framework for the a Pseudomonas strain reproducible when a different tech- taxonomy of Pseudomonas. The phenetic study of these nique and scoring system are used? Our results also pro- authors became the basis for a number of phenotypic and vided evidence for the phylogenetic relationships among the genotypic studies (4, 25, 27, 28, 31). However, the existence taxa. of nonfluorescent, psychrotrophic Pseudomonas strains re- sembling members of the Pseudomonas Jluorescens- MATERIALS AND METHODS Pseudomonas putida complex has been neglected. On the Isolation of meat strains. A total of 200 meat samples other hand, the occurrence of such strains in food sources (average weight, 0.5 kg) were obtained from the cutting lines has been reported frequently (5, 12, 30). Some of these of seven slaughterhouses in Sweden. The meat samples were strains have been assigned to the species Pseudomonas individually wrapped in gas-permeable polyethylene film and fragi, although quite frequently this has been done on aerobically stored at 4°C. Total aerobic plate counts were dubious grounds. The epithet of P.fragi (‘ ‘Bacteriumfragi”) determined on tryptone-glucose-yeast extract agar (Oxoid was originally used by Eichholz (9), and the organism was Ltd., London, England) (incubated at 25°C for 3 days) later considered (17) to be identical to “Pseudomonas throughout storage by using the cork borer method for fragariae” (13). In 1961 a type strain (strain ATCC 4973) was sampling (10). When the bacterial level on the meat surface proposed for the species (19). However, no adequate cir- was in the range of lo6 to 10’ CFU/cm2, one isolate was cumscription of the species was published. In 1982, two randomly picked from each tryptone-glucose-yeast extract papers concerning the phenotypic relationships among agar plate. Only one isolate was taken from each meat sample. pseudomonads isolated from meat were published (20, 29). The beef isolates were designated strains 301 through 400, Both of these studies showed that the major taxon, repre- and the pork isolates were designated strains 401 through 500. senting more than one-half of the meat strains, should be Isolation of environmental strains. Samples of fresh surface designated P. fragi because of the inclusion of the type strain water and soil were collected from 44 sites, representing an in the cluster. The second largest cluster of Molin and area of about 60,000 km2, in southern Sweden. In addition, Ternstrom (20) (cluster 2) was left unassigned, but it was three samples of tap water, two samples of adhesive bacte- suggested that this phenon might represent a new species. rial growth on stones that were fully submerged in streams However, questions concerning the homogeneity and re- (strains 529 and 548), and a sample of adhesive bacterial lationships of the two clusters still remained. Therefore, a growth on a glass surface subjected to running chlorinated new numerical, phenotypic analysis in which a new set of tap water for 1 week (strain 550) were collected. The soil samples were immediately plated onto tryptone-glucose- * Corresponding author. yeast extract agar, whereas the water samples were stored at

257 258 MOLIN AND TERNSTROM INT. J. SYST.BACTERIOL.

4°C for 10 days prior to plating. Only one isolate was taken TABLE 1. Designations and sources of strains, assimilation vigor from each sample. The selection of colonies were biased by values, and distances from the HMO and the type strain in the random picking among those colonies having diameters of P. frugi complex (cluster 1) more than 1 mm. Strains 501 through 525 and 549 were soil Distance (%) isolates, and strains 526 through 548 and 550 were water Sub- Source andlor name 2::i:!:i from: Strain cluster as receiveda isolates. The strains and sources of isolation are listed in (%) HMO Tables 1 through 4. 569T Type and reference strains. A total of 54 named reference 301 A Beef, Kavlinge 42 9 19 cultures, including 25 type strains, were used in this study. 304 A Beef, Kavlinge 43 9 16 The reference strains for the biovars of P. jluorescens were 336 A Beef, Kris tianstad 42 5 17 chosen from the strains used in a previous numerical study 429 A Pork, Kristianstad 43 7 18 (20). In addition, four clinical isolates of gram-negative, 418 A Pork, Kristianstad 44 6 15 aerobic, rod-shaped bacteria of unknown identity were ob- 399 A Beef, Kalmar 41 6 16 tained. 430 A Pork, Kristianstad 42 7 19 Three strains, “Pseudomonas bathycetes” ATCC 23597, 432 A Pork, Kristianstad 42 8 18 A Pseudomonas carboxydohydrogena DSM 1083T (T = type 334 Beef, Kris tianstad 40 7 15 Pseudomonas nautica 50418T, 350 A Beef, Savsjo 38 7 13 strain), and DSM did not 373 A Beef, Savsjo 41 7 19 grow or grew only sparsely under the experimental condi- 420 A Pork, Kristianstad 42 4 16 tions used, and the data for these strains were omitted from 473 A Pork, Varberg 43 4 16 the computations. 383 A Beef, Savsjo 40 4 16 The strains having a culture collection number were 306 A Beef, Kavlinge 42 7 14 obtained from the culture collection, except strain 573T (= 485 A Pork, Kalmar 40 9 17 CCM 3503*), which was isolated previously by Molin and 308 A Beef, Kavlinge 43 7 14 Ternstrom (20). The sources of the other reference strains 345 A Beef, Savsjo 41 8 18 are given in the footnotes to Tables through 4. 465 A Pork, Varberg 40 7 17 1 A The type and reference strains were designated strains 551 307 Beef, Kavlinge 39 11 16 437 A Pork, Tomelilla 39 11 18 through 605. The strains and culture collections from which 309 A Beef, Kavlinge 42 6 13 they were received are listed in Tables 1 through 4. 310 A Beef, Kavlinge 41 7 15 Phenotypic characterization. In all, 244 tests were per- 320 A Beef, Kavlinge 41 7 15 formed; 215 of these tests were used for the numerical 312 A Beef, Kavlinge 42 9 14 analysis. Unless indicated otherwise, the tests were per- 314 A Beef, Kavlinge 42 8 13 formed at 25°C and read after 4 days. 317 A Beef, Kavlinge 42 7 15 Cultural characteristics and growth tests. Motility was 3 19 A Beef, Kavlinge 41 9 15 examined by phase-contrast microscopy following growth in 406 A Pork fat, Kavlinge 40 7 15 nutrient broth (Oxoid) for 20 h. Apparently nonmotile strains 483 A Pork, Varberg 40 6 14 499 A Pork, Kalmar 40 7 15 were examined further after prolonged incubation, after 489 A Pork, Kalmar 42 8 18 growth at 15”C, and after growth on nutrient agar (Oxoid). 498 A Pork, Kalmar 40 7 15 Strains showing no motility were checked six times before 327 A Beef, Kris tian stad 37 9 12 being regarded as nonmotile. Spreading growth on 331 A Beef, Kristianstad 37 9 12 cytophaga agar (1) was examined after 10 days. Growth at 333 A Beef, Kristianstad 37 9 12 different temperatures and in the presence of different so- 419 A Pork, Kristianstad 41 6 14 dium chloride concentrations was examined on nutrient agar 339 A Beef, Kristianstad 39 12 21 following 5 days of incubation, except for growth at 4”C, 375 A Beef, Savsjo 40 6 18 which was read after 14 days. Other tests for cultural 389 A Beef, Kalmar 38 6 14 393 A Beef, Kalmar 39 9 11 characteristics and growth (see Table 5) were performed as 342 A Beef, Savsjo 38 9 21 previously described (20). 400 A Beef, Kalmar 41 13 16 Biochemical and degradative tests. Hydrolysis of esculin 586 A P. frugi MT72 43 9 14 was determined as described by Edwards and Ewing (8). (beef)“ Amino acid decarboxylases were tested by the method of 571 A P. frugi MT182 42 9 17 M6ller (22). Production of phosphatases was recorded on (POW medium containing 5.0 g of peptone per liter, 5.0 g of Lab 3 18 A Beef, Kavlinge 42 13 11 Lemco (Oxoid) per liter, 5.0 g of NaCl per liter, and 15.0 g of 384 A Beef, Savsjo 42 12 13 agar per liter. After sterilization, 0.1 g of sterile filtered 422 A Pork, Kristianstad 42 11 10 427 A phenolphtalein disulfate per liter was added. Following Pork, Kris tianstad 41 13 11 428 A Pork, Kristianstad 42 14 10 incubation, the plates were inverted, and 1 drop of concen- 402 A Pork, Kavlinge 40 9 11 trated ammonia was placed onto each lid. The development 445 A Pork, Tomelilla 40 8 12 of pink colonies was scored as a positive result. Production 47 1 A Pork, Varberg 42 8 11 of polysaccharides from sucrose was examined in a nitrogen- 412 A Pork, Kavlinge 42 11 10 deficient medium containing 3.0 g of NaCl per liter, 0.5 g of 434 A Pork, Kri stian stad 40 12 11 yeast extract per liter, 3.0 g of Na2HP04per liter, 2.3 g of 446 A Pork, Tomelilla 42 8 7 KH2P04 per liter, 50.0 g of sucrose per liter, and 15.0 g of 408 A Pork fat, Kavlinge 40 8 14 agar per liter (pH 6.8). The development of big slimy 459 A Pork, Varberg 38 12 13 colonies, or colonies with a rubberlike texture was scored as 410 A Pork, Kavlinge 41 12 13 484 A Pork fat, Kalmar a positive result. Most other tests (see Table 5) were 39 17 14 423 A Pork, Kristianstad 42 11 14 performed as previously described (20); we used minor modifications for three tests. Gelatin hydrolysis was re- Continued on following puge VOL. 36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMUNAS 259

TABLE 1-Continued TABLE 1-Continued Distance (%) Distance (%) Sub- Source and/or name from: Sub- Source andor name :::::- from:” ‘ Strain cluster as ra--:.da cluster as receiveda or (%) HMO Strain 569‘ 481 A Pork, Varberg 43 12 13 495 B2 Pork fat, Kalmar 40 20 25 488 A Pork, Varberg 44 12 11 456 B3 Pork, Varberg 40 18 25 493 A Pork fat, Kalmar 42 14 13 458 B3 Pork, Varberg 40 15 22 43 1 A Pork, Kristianstad 42 12 13 482 B3 Pork, Varberg 41 14 21 460 A Pork, Varberg 44 14 13 463 B3 Pork, Varberg 40 17 24 569T A P.frugi ATCC 43 12 479 B3 Pork fat, Varberg 40 17 24 4973T 374 Beef, Savsjo 38 22 25 461 A Pork, Varberg 40 12 19 382 Beef, Kristianstad 38 22 28 462 A Pork, Varberg 40 10 18 540 River water 44 19 26 470 A Pork, Varberg 43 11 15 454 Pork, Varberg 37 22 31 344 A Beef, Savsjo 37 11 22 416 Pork, Kavlinge 36 31 32 405 A Pork, Kavlinge 38 8 20 ~-~ A a All samples were from Sweden. 496 Pork, Kalmar 37 10 21 The distances were calculated by using the S, coefficient. 492 A Pork fat, Kalmar 40 12 19 See reference 20. 397 A Beef, Kalmar 36 12 20 Obtained from Statens Seruminstitut, Copenhagen, Denmark. 486 A Pork, Kalmar 35 16 21 396 A Beef, Kalmar 38 11 18 corded after 14 days, and production of nitrogen from 490 A Pork, Kalmar 37 9 19 nitrate, as indicated by gas bubbles and rupture of the agar, 390 A Beef, Kalmar 49 16 18 was tested in tubes. Degradation of egg yolk was scored as 491 A Pork fat, Kalmar 44 11 18 positive only if opaque precipitation (an egg yolk reaction) 403 A Pork, Kavlinge 37 15 17 appeared around the patch; thus, zones of clearing were 407 A Pork, Kavlinge 37 15 17 disregarded. 417 A Pork, Kavlinge 38 16 18 Production of acid from carbohydrates. A modified Hugh- 450 A Pork, Varberg 37 16 17 477 A Pork, Varberg 37 16 15 Leifson medium containing 2.0 g of peptone per liter, 5.0 g of 411 A Pork, Kavlinge 42 17 16 NaCl per liter, 0.3 g of K2HP04per liter, 15.0 g of agar per 570 A P. frugi MT64 41 15 15 liter, and 0.06 g of bromocresol purple per liter (pH 7.1) was (Pork)= used to determine the production of acid from carbohy- 42 1 A Pork, Kristianstad 46 10 16 drates. This basal medium was supplemented with a sterile 603 A P.frugi AB469 41 16 20 filtered carbohydrate solution to give a final concentration of (flower pot 1% (wthol) prior to pouring onto plates. All shades of water)d positive reactions, ranging from yellow colonies to wide 604 A P. frugi PR367 40 17 23 (clinical yellow zones in the surrounding agar, were scored as posi- isolate)d tive. 353 A Beef, Savsjo 38 13 20 Assimilation of sole carbon sources. To determine assimi- 365 A Beef, Savsjo 36 19 22 lation of sole carbon sources, the basal medium of Palleroni 452 A Pork, Varberg 35 19 25 and Doudoroff (26) was used; it was Supplemented with 1.0% 303 B1 Beef, Kavlinge 41 17 25 (wthol) purified agar (Oxoid) as a solidifier. Most carbon 305 B1 Beef, Kavlinge 41 17 25 compounds, which were sterilized by various methods (20), 361 B1 Beef, Kristianstad 42 18 26 were added to concentrations of 0.1 (wt/vol) or (vol/vol); the 380 B1 Beef, Kristianstad 41 19 27 exceptions were DL-amino acids (0.2%), menthol and 311 B1 Beef, Kavlinge 41 19 22 taurocholate (0.05%), and deoxycholate, glycerate, 1- 355 B1 Beef, Savsjo 41 17 24 404 B1 Pork, Kavlinge 42 19 25 hydroxynaphthalene, and phenol (0.025%). The growth from 386 B1 Beef, Kalmar 40 15 24 1-day cultures on nutrient agar was mixed with a 0.9% NaCl 388 B1 Beef fat, Kalmar 40 15 24 solution to obtain a concentration of roughly lo9 cells per ml. 448 B1 Pork, Savsjo 40 14 23 Samples (2 pl) of bacterial suspension were then dispensed 476 B1 Pork, Savsjo 39 17 26 onto the various assimilation media by using a syringe fitted 455 B1 Pork, Savsjo 39 16 25 with a repeating dispenser unit and disposable tips (Hamilton 494 B1 Pork, Kalmar 40 15 24 Ltd., Bonaduz, Switzerland). To avoid growth interference, 316 B1 Beef, Kavlinge 40 17 24 the number of inoculations per plate was limited to seven. 348 B1 Beef, Savsjo 38 22 29 The plates were read after 7 days of incubation against a 414 B1 Pork, Kavlinge 40 20 28 315 B1 Beef, Kavlinge 39 22 29 black background, thereby scoring only “good growth” as 381 B1 Beef, Savsjo 40 18 25 positive. The cultures which produced doubtful results were 370 B1 Beef, Kristianstad 38 23 28 replated. The development of big mutant colonies was 377 B1 Beef, Savsjo 40 19 26 scored as a positive result. 349 B2 Beef, Savsjo 42 21 26 Seven tests were omitted because of low reproducibility or 409 B2 Pork, Kavlinge 43 19 24 dubious results or both, These tests were production of 413 B2 Pork, Kavlinge 44 19 24 lipase for tributyrin and assimilation of caprate, caprylate, 487 B2 Pork, Kalmar 44 19 24 1,3-dihydroxy-2-propanone,esculin, glutarate, and sperm- 398 B2 Beef, Kalmar 42 16 23 ine. 394 B2 Beef, Kalmar 43 18 25 Phenetic analysis. 497 €2 Pork, Kalmar 44 20 25 Based on a matrix containing 305 strains and 215 tests, a simple matching coefficient (SSM)for each Continued pair of strains was obtained as follows: SSM = (a + b)/(a + 260 MOLIN AND TERNSTROM INT. J. SYST.BACTERIOL.

TABLE 2. Sources of strains, assimilation vigor values and percentage of utilization of the various carbon sources) was distances from the HMO and type strain in P. fundensis (cluster 5) also calculated for each strain (31). The distances between the centroid of significant taxa were calculated as described Strain Source and/or name Assimilation Distance (%) from: by Champion et al. (4). as receivedn vigor (%) HMO Strain 573T Phylogenetic analysis. The phylogenetic relationships for 313 Beef, Kavlinge 29 21 23 the different clusters containing meat isolates were esti- 321 Beef, Kristianstad 29 10 21 mated. The HMO for each cluster was calculated on the 330 Beef, Kristianstad 29 8 18 basis of assimilation tests, excluding all tests giving the same 328 Beef, Kristianstad 30 6 18 results for all of the clusters involved, any problems with 338 Beef, Kristianstad 30 3 15 19 scoring, or with a high incidence of mutant colonies. In 332 Beef, Kristianstad 29 7 addition, the ability to produce a fluorescent pigment was 359 Beef, Savsjo 27 11 20 322 Beef, Kristianstad 29 13 22 included in the calculation. Altogether, 48 characters defined 325 Beef, Kristianstad 29 14 20 each HMO. Based on the HMOs, the most parsimonious 323 Beef, Kristianstad 30 14 20 tree (Wagner criterion) was calculated by using the Penny 329 Beef, Kristianstad 31 12 19 algorithm (branch and bound) as described by Hendy and 335 Beef, Kristianstad 29 15 22 Penny (15). The calculations were performed by using the 357 Beef, Savsjo 27 15 20 PHYLIP-Phylogeny Inference Package (version 2.6) con- 326 Beef, Kristianstad 30 8 20 structed by J. Felsenstein (University of Seattle, Seattle, 337 Beef, Kristianstad 32 7 16 Wash.). In order to get the tree rooted, the HMO of 478 Pork, Varberg 30 10 16 Pseudumunas mephitica 468 Pork, Varberg 31 13 17 was included in the analysis as an 366 Beef, Savsjo 29 10 17 outgroup. The reasons for choosing this organism as an 442 Pork, Tomelilla 32 12 14 outgroup were that, compared with the meat clusters, it was 376 Beef, Savsjo 30 11 15 the phenetically most distant psychrotrophic Pseudomunus 469 Pork, Varberg 31 11 15 sp. used in this study. 340 Beef, Savsjo 31 8 20 Test reproducibility. A total of 15 pseudomonad strains 441 Pork, Tomelilla 33 11 17 (strains 560, 562T, 564T through 567, 569T through 574, 586, 372 Beef, Savsjo 33 8 17 589T and 590) were tested previously by Molin and 358 Beef, Savsjo 30 8 18 Ternstrom (20). Correlations among the results of 102 assim- 444 Pork, Tomelilla 31 8 17 In the 426 Pork, Kristianstad 32 7 13 ilation tests used in both studies were calculated. 360 Beef, Savsjo 32 4 13 previous study the method used was somewhat different, 385 Beef, Savsjo 33 7 8 and scoring was done after 4 days of incubation by using an 424 Pork, Kristianstad 33 11 14 inoculated basal medium control plate without growth sub- 425 Pork, Kristianstad 33 9 13 strate as a reference. 433 Pork, Kristianstad 33 11 14 387 Beef, Kalmar 33 12 13 573T P. fundensis 32 12 RESULTS MT13gT (= Test reproducibility. The overall level of similarity of CCM 3503T) (beef)' assimilation test results between the present numerical study 574 P. fundensis MT65 31 12 13 and our previous study (20) was 89.6%. When we discounted (pork)" the results obtained with a few very slowly assimilated 438 Pork, Tomelilla 31 16 16 compounds (caproate, L-lysine, D-mannose, and trehalose), 439 Pork, Tomelilla 32 15 18 which were strongly affected by the longer incubation period 500 Pork, Kristianstad 29 14 18 used in the present study, the value was increased to 95.6%. 443 Pork, Tomelilla 30 17 21 Dendrogram structure. Dendrograms generated by using 436 Pork, Tomelilla 29 20 15 the SJcoefficient and the simple matching coefficient exhib- All samples were from Sweden. ited very similar structures, with fusion of 25 almost identi- The distances were calculated by using the SJcoefficient. cal clusters at similarity levels of 75% (Fig. 1 and 2) and 88%, See reference 20. respectively. Below, only similarities and distances based on the SJcoefficient are presented. Clusters 1through 5, containing 182 strains, merged into a b + c - nc), where a was the number of positive matches, b supercluster at the 65% similarity level. This supercluster was the number of negative matches, c was the number of was made up almost exclusively of meat strains. A second nonmatches, and nc was the number of noncomparable supercluster containing 84 usually fluorescent strains was matches. In addition, Jaccard coefficients (SJ)were calcu- formed at the 63% level. These strains, which belonged to lated as follows: SJ= u/(a + c - nc) (negative matches were clusters 6 through 18, were derived from meat, as well as ignored). Fusions were made by using the group average from environmental sources. The superclusters were joined method (unweighted pair group method, using arithmetic at the 59% level, and the merged aggregate was fairly well averages). Dendrograms were plotted by using both simple separated from the remaining 39 strains, which were joined matching and SJ similarity coefficients; only the latter are at levels of 50% or below. presented below. The software used was Clustan 2 (Release Cluster 1, the P. frugi complex. Cluster 1 comprised 131 2.1., University of St. Andrews, Fife, Scotland, 1982). strains, and all but 4 were of meat origin. These strains were Hypothetical mean organisms (HMOs) (18) were con- moderately vigorous and were capable of assimilating about structed for significant taxa, and the distances (DJ)between 40% of the carbon compounds tested, including D-arabinose, strains and various HMOs and type strains were calculated creatine, and bile acids (Table 5). Assimilation of these as follows: DJ = lOO(1 - SJ).The vigors for the assimilation compounds, together with the inability of cluster 1 strains to tests used in the numerical analyses (n = 156; i.e., the assimilate malonate and most other dicarboxylic acids, could VOL. 36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 261

TABLE 3. Sources, vigor values, and distances from the HMOs and type strain in the fluorescent supercluster (clusters 6 through 18) Assimilation Distance (%)from HMO of cluster:' Distance (%) from Strain Cluster Source and/or name as receiveda vigor(%) 10 8 6 12 11 Strain 5WT 324 6 Beef, Kristianstad 63 34 30 (141 35 42 38 364 6 Beef, Savsjo 58 34 28 34 39 37 566 6 P. fluorescens biovar 3 strain 56 34 29 36 36 ATCC 17400 594T 6 P. taetrolens CCM 1982T 53 32 31 34 34 457 6 Pork, Varberg 53 28 26 27 33 33 475 6 Pork, Varberg 49 29 27 32 29 354 7 Beef, Savsjo 64 36 26-- '29 40 40 35 363 7 Beef, Savsjo 58 34 25 36 32 32 504 8 Clay 57 32 26 33 30 31 54 1 8 Pond water 50 28 24 30 21 30 542 8 Lake water 54 27 24 28 21 30 544 8 River water 54 29 23 29 23 30 565 8 P.fluorescens biovar 2 strain 55 34 16 28 32 31 31 DSM 50108 l!! 528 Brook water 59 27 27 28 31 37 27 511 Clay 65 31 26 31 30 36 30 529 Adhesive growth 63 42 35 28 40 44 42 548 Adhesive growth 58 42 27 36 42 40 42 543 Lake water 47 45 26 29 40 38 41 576 Clinical isolatec 45 41 29 31 36 35 38 589T 9 P. putida biovar 1 strain DSM 50202T 49 41 32 37 30 39 39 590 9 P. putida biovar 2 strain 56 41 25 32 35 38 39 DSM 50222 - 341 10 Beef, Savsjo 43 9 32 29 22 23 22 466 10 Pork fat, Varberg 43 11 33 30 25 24 23 343 10 Beef, Savsjo 42 8 31 29 23 22 21 356 10 Beef, Savsjo 42 12 34 31 26 25 22 367 10 Beef, Savsjo 45 14 30 32 22 26 23 453 10 Pork, Varberg 47 14 27 30 19 22 20 440 10 Pork, Tomelilla 46 8 30 30 22 25 16 464 10 Pork, Varberg 46 10 30 32 23 26 18 45 1 10 Pork, Varberg 47 10 27 30 20 22 18 472 10 Pork fat, Varberg 41 12 33 30 23 23 19 480 10 Pork, Varberg 42 15 34 32 25 25 19 346 10 Beef, Savsjo 49 7 26 32 24 23 17 347 10 Beef, Savsjo 48 10 27 34 27 24 16 369 10 Beef, Savsjo 48 12 28 36 28 25 18 379 10 Beef fat, Savsjo 49 9 29 34 27 26 17 371 10 Beef, Savsjo 49 11 28 31 27 26 19 415 10 Pork, Kavlinge 48 12 30 34 29 28 18 546 10 Tap water 49 11 26 32 26 23 15 352 10 Beef, Savsjo 46 13 32 36 27 29 21 522 10 Sand 46 12 31 35 27 27 14 378 10 Beef, Savsjo 44 10 29 32 24 22 13 561 10 P. fluorescens P1 (milk)d 44 13 27 33 18 17 14 564* 10 P. fluorescens biovar 1 strain 47 15 30 34 27 24 ATCC 13525T 474 10 Pork, Varberg 38 27 31 37 31 26 30 593T 10 P. synxantha ATCC 9890T 43 13 24 29 20 18 20 467 10 Pork, Varberg 55 16 24 23 31 30 21 536 10 River water 55 -17 27 28 27 30 21 368 11 Beef, Savsjo 38 19 28 33 28 26 435 11 Pork, Tomelilla 38 23 31 34 27 13 28 507 11 Sand 42 28 24 40 30 29 518 11 Humus soil 46 25 22 39 31 27 519 11 Humus soil 42 24 22 38 30 27 517 11 Sand 42 34 32 44 36 34 501 11 Sand 40 23 23 35 23 24 503 11 Clay 41 28 27 39 26 26 513 11 Clay 40 30 25 37 26 26 5 10 11 Clay 43 26 25 34 25 27 5 14 11 Clay 45 26 23 34 25 26 512 11 Clay 42 26 25 37 25 25 567 11 P.fluorescens biovar 4 strain 40 32 22 37 26 13 29 DSM 50415 502 11 Boggy soil 42 28 28 34 26 15 30 Continued on following page 262 MOLIN AND TERNSTROM INT. J. SYST. BACTERIOL.

TABLE 3-Continued Assimilation Distance (%)from HMO of cluster:b Distance (%) from Strain Cluster Source andor name as received' vigor(%) 10 8 6 12 11 Strain 564' 508 11 Clay 42 28 28 37 28 31 525 I1 Peaty soil 38 31 34 42 27 559T 12 P. aureofaciens ATCC 13985T 42 24 30 33 20 25 560 12 P. aureofaciens DSM 50082 43 25 29 32 23 27 562T 12 P. chlororaphis DSM 50083T 46 26 26 25 21 28 515 13 Clay 42 26 24 34 29 16 30 53 1 13 River water 43 35 23 33 35 23 35 532 14 River water 45 23 26 31 32 26 25 535 14 Pond water 46 26 19 32 35 22 28 545 15 Tap water 46 27 36 23 28 29 29 568 15 P.fluorexens ATCC 948 38 24 35 28 29 23 26 505 16 Peaty soil 46 35 27 37 34 18 33 523 16 Clay 46 26 24 36 35 17 29 524 16 Clay 50 30 30 39 33 27 31 509 Clay 36 36 34 40 35 20 38 549 Gravel 37 35 33 36 27 25 32 533 Brook water 50 32 36 33 33 32 31 506 17 Loamy soil 44 34 32 38 33 25 36 530 17 Brook water 47 37 32 39 35 22 33 534 Pond water 52 33 30 39 34 26 37 520 18 Gravel 56 39 33 42 42 36 36 521 18 Sand 50 33 32 44 41 30 34

(I All samples were from Sweden. Clusters 10, 8, 6, and 11 correspond to biovars 1, 2, 3, and 4 of P.Jluorescens,respectively; cluster 12 corresponds to P. uureofuciens-P. chlororuphis. The distances were calculated by using the SJcoefficient. Isolated by G. Kronvall, Hospital of Lund, Lund, Sweden. Isolated by S. E. Birkeland, Mejeriinstituttet, As-NLH, Norway. serve as a basis for differentiation between the P. fragi stragglers, nonfluorescent reference strains 572, 601, and complex and the various biovars of P.JIqorescens. 605, which were all previously assigned to P.fragi (Table 4), Most of the strains belonging to the P.fragi complex could were located at distances of 21, 28, and 23%, respectively, be divided into four significant subclusters (Fig. 1). from P.fragi 569T. Thus, at least two of these strains would Subcluster A comprised 93 strains and included the type have joined the cluster within a 75% level if the type strain strain of P.fragi, strain 569 (= ATCC 4973). This subcluster had been at the center of the cluster. The remainder of the was fairly homogeneous, with most of the strains within a DJ adjoining strains were all fluorescent and belonged to two- of 15% from the HMO and all strains within a DJof 25% from member clusters 2 and 3 (Table 4). The position of these the type strain. As deduced from Fig. 1 and Table I, many strains in the dendrogram near cluster 1 reflects a slight twigs of subcluster A mirrored only epidemiological traits. resemblance to some strains of subclusters B1 through B3. No demarcation problem with respect to other taxa was However, they were very dissimilar to P. fragi 569T, and recognized for strains in subclusters A and B3 (the latter their taxonomic position could not be established. comprised all five fluorescent strains found in the P. fragi Cluster 5, P. lundensis. Cluster 5 comprised 40 strains; all complex). The nearest significant cluster for almost all of the of these strains were derived from meat, and one of them strains in subclusters A and B3 was cluster 5 (Pseudornonas was the type strain of P. Zundensis, strain 573 (= CCM 3503). Zundensis). However, cluster 5 was relatively distant and On the basis of the present study, a previous numerical study posed no taxonomic or diagnostic problems. Instead, two (20), and genetic evidence (J. Ursing, Curr. Microbiol., in rather vigorous strains, strains 390 and 491, resembled press), the name P. lundensis is proposed for these orga- cluster 11 (P.jhorescens biovar 4), but in these cases the nisms in the accompanying paper (21). Although only 80% of separating distances were quite good. the strains produced visually scoreable fluorescent pigments In contrast, the distances from strains in subclusters B1 on King B medium plates (Table 5), all of the strains and B2 to P. fragi 569T (Table 1) were only marginally less produced pyoverdines when they were tested by spectro- than the distance to the center of cluster 11 (P.jluorescens fluorimetric methods (data not shown). Most strains strongly biovar 4). Hence, no clear-cut delimitation of the species P. liquefied gelatin; this test and the test for production of fragi was obtained. fluorescent pigments were the only conventional tests that Five strains, including the only environmental strain of could be used for differentiation between cluster 5 and the P. cluster 1 (strain 540), joined the cluster close to the fusion fragi complex. A high degree of similarity between these two level limit of 75%. As expected, these strains exhibited some clusters was also evident in the pattern of carbon compound aberrant reactions. As for strain 416, the long HMO distance assimilation. In general, substances used by P. Zundensis (Table 1) indicates that the merging of this strain into cluster were also used by members of the P. fragi complex. The 1 may tell us more about the degree of distortion of the main difference was the more limited spectrum of com- clustering method than about the actual taxonomic posi- pounds utilized by P. lundensis, which was not able to utilize tion. D-xylose, sugar acids, quinate, and hydroxy-L-proline (Table Seven strains joined cluster 1 at levels outside the 75% 5). Thus, the vigor of the strains averaged only about 30%. limit but before the merging of clusters 1 and 5. Three Four beef isolates joined cluster 5 at similarity levels of VOL.36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 263

TABLE 4. Sources and assimilation vigor of strains belonging to Clusters 6 through 18, the fluorescent supercluster. The clusters 2 through 4 and 19 through 25 and straggler strains fluorescent supercluster comprised 84 strains of P. Assimilation fluorescens, P. putida, and allied bacteria. A total of 29 Strain Cluster Source and/or name as receiveda vigor (%) strains were derived from meat (15% of the meat isolates), 25 strains were derived from soil (96% of the soil isolates), and 572 P. fragi MT141 (turkey)b 48 601 P. fragi D167 (clinical isolate)c 35 16 strains were derived from water (67% of the water 392 2 Beef, Kalmar 46 isolates). All four recognized biovars of P.fluorescens were 449 2 Pork, Tomelilla 48 found among the isolates. The characteristics of the biovars 391 3 Beef, Kalmar 36 are shown in Table 5. These characteristics were concordant 527 3 River water 35 with the descriptions of the biovars, although the assimila- 605 P. fragi PI120 (clinical isolate)c 46 tion frequencies for strains in this study were higher on 302 4 Beef, Kavlinge 28 meso-tartrate and lower on sucrose than the values reported 351 4 Beef, Kristianstad 24 previously (24, 32). The first rather straggly branch of the 362 4 Beef, Savsjo 28 supercluster (Fig. 2), extending from cluster 6 to cluster 9, 395 Beef, Kalmar 29 553T 19 P. aeruginosa CCM 1960T 47 consisted of high-vigor strains. They were typically capable 554 19 P. aeruginosa ATCC 15442 47 of assimilating 55 to 60% of the carbon sources tested, 555 19 P. aeruginosa ATCC 19154 45 including a variety of alcohols. 556 19 P. aeruginosa ATCC 31156 48 Cluster 6, which was identified as P.fluorescens biovar 3, 591 Pseudomonas sp. strain ATCC 19151 38 was centered around reference strain 566 and included four 516 Clay 65 meat isolates, as well as the type strain of Pseudomonas 602 P. fragi PR366 (clinical isolate)c 65 taetrofens,strain 594. The characteristics of the latter strain 581 P. indigofera DSM 50166 69 closely matched those of reference strain 566. The distance 592 Pseudomonas sp. strain ATCC 27109 65 between these two strains was only 5%. These strains, 585T Pseudomonas mesophilica DSM 47 1708T together with the two beef isolates (Table 3), represented a 563= Pseudomonas delajeldii DSM 27 biovar 3 branch that was capable of assimilating higher 50403T dicarboxylic acids. The two pork isolates in cluster 6 lacked 577T 20 P. glathei CCM 2742T 44 this capacity. 578 20 P. glathei CCM 2744 40 Cluster 7 contained two highly vigorous beef isolates that 579T Pseudomonas huttiensis NCIB 9462T 37 very effectively assimilated 2-hydroxy-benzoate (salicylate) 526 Lake water 31 and some other compounds that are seldom utilized by P. 537 River water 35 fluorescens. Otherwise, these strains conformed fairly well 539 River water 27 to the description of biovar 2 (24, 32). They were located at 547 21 Tap water, As, Norway 29 a distance of 20% from the biovar 2 reference strain but 583T 21 P. mephitica NCIB 9672T 28 557 22 Clinical isolated 31 joined cluster 8 outside the 75% limit and because of this 575 22 Clinical isolated 35 were not included among the biovar 2 strains in Table 5. 59gT 23 Aeromonas hydrophila CCM 1242T 15 Cluster 8, which was identified as P.fluorescens biovar 2, mT 23 Aeromonas sobria CCM 2807* 18 comprised four environmental strains and biovar 2 reference 599 Aeromonas sp. strain MT60 (pork)b 37 strain 565 (Table 3). Except for assimilation of histamine, the 551T 24 Pseudomonas acidovorans DSM 39T 40 strains of this cluster closely matched the description of 552 24 Pseudomonas acidovorans CCM 283 43 biovar 2 (24, 32). 59ST Pseudomonas testosteroni CCM 33 The remaining part of the highly vigorous first branch of 1931T the fluorescent supercluster consisted of six straggler strains 558T P. alcaligenes CCM 26ST 13 580T P. indigofera ATCC 19706T 20 and the two P. putida strains in cluster 9 (Table 3). The 587T Pseudomonas oleovorans DSM 24 stragglers could not be identified, and the characteristics of 104ST the P. putida strains used in this study have been reported 588T Pseudomonas pseudoalcaligenes 22 previously (20). DSM 5018fIT The largest cluster within the fluorescent supercluster was 582 Clinical isolated 20 cluster 10. This cluster was identified as P. fluorescens 538 Lake water 21 biovar 1 and comprised 27 strains; 21 of these strains were 550 Adhesive growth 19 derived from meat. The type strains of P.fluorescens (strain 401 Pork fat, Kavlinge 10 564) and Pseudomonas synxantha (strain 593) both joined 447 25 Pork, Tomelilla 13 597 25 Alteromonas putrefaciens MT145 15 cluster 10 above the 75% level (Fig. 2). Most strains closely (turkey)b resembled typical biovar 1 strains (Le., phenon A4a of 584 P. mephitica NCIB 10955 10 Sneath et al. [31]). The following three strains did not 596T Alteromonas putrefaciens ATCC 8 resemble the typical biovar 1 strains: strain 474, due to low 8071T vigor; and strains 467 and 536, which more closely resembled phenon A4b of Sneath et al. (31). a Unless otherwise stated, all samples were from Sweden. See reference 20. Cluster 11 comprised 16 strains, which mainly were soil Obtained from Statens Seruminstitut, Copenhagen, Denmark. isolates (Table 3). The characteristics of this cluster some- Isolated by G. Kronvall, Hospital of Lund, Lund, Sweden. what differed from the description of P.fluorescens biovar 4 (e.g., in the assimilation pattern of butyrate, L-tartrate and a less than 75% but well before the merging of clusters 1and 5. few alcohols) (Table 5). However, a substantial part of the Three fluorescent strains that fused together as a tight current description is based on the results of Stanier et al. cluster, cluster 4, were phenotypically related to P. (32), who included only two biovar 4 strains. In view of the lundensis, whereas nonfluorescent strain 395 was less re- scarcity of data plus the fact that biovar 4 reference strain lated (Table 4). 567, one of the strains of Stanier et al., nicely joined cluster 264 MOLIN AND TERNSTROM INT. J. SYST.BACTERIOL.

0 C Perc en t ag e s i m i la rif y .-C 2 100 90 80 70 60 c I v) 1 I I 1 I I I I I I

I I I I I I I I I I I I I I I I I I I I

I I I I LhI I I I lc,IL I I I 1 I

I I I I I I I I I

I I I

I 1t-i

I 1 I I I I I 100 90 80 70 60 FIG. 1. Phenetic dendrogram showing the relationships among clusters 1 through 3 based on SJ coefficients and clustering by the unweighted pair group method.

11 (Fig. 1 and Table 3), we identified cluster 11 as P. biotypes D and E). Phenotypically, the type strains of these fluorescens biovar 4 in despite the aberrant reactions men- species were very closely related (Table 3), and the centroid tioned above. distances also showed that cluster 12 was positioned rather Cluster 12, a three-member tight cluster, consisted of type close to typical P. fluorescens (i.e., biovar 1) (Table 6). and reference strains of Pseudomonas chlororaphis and The remaining strains in the fluorescent supercluster ei- Pseudomonas aureofaciens (formerly P. fluorescens ther were intermediates between different biovars or could VOL. 36. 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 265

0 L C Percenfage similarity 9) c C In .- 3 - c.2! 100 90 80 70 60 0 v) I I I I I I I 4 I I

11 I 1

7 I I 1 I!1

I I

I I I - I I 1 1 I I I I I I I 11 - I I- I I 12 13

17c

20 c

23 24 c I I I

25c I 1-1 I I I I I I 100 90 80 70 60 FIG. 2. Phenetic dendrogram showing the relationships among clusters 4 through 25 based on SJ coefficients and clustering by the unweighted pair group method. 266 MOLIN AND TERNSTROM INT. J. SYST.BACTERIOL.

TABLE 5. Frequencies of positive characteristics found in significant taxa" P.fluo- P.fluo- P. fluo- P.fluo- P. aureofa- P.fragi P. lun- rescens rescens rescens rescens ciens and P. aeru- P. glathei '* complex densis biovar 1 biovar 2 biovar 3 biovar 4 P. chloror- ginosa Characteristic (cluster 1; (cluster 5; (cluster 10; (cluster 8; (cluster 6; (cluster 11; aphis (cluster 19; '''~s~~~:";(cluster 21; n = 131) n = 40) n = 27) n = 5) n = 6) n = 16) (cluster 12; n = 4) n = 2) n = 3) Cultural characteristics Motility 98b 100 100 100 100 100 100 100 100 100 Spreading growth 0 0 26 0 0 0 0 0 0 0 Hemol y sis 1 5 63 0 0 6 0 100 0 0 Fluorescent pigments 4 80 96 100 100 64 100 100 0 0 Green pigments 0 0 0 0 0 0 0 75 0 0 Pink pigments 0 0 0 0 17 0 0 0 0 0 Yellow or orange pigments 0 0 0 0 0 0 67 25 0 0 Growth at or in the presence Of 4°C 100 100 100 100 100 100 100 0 0 100 37°C 7 42 0 0 0 0 67 100 0 100 42°C 0 0 0 0 0 0 0 100 0 0 4% NaCl 100 100 100 40 100 25 100 100 0 0 5% NaCl 99 100 100 0 83 6 100 100 0 0 Biochemical tests Arginine dihydrolase 94 100 100 100 83 94 100 100 0 0 Esculin hydrolysis 1 0 0 0 0 0 0 0 0 0 NO3 --* N2 0 0 0 60 67 25 0 100 0 0 Ornithine decarboxylase 1 0 0 0 0 0 0 0 0 0 Phosphatase 0 0 0 0 0 0 0 50 50 50 Polysaccharides from 1 0 44 20 0 50 100 0 0 0 sucrose Urease 76 52 59 20 17 25 33 50 0 0 Degradation of: Casein 2 40 93 80 100 62 67 75 0 0 DNA 0 0 15 0 0 0 0 0 0 0 Egg yolk 30 72 100 100 100 94 100 100 0 0 Gelatin 19 90 96 80 100 94 100 100 0 50 Tween 20 18 2 93 0 100 6 100 75 100 0 Tween 80 14 2 96 60 100 50 100 100 100 50 Acid produced from: L- Arabinose 100 100 100 100 100 100 100 100 0 100 Cellobiose 100 100 41 0 0 12 0 0 0 0 D-Fructose 1 0 4 0 0 6 0 0 0 0 D-Galactose 100 100 100 100 100 94 100 100 0 0 Glucitol 0 0 18 0 0 0 0 0 0 0 D-Glucose 100 100 100 100 100 100 100 100 0 0 Glycerol 16 22 33 0 33 0 0 0 0 0 Maltose 100 100 4 0 0 0 0 0 0 100 D-Mannitol 2 0 33 0 0 0 0 0 0 0 D-Mannose 100 100 100 100 100 100 100 100 0 0 Melibiose 100 100 100 100 100 94 100 50 0 0 Raf€inose 0 0 0 0 0 0 100 0 0 0 L-Rhamnose 49 42 7 0 50 0 0 0 0 0 D-Ribose 99 100 100 100 100 100 100 100 0 100 Sucrose 0 0 41 20 0 25 100 0 0 0 Trehalose 1 0 7 0 0 0 0 0 0 0 D-Xylose 99 100 100 100 100 100 100 100 50 100 Assimilation of carbohydrates as sole carbon sources D- Arabinose 95 90 4 0 0 0 0 0 100 0 L- Arabinose 66 100 100 100 0 100 67 0 100 100 Arbutin 0 0 0 0 0 0 0 0 0 100 Cellobiose 2 0 0 0 0 0 0 0 0 100 Dextrin 3 0 0 0 0 0 0 0 0 50 D-Fructose 100 100 96 100 100 100 100 100 100 100 D-Galactonate 37 0 93 100 100 100 100 0 100 0 D-Galactose' 41 20 100 100 100 100 100 0 100 100 D-Gluconate 100 90 100 100 83 100 100 100 100 0 D-Glucose 6-phosphate 1 0 7 0 17 0 0 0 100 100 D-Glucuronate 98 0 100 100 0 62 0 0 100 0 Lactose 0 0 0 0 0 0 0 0 100 0

Continued on following puge VOL.36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 267

TABLE 5-Conrinued P.jlrio- P.,jluo- P.,jliro- P.,flrro- P. arrreqftr- P. ji(i,qi P. Irrn- I’PSCPJ~S wscens rcscetis rcscetis ciens and P. tierir- p. g/

Continued on following puge 268 MOLIN AND TERNSTROM INT. J. SYST.BACTERIOL.

TABLE 5-Continued P. jlrio- P.jlrro- P..flrro- P.jrro- P. iirirci~f~i- P, fi.qi P. Iirn- rescens rescens rcsc'ens rescens ciens and P. cierrr- p. glnti1pi P. mephi- complex densis biovar 1 biovar 2 biovar 3 biovar 4 P. chloiw- ginostr ticu Characteristic (cluster 1; (cluster 5; (cluster 10; (cluster 8; (cluster 6; (cluster 11; rrphis (cluster 19; (c'l~s~~~O'(cluster 21; II = 131) n = 40) ti = 27) n = 5) n = 6) I? = 16) (cluster 12: n = 4) I1 = 2) I1 = 3) 1-Butanol' 17 82 7 100 100 31 33 100 100 0 2-Bu tanol' 0 0 0 80 67 0 0 100 0 0 i-Erythritol 1 2 85 40 100 6 0 0 0 0 Ethanol 1 5 7 100 100 0 0 100 0 50 Galactitol 0 0 0 0 0 0 0 0 100 0 Geraniol' 0 0 0 0 17 0 0 25 0 d Gluqitol 0 0 93 80 0 94 0 0 100 100 Glycerol 100 98 100 100 100 100 100 100 0 100 1-Hexanol 2 22 7 100 100 25 67 100 0 0 meso-Inositol 30 88 100 100 100 88 100 0 50 100 D-Mannitol 72 0 96 100 100 94 100 100 100 100 Methanol' 0 0 0 80 67 0 0 25 0 0 3-Methyl-1-butanol 1 0 7 100 100 6 0 0 0 100 2-Methyl-2,4-pentanediolc 0 0 0 0 33 0 0 0 0 0 2-Meth yl-l-propanol' 0 0 0 100 83 0 0 25 0 0 1-Eentanol' 0 0 7 20 67 0 0 0 0 0 Propane-l,2-diol 5 2 7 100 100 0 0 100 0 0 1-Propanol' 37 62 7 100 100 0 0 100 0 50 2-Propanol 0 0 4 100 100 0 0 100 0 0 Ribitol 0 0 100 0 100 0 33 0 100 0 Xylitol 1 0 100 0 100 0 0 0 100 100 Assimilation of miscella- neous nonnitrogenous compounds as sole carbon sources 3-H ydroxy-2-butanone 44 2 22 100 83 12 67 100 0 0 Phenol 0 0 0 0 0 6 0 0 100 0 Assimilation of aliphatic amino acids as sole carbon sources L-a- Alanine 100 100 100 100 100 100 67 100 100 100 P- Alanine 99 100 100 100 100 100 100 100 100 50 DL-ZAminobut yrate 0 0 4 20 83 0 0 0 0 50 D~-3-Aminobutyrate' 0 0 0 20 33 0 0 100 50 50 4-Aminobutyrate 100 100 100 100 100 100 100 100 100 0 DL-g- Aminohexanoate' 0 0 0 20 0 25 0 0 0 0 DL-2-Aminppentanoate" 0 0 4 20 0 6 0 50 0 0 5- Aminopentanoate 48 100 56 100 100 100 67 100 50 0 L- Arginine 99 100 100 100 100 94 100 100 100 0 L- Aspartate 100 100 100 100 100 100 100 100 0 100 L-Citmlline 8 0 78 40 100 31 67 0 0 0 L-C ysteine 0 0 0 0 0 6 0 0 0 0 L-Glutamate 100 100 100 100 100 100 67 100 100 100 Glycine 72 0 0 20 33 12 33 100 0 0 L-Isoleucined 90 95 100 100 100 100 100 100 0 0 L-Leucine 98 98 100 100 100 100 100 100 50 0 L-Lysine 86 95 70 100 83 '94 100 100 100 0 L-Ornithined 99 100 96 100 100 88 100 100 100 0 L-Serinec,d 76 15 96 100 100 94 100 25 0 100 m-Valine 80 98 100 100 100 100 100 75 0 100 Assimilation of aromatic amino acids as sole carbon sources L-Histidine 98 100 100 80 100 94 100 75 100 50 H y drox y -L-proline 96 5 100 80 67 62 100 75 50 0 L-Methionine 0 0 41 0 17 0 0 0 0 0 L-Phen ylalanine 100 100 89 80 100 100 100 67 100 0 L-Proline 100 100 100 100 100 100 100 100 100 0 L-Tryptophan 0 0 96 20 100 31 100 100 50 0 DL-Tyrosine 100 100 100 100 100 100 100 100 50 0 Assimilation of amines as sole carbon sources 2-Aminodeox yglucose 26 2 96 100 100 69 100 100 100 100 2-Aminoethanol' 87 100 100 80 83 12 100 100 50 0

Continued on following puge VOL. 36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 269

TABLE 5-Conrinued P.,flue- P. flrro- P.jlrro- P.jlrro- P. ciureof& P. frugi P. Irm- reseem wscctis rescens resectis ciens and P. cienr- P. giatiiei p. Characteristic complex dctisis biovar 1 biovar 2 biovar 3 biovar 4 P. chioror- ginosti tica (cluster 1: (cluster 5: (cluster 10; (cluster 8; (cluster 6; (cluster 11; ciphis (cluster 19; ('luster *" (cluster 21; II = 131) 11 = 40) ti = 27) ti = 5) ti = 6) n = 16) (cluster 12; n = 4) = 2, n = 2) n = 3) a-Aminotoluene 0 0 0 20 0 12 0 0 0 0 Histamine diphosphate 3 0 67 100 33 25 100 100 0 0 Putrescine 100 100 100 100 100 100 100 100 0 0 Taurine 0 0 0 20 33 0 0 0 100 100 Tryptamine 0 0 4 40 33 6 0 0 50 0 Assimilation of miscella- neous nitrogenous compounds as sole carbon sources Acetamide 0 0 0 0 0 0 0 100 0 0 Anthranilate 0 0 52 0 3 0 0 50 0 0 Betaine 98 98 100 100 100 100 100 100 100 50 D L-Carni tine 83 0 93 100 100 100 100 100 50 0 Carnosined 75 32 96 80 100 0 100 100 0 0 Creatine 95 78 0 0 17 6 0 0 100 0 Creatinine" 2 0 0 0 0 6 0 0 50 0 Cystine 0 0 0 0 0 6 0 0 0 0 HippuratecVd 92 0 0 0 67 0 33 50 100 0 Inosine 97 2 100 100 100 100 100 100 0 100 K y n u re n at e 2 0 22 20 100 0 0 25 0 0 Nicotinate 14 0 30 0 0 0 0 0 0 0 SarcosineC*d 75 92 89 100 ioo 100 100 100 0 0 Tauroc holate 95 88 7 100 67 0 0 100 0 0 Testosterone 1 0 0 20 0 0 0 0 0 6; Trigonelline 0 0 4 0 0 50 0 0 0 0

a All strains were gram negative, nonsporulating, rod shaped, and positive for the following characteristics: production of catalase and cytochroqe c oxidase; and assimilation of acetate, L-asparagine, fumarate, pyruvate, add succhinate. All strains were negative for the following characteristics: methyl red and Voges- Proskauer reactions; decarboxylation of L-lysine; hydrolysis of esculin and starch; production of hydrogen sulfide and indole; production of acid from dextrin, glucose (anaerobically), salicin, starch, and xylitol; and assimilation of alginate, 3-amino-~-tyrosine,amygdalin, crotonate, 1,2-ethanediol, glycolate, 1- hydroxynaphthalene, inulin, maleate, mandelate, melezitose, menthol, cw-methyl-D-glucoside, oxalate, palmitate, 2,6-pyridine dicarboxylate, pyridoxal hydro- chloride, riboflavine, L-sorbose, D-tartrate, D-tryptophan, isovalerate, and L-xylose. The values are percentages of positive strains. Scoring was sometimes diacult. There was a high incidence of mutant colonies.

not be identified. However, cluster 15 could probably be The characteristics and centroid distances of clusters 19, 20 ascribed to the less vigorous branch of biovar 3, and cluster (Pseudomonas gfathei),and 21 (P. mephitica) are shown in 16 somewhat resembled phenon A4d of Sneath et al. (31). Tables 5 and 6. The frequencies of positive test reactions for Clusters 19 through 25. The origin and assimilation vigor of the type and reference strains of P. gfathei were significantly the remaining 39 strains are summarized in Table 4. Cluster lower than previously reported (34). Thus, it would be 19, a tight cluster containing four Pseudomonas aeruginosa impossible to identify P. gfathei by using the present inves- strains, bore some resemblance to the high-vigor biovars of tigation techniques in combination with the original descrip- P.jluorescens (Table 6). However, other strains in this part tion. of the dendrogram were very dissimilar to clusters 1through The type strain of the once food-associated and poorly 18, and, except for cluster 19 strains, none was fluorescent. described species P. mephitica (14)joined a tap water isolate

TABLE 6. Distances between the centroids of significant taxa Distance from the centroid of cluster: Cluster Tawn 1 5 10 8 6 11 12 19 20 21 1 P. .fiagi complex 0 5 P. hndensis 0.28 0 10 P. j7uoresc.cn.s biovar 1 0.32 0.39 0 8 P. jiwrcscens biovar 2 0.37 0.43 0.31 0 6 P. j7iuwescen.s biovar 3 0.41 0.44 0.32 0.29 0 11 P. j7uorescen.s biovar 4 0.29 0.35 0.24 0.27 0.36 0 12 P. aureofuciens-P.~,iiloi.~)i.cipiii.~ 0.35 0.40 0.26 0.33 0.34 0.25 0 19 P. aeruginasci 0.43 0.44 0.43 0.38 0.35 0.42 0.38 0 20 P. glurhei 0.47 0.52 0.48 0.51 0.53 0.45 0.51 0.57 0 21 P. mepliiticci 0.50 0.49 0.51 0.53 0.55 0.46 0.53 0.58 0.50 0 270 MOLIN AND TERNSTROM INT. J. SYST.BACTERIOL. to form cluster 21. Although less vigorous than most Pseu- Number of changes in characters domonas spp. studied, this species assimilated some ring 0 10 20 30 40 structure glycosides (Table 5), a characteristic that may I I I I 1 serve a diagnostic purpose. (a) The remaining straggly area was mainly populated by type and reference strains of various Pseudomonas spp. to which A- P. lundensis no field strain bore any resemblance or by nonpseudo- fl I------P. fragi-complex monads. The latter group included five fermentative strains I I within or in the vicinity of clusters 22 and 23. These strains I P. fluor. 3 I joined together well before the merging into the main fusion. I P. fluor. 2 582 I Other nonpseudomonads were straggler strain (probably I ------a Acinetobacter sp.), strain 550 (probably a Flavobacterium P. mephitica sp.), and the five hydrogen sulfide-producing alteromonads that were the last strains to join the tree. This final branch included two meat isolates and a misnamed collection strain, 0 10 20 30 40 strain 584 (= NCIB 10955) (P. rnephitica). Another probably I I 1 I 1 misnamed collection strain, the extremely vigorous strain (b) P. fluor. 1 581 (= DSM 50166) (Pseudomonas indigofera), showed no P. fluor. 4 I------resemblance to the type strain of P. indigofera and further- P. fluor. 3 more was so atypical that its status as a Pseudomonas sp. is doubtful. P. fluor. 2 Data for individual strains and small clusters are not given P. lundensis in this paper but can be obtained from us. Representative P. fragi-complex strains belonging to clusters 1, 5, 6, 8, 10, and 11 have been deposited with the Czechoslovak Collection of Microorga- I ------P. mephitica nisms. Phylogeny. Based on HMOs, the phylogenetic relationships among the different meat-associated Pseudornonas 0 10 20 30 40 clusters were calculated. Four equally parsimonious trees r I I 1 1 were obtained (Fig. 3). These trees were rooted by using P. P. fluor. 1 mephitica as an outgroup. However, we are not suggesting P. fluor. 4 that P. mephitica is the ancestor of the meat clusters; this P. lundensis organism is included only as a reference point for the _------calculations (i.e., the trees are in the strict sense unrooted). P. fragi-complex Including the outgroup, all of the trees were built by 76 P. fluor. 3 stepwise changes in the test profile. Trees a and b involved P. fluor. 2 12 changes between the outgroup and the hypothetical L ------ancestor, while trees c and d needed 11 and 8 changes, P. mephitica respectively (Fig. 3). Whatever tree is the most trustworthy, our phylogenetic estimate indicated that (i) biovars 1and 4 of P. fluorexens P. fragi P. are more closely related to and 0 10 20 30 40 lundensis than biovars 2 and 3 are, and (ii) P. fluorescens I 1 I I I biovar 4 is a conservative organism, while biovar 3 is rapidly P. fluor. 4 evolving. P. fluor. 2 DISCUSSION P. fluor. 3 Methodology. Growth on sole carbon sources has proven ------P. fluor. 1 to be a powerful and reliable taxonomic instrument in the P. fragi-complex study of pseudomonads. Among the advantages of this P. lundensis method is the high degree of resolution that can be obtained when a large battery of unrelated carb'on compounds is used. L------P. mephitica However, to make full use of the potential of the method, workers are at present restricted to manual techniques. FIG. 3. Four equally parsimonious trees representing possible phylogenetic relationships among the HMOs of the meat-associated Handling perhaps 100 or more tests in such a way is a tedious clusters. Trees a through d were rooted by including P. rnephifica as task and limits the use of the method. Another drawback is an outgroup in the calculations. P. fluor., P. fluorexens. the difficulties experienced when the results are scored. More or less pronounced background gt-owth is common; hence, inoculated mineral medium supplemented with agar is always incorporated as a negative reference. However, ogy because of the need,for a sensitive and complex photo- interference due to impurities in the carbon sources remain metric detectian unit. A fully automated method in which a undetected. Such impurities can disturb the scoring by simple and inexpensive detector is used would be feasible if acting in the following three ways: as growth substrates, as the reference plates could be omitted. In this present paper growth stimulants, and as catalyzing agents. Hence, the we show that the reference plates can indeed be omitted negative control used is not altogether satisfactory. without seriously affecting the reproducibility of the method. The use of reference plates is also an obstacle for the The only problem experienced was with the weakly growing development of an automated assimilation testing methodol- strains of P. glathei. Comparing the characteristics for this VOL. 36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 271

species in Table 5 with the original description given by Zolg strains showing atypical reactions and (ii) a shortage of and Ottow (34), we found that in the present study we appropriate characteristics for diagnostic purposes, The consistently recorded considerably fewer positive features. latter may be somewhat less pronounced in view of the new This does not necessarily disqualify the use of the modified differentiation tests proposed above. method for identifying less luxuriously growing strains since P. lundensis and the P. fragi complex. P. lundensis and the a modified description (such as the one in Table 6 for P. P.fragi complex are phenotypically related to P.fluorescens glathei) is probably adequate. However, the problem should (this study). This rather close relationship is supported by be kept in mind. evidence from deoxyribonucleic acid (DNA)-DNA hybrid- In any case, a fully automated process for plating and ization experiments (Ursing, in press). However, strains of scoring a large number of assimilation tests would be a P. lundensis and the P.fragi complex are usually much less desirable tool for use in the identification of pseudomonads. vigorous than strains of P. Jluorescens. Differentiation be- The full resolution power of the assimilation methodology tween the two superclusters identified in the present study could then be used not only for research but also for routine can be achieved by using several characteristics (Table 5). purposes. Although P.Jluorescens and allied bacteria do constitute a Fluorescent supercluster. The fluorescent supercluster significant part of the spoilage microflora on meat, our comprises seven recognized taxa corresponding to the hier- results clearly brings out the fact that members of the P. archic level of the species (i.e. the two biovars of P. putida, fragi complex and P. lundensis were the predominant orga- the four biovars of P.fluorescens, and a single taxon which nisms in almost 85% of the meat samples tested. includes both P. aureofaciens and P. chlororaphis). These P. lundensis, the second most important meat-spoiling groups are of obvious ecological significance. Of the 50 species, was as phenotypically homogeneous as previously environmental strains isolated, 45 were members of the suggested (20). DNA-DNA hybridization experiments also fluorescent supercluster. Including meat isolates, the fluo- established that this phenon is a tight genotypic species rescent supercluster comprised 69 field strains; 47 (68%) of (Ursing, in press). This new species is described in the these could be assigned to one of the four biovars of P. accompanying paper (21). Jluorescens described by Stanier et al. (32). As an overall A common feature of strains in the fluorescent superclus- figure, this seems quite acceptable; however, whereas al- ter and P. lundensis is the production of fluorescent pig- most all of the meat isolates (93%) could be assigned, only ments. Although not all strains of P. lundensis are capable of 33% of the aquatic strains and 60% of the soil strains could producing visually scoreable pigments on King B medium, be assigned to the recognized biovars. This came as a all of the strains investigated so far do so when they are surprise since Stanier and co-workers actually based their tested by more sensitive methods (data not shown). material on environmental, especially aquatic, strains and It is conceivable that meat strains of P. lundensis may did not include a single meat isolate in their study. However, have been misidentified previously as P.Jluorescens because the fact that the four major clusters within the fluorescent of the production of fluorescent pigments and proteases, supercluster actually did correspond to current subdivisions characteristics that often serve as identification keys. must be regarded as support for the classification framework The taxonomic value of the fluorescent pigments has long provided by Stanier et al. (32). been discussed. Using spectrofluorimetric scanning meth- The description of biovar 4 (biotype F) of Stanier et al. ods, we detected fluorescent pigments among all of the was originally based on the study of only two strains. In the strains belonging to the fluorescent supercluster and P. present study 16 isolates were assigned to biovar 4. Thus, lundensis in this study (data not shown). In contrast, no the phenotypic foundation for this biovar has been substan- strain outside subcluster B3 in the P. fragi complex pro- tially strengthened. duced any pigment, indicating that this characteristic has The selection of commonly used assimilation characteris- substantial taxonomic value. tics for differentiation between biovars (24) proved, with the Recent findings concerning the complexity of the gene exception of butyrate and sucrose, to be reasonably ade- systems coding for these pigments (pyoverdines) also point quate. In the present study, using an extended collection of in the same direction (23). The pyoverdines act as iron- carbon sources, we found at least six new assimilation scavenging proteins. The fluorescent emission signal of all of characteristics with potential diagnostic value. These char- the tested representatives of the P.Jluorescens biovars and acteristics were assimilation of carnosine, glucuronate, 3- P. lundensis isolated in this study were quenched by ferric hydroxy-2-butanone (acetoin), 3-methyl-1-butanol,taurocho- ions but not by ferrous ions (data not shown). late, and xylitol. Furthermore, the possible taxonomic sig- Two of every three meat isolates in the present study nificance of acid production from raffinose (the three strains belonged to the P.fragi complex (cluster 1).Unfortunately, of P. aureofaciens and P. chlororaphis were the only strains these isolates had a less clear-cut phenotypic profile than P. among the whole collection that produced acid from this lundensis. It is possible to sort out the main branch of this sugar) and resistance to sodium chloride should be further complex (in this study, subcluster A) as P. fragi sensu investigated. stricto. This branch is phenotypically reasonably homoge- Champion et al. (4) concluded that a high congruence can neous, and all strains share a high degree of phenotypic be found between phenotypically and genotypically assigned homology with the type strain of P. fragi. Furthermore, (i) subspecies of P. Jluorescens (including P. aureofaciens-P. its phenotypic profile seems to be very stable when the chlororaphis). Of 87 phenotypically classified strains, 81 results of the present numerical analysis are compared with could be assigned to a corresponding genotype, indicating previous results (20) and (ii) DNA-DNA hybridization ex- that the phenotype coincided with the genotype. Unfortu- periments also revealed high levels of homology between all nately, however, the errant six strains included the type of the tested strains within this branch and the type strain of strain of P. Jluorescens. The type strain was not mis- P.fragi (Ursing, in press). matched, only nongroupable, but even so this finding under- Although a clarifying classification of the P.fragi complex scores the obstacles for elevating the biovars to species would be very desirable, in our opinion the obstacle posed level. Other difficulties in this task are (i) the vast number of by the strains outside subcluster A must place an emended 272 MOLIN AND TERNSTROM INT. J. SYST. BACTERIOL.

TABLE 7. Differential tests for the subclusters of cluster 1 edly be misidentified as P. putida if a limited, non- ‘X Of positive strains in subcluster: assimilation-based identification scheme were used. Characteristic A B1 B2 B3 Genus concept. Historically primarily a dumping ground (11 = 93) (11 = 20) (11 = 8) (n = 5) for various nondescript organisms, the genus Pseudomonas today provides an intriguing example of bacteriological Fluorescent pigments 0 0 0 100 systematics. The taxonomy of certain pseudomonads is Egg yolk reaction 42 0 0 0 Gelatinase 13 30 88 0 extensively studied by using polymethodological ap- Acid from glycerol 3 5s 62 0 proaches, including phenotypic studies (32), DNA-DNA Acid from L-rhamnose 31 100 100 60 hybridization and ribosomal ribonucleic acid (rRNA)-DNA Assimilation of hybridization (6, 25, 27), protein analysis (4), and enzyme L-Arabinose 55 100 100 100 patterns (3). Nevertheless, the present standing of pseudo- D-Galactonate 13 100 100 100 monads in taxonomy is not satisfactory. Trehalose 95 0 0 0 The lack of useful diagnostic criteria for separating dif- Itaconate 89 0 0 100 ferent groups of pseudomonads has been an obstacle for 4-H ydroxybenzoate 86 95 88 0 obtaining a firm taxonomic structure. It has also been the meso-Tartrate 90 20 0 0 Pseudomonas meso-Inositol 5 100 100 100 main reason for not restricting the genus to Propane-l,2-diol 0 0 0 100 what is known as rRNA group 1 (25), an action otherwise L-Citrulline 0 0 100 0 advocated by some taxonomists (7). However, this lack of DL-Valine 98 0 88 100 differentiating phenotypic characteristics is hardly surprising 2-Aminodeox yglucose 4 100 75 0 when we take into account the wide phenotypic range of Nicotinate 0 70 0 0 rRNA group 1 species. In the present study the distances between the nonfluorescent rRNA group 1 member Pseu- domonas alcaligenes and the fluorescent members (P. aeruginosa, P. aureofaciens, P. chlororaphis, P. fluorescens, description of P. fragi in the future. In the meantime, the and P. putida) approached 80%; i.e., the test result patterns characteristics listed in Table 7 can be used to differentiate were almost inverted. Since rRNA group 1 currently com- between subclusters A and B. prises only 12 well-characterized species (24) and hitherto The authenticity of the aggregate of subclusters B1 more than 30 of the vast number of badly characterized through B3 is sustained when the previous numerical analy- Pseudomonas nomenspecies (some of which are likely to sis is examined (20), in which 25 strains would have been turn out to be authentic species) have been assigned to incorporated into these subclusters if the P.fragi cluster had rRNA group 1 (ll), it follows that in the future the pheno- been divided. However, the authenticity of two subclusters, typic range between rRNA group l species may expand even subclusters B1 and B2, becomes doubtful when the same further. Thus, if the genus concept is to be of significance in material is examined. Strains belonging to these two classification, the restriction of Pseudomonads to rRNA subclusters seem to mingle and comprise a single subcluster group 1 in reality seems to be an insufficient action. Instead, (subcluster Bl-B2). Subcluster B3 was represented by only the possibility of breaking down rRNA group 1 into several two strains in the previous study, but both of these strains genera should be considered. conform to the description in Table 7. From a phenotypic Subgroups of rRNA group 1 do exist (27), and they point of view, it is tempting to regard subcluster Bl-B2 and represent a promising starting point for the establishment of subcluster B3 as two biovars of P. fragi, but the genetic new genera. In view of phenotypic data (32; this study), as evidence does not support this view, since all of the well as genotypic data (3, 7, 16; Ursing, in press), one such subcluster B strains tested show about the same level of new genus might be constituted by the P. Jluorescens-P. DNA complementarity toward the type strain of P.fragi as putida complex, the P. fragi complex, and P. lundensis. the type strain of P. chlororaphis does (Ursing, in press). It Species concept. There are obvious problems in drawing is possible that these strains may display a higher degree of lines of demarcation between the different biovars of the P. hybridization with DNA preparations of meat strains in Jluorescens-P. putida complex (31; this study), as well as subcluster A to which they are phenotypically more closely between the different subclusters of the P. fragi complex related than to the type strain. Even so, it is doubtful (this study). Thus, phenotypically, certain branches of the whether they can be placed in the same species; this is two complexes indicate the presence of continuums. Thus, it because of the central role which the type strain occupies in could be that if more strains from more environments were the species concept. The alternative is to elevate the characterized, the continuums might be gradually com- subclusters to one or several new species, but such an action pleted. In agreement with the phenotypic continuum of must await further genetic study due to the fact that the fluorescent pseudomonads, Hildebrand et al. (16) showed relationships among the various strains belonging to that the DNA-DNA hybridization values of this complex subclusters B1 through B3 are currently unknown. Further- form a three-dimensional continuum. The existence of tax- more, strains that are phenotypically intermediate between onomic continuums indicates that the practice of defining a subcluster A and the other subclusters exist, and recent species by a 70% level (2) in DNA hybridization experiments findings from the spoilage of fish suggest a partly different P. reflects an artificial taxonomy. However, the formation of fragi complex than the present complex (Molin and continuums is hardly surprising in view of the Darwinian law Stenstrom, unpublished data). Thus, an emended descrip- of the effect of selection pressure on the creation of species tion of P. fragi based on present knowledge seems prema- and the fact that the microenvironments occupied by, for ture and would probably not serve any useful purpose. example, the psychrotrophic pseudomonads in nature might From an identification point of view, the strains in be assumed to form chains of gradually changing ecological subcluster B3 merit some attention. They are the only strains niches. In addition, horizontal transfer of genetic material in the P. fragi complex that are capable of producing between organisms may further contribute to the formation pyoverdines , and they lack proteases. They would undoubt- of continuums. VOL. 36, 1986 TAXONOMY OF PSYCHROTROPHIC PSEUDOMONAS 273

The continuums are difficult to handle in formal taxon- 5. Davidson, C. M. 1973. Properties of gram negative aerobes omy, where the purpose is to create a simple language for isolated from meats. J. Food Sci. 38:303-305. recognition that is understandable to the general scientific 6. De Vos, P., and J. De Ley. 1983. Intra- and intergeneric community. On the other hand, the fact that continuums are similarities of Pseudomonas and Xanthomonas ribosomal present can hardly be overlooked in taxonomic and ecolog- ribonucleic acid cistrons. Int. J. Syst. Bacteriol. 33:487-509. 7. De Vos, P., A. van Landschoot, and J. De Ley. 1984. The ical research. Thus, this stresses a need for two parallel taxonomic position of the saprophytic members of the non- taxonomic systems, one artificial, to be applied at, for classified Pseudomonas species. Antonie van Leeuwenhoek J. example, the level of routine identification, and one more Microbiol. Serol. 50:301-302. “natural,” to be used in experimental taxonomy 8. Edwards, P. R., and W. H. Ewing. 1972. Identification of Phylogenetic considerations. As shown in this study and Enterobacteriaceae, 3rd ed. Burgess Publishing Co., Minneap- elsewhere (20), P.frugi and P. Zundensis, together with the olis. four biovars of P. fluurescens, are found on spoiled meat; 9. Eichholz, W. 1902. Erdbeerbacillus (Bacteriumfragi). Zentralbl. i.e., these organisms have the ability to reach high popula- Bakteriol. Parasitenkd. Infektionskr. Hyg. Abt. 2 9:425428. 10. Enfors, S.-O., G. Molin, and A. Ternstrom. 1979. Effect of tion densities in this particular environment and in competi- packaging under carbon dioxide, nitrogen or air on the microbial tion with the rest of the microbiological world. This, together flora of pork stored at 4°C. J. Appl. Bacteriol. 47:197-208. with the existing phenotypic and genotypic (Ursing, in press) 11. Goor, M., P. De Vos, M. Gillis, and J. De Ley. 1984. 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