INTERNATIONAL JOURNAL OF SYSTEMATIC BACTERIOLOGY Vol. 24, No. 4 Oct. 1974, p. 534-550 Printed in U.S.A. Copyright 0 1914 International Association of Microbiological Societies Emended Descriptions of the Genus Alcaligenes and of Alcaligenes faecalis and Proposal That tfie Generic Name Achromobacter be Rejected: Status of the Named Species of Alcaligenes and A c h romo bac ter Request for an Opinion MARGARET S. HENDRIE, A. J. HOLDING, and J. M. SHEWAN Torry Research Station, Aberdeen, Scotland, United Kingdom, and Department of Microbiology, University of' Edinburgh, Scotland, United Kingdom The descriptions of the genus Alcaligenes Castellani and Chalmers and Alcaligenes faecalis Castellani and Chalmers have been emended. It is requested that the Judicial Commission issue an Opinion rejecting the name Achromobacter Bergey et al. as a nomen dubium. It is proposed, on the basis of a comparison of type and reference strains, that Alcaligenes denitrificans Leifson and Hugh, Achromobacter arsenoxy- dans-tres Turner, and Alcaligenes odorans (Mhlek and Kazdovii-KoiiSkovii) MBlek et al. be considered as subjective synonyms of A.faecalis. The proposed taxonomic status of all known previously described species of the genera Alcaligenes and Achromobacter is indicated in appendixes. Emendation of description of the genus Aha- Rods or coccoid cells, 0.5 to.0.6 by 1.2 to 2.6 ligenes Castellani and Chalmers. Extensive stud- gm, usually occurring singly. Motile by means of ies on the morphology and physiology of the one to four (occasionally up to eight) flagella; the gram-negative asporogenous rods have been un- flagella may be degenerate. Cells are peritrichous. dertaken in recent years by Baumann et al. (10, No resting stages are known. Gram ntgative. 1 I), De Ley et at. (56-58), Cabassi et al. (38), Chemoorganotrophic; some species are chemo- Samuels et al. (131), and De Ley and Shewan lithotrophic with H2; metabolism is respiratory, (unpublished data). These studies have revealed never fermentative. Molecular oxygen is the final that strictly aerobic. peritrichous bacteria (with electron acceptor. the exception 01' those also possessing anaerobic Strictly aerobic except for some strains that are respiratory mechanisms) should be considered capable of anaerobic respiration in the presence of for inclusion in the genus Alcaligenes. No valid nitrate or nitrite, which act as alternate electron criteria that justify the separation of Achromo- accept0 rs. bacter from Alcaligenes have been established. Most strains (except those of A. aquamarinus) Organisms such as those belonging to Acetobac- have simple nitrogenous nutritional requirements ter, Agrobacterium, or Rhizobium possess these and produce very turbid growth in liquid media characteristics, but they also possess special with ammonium or nitrate salts as the sole nitro,- physiological or ecological properties that ex- gen source; some Strains require organic nitrogen clude them from Alcaligenes and Achromobac- compounds (amino acids and/or vitamins). Gase- ter. These two prime characteristics, therefore, ous. nitrogen is not fixed. exclude from Alcaligenes and Achromobacter Not actively proteolytic in casein or gelatin bacteria that are facultatively anaerobic, nonmo- media. Cellulose, chitin, and agar are not hydro- tile, or polarly flagellated. These bacteria are lyzed. Oxidase is produced (Kovacs test). allocated to the family Enterobacteriaceae, the Optimal temperatures are between 20 and 37 C. Acinetobacter-Moraxella group, and the family All species grow quickly at pH 7.0. Pseudomonadaceae, respectively. The guanine plus cytosine (G + C) content of As a result of these previous studies and of the deoxyribonucleic acid ranges from 58 to 70 unpublished investigations on 300 extant strains of mol%. 270 named species previously classified as belong- Attempts by many workers to isolate a strain ing to either Alcaligenes or Achromobacter, the that possesses the described characteristics of the following emended description of the genus type species of Achromobacter, A. liquefaciens Alcaligenes is proposed. (Eisenberg) Bergey et al., have failed. This lack of 5 34 VOL. 24, 1974 REQUEST FOR AN OPINION 535 a neotype strain has prevented more detailed in- Alcaligenes Castellani and Chalmers 19 I9 (4I): vestigations of the genus from being carried out. “Rods which are either motile by means of Proposed rejection of the generic name Achro- peritrichous flagella or non-motile. Gram-nega- mobacter Bergey et al. The genus named tive. May or may not liquefy gelatin and solidified Achromobacter was first instituted in 1923 by the blood serum. Litmus milk turned alkaline, with or Committee of the Society of American Bacteriolo- without peptonization. Carbohydrates not utilized. gists ( 16) to accommodate nonpathogenic, small to Acetylmethylcarbinol not produced. Chromogene- medium-sized, motile or nonmotile rods that were sis, when it occurs, is grayish-yellow, brownish-yel- aerobic, nonpigmented, and asporogenous and low or yellow. Generally found in the intestinal which occurred principally in soil and water. Such. tracts of vertebrates or in dairy products. The type rods had been described previously by Eisenberg species is Alcaligenes faecalis Castellani and (61), Lehmann and Neumann (loo), Mez (1 lo), Chalmers.” Migula (1 1 I), Chester (44), and Ford (67) under a Achromobacter Bergey et al. 1923 (16): “non- variety of names, including Bacillus liquefaciens pigment-forming (at least no pigment formed on and Bacillus liquidus. It was recognized early (5l), agar or gelatin) rods. Motile by means of peritri- however, that “there seems to be no recognisable chous flagella or non-motile. Gram-negative. Lit- distinction between Alcaligenes and similar orga- mus milk faintly acid to unchanged or alkaline. nisms which were (then) placed in Achromobac- Occur in salt- to fresh-water and in soil. The type ter” and that Achromobacter is an ill-defined species is Achrornobacter liquefaciens (Eisenberg) genus with a possibly unrecognizable type species. Bergey et al.” I:i mosi of theearly work, little or no mention is Although there exists a reference strain of made of the type of flagellation of organisms Alcaligenes faecalis that accords with the original placed in Achromobacter, and only in Bergey’s description of Castellani and Chalmers, there is no Manual (16), when the genus Achromobacter was extant c u 1t u re of A c hrom obacter liq uefaciens , and first named, were other additional characteristics, the most recent attempt (149) to establish a including flagella position, added. A. liquefaciens neotype failed because all extant cultures did not was listed in Bergey’s Manual (16) as the type comply with the type description and, in fact, were species and was described as possessing peritri- found to be gram-positive rods. Moreover, both chous cells; A. liquidurn was described as possess- the original and subsequent descriptions of ing polar flagella. Documentation of the specific A c hromo bacter liq uefaciens we re so i nde te rm i- reasons for ascribing peritrichous cells to A. nate and apparently were not based on the liquefaciens is lacking. examination of extant cultures that they attracted As described in Bergey’s Manual (16), orga- a heterogeneous collection of what are now ob- nisms of the genus Alcaligenes differed from those viously widely divergent strains. On these grounds, of Achrornobacter in that the former were of the Judicial Commission is asked to issue an intestinal origin and did not ferment carbohy- Opinion rejecting the generic name Achromobac- drates. The description of Achromobacter did not ter as a nomen dubium. mention the action on carbohydrates but stated Emended description of Alcaligenes faecalis Cas- that the organisms were from soil and water. Both tellani and Chalmers (1919) (41). The following genera included nonmotile and motile forms, al- revised description of Alcaligenes faecalis is based though no polarly flagellated cells were described upon an investigation of available strains, includ- in Alcaligenes. Clearly, even in this early publica- ing the reference strain ATCC 8750 (= NCIB tion, grounds for separation of the genera were 8 156). questionable. Succeeding editions of Bergey’s Coccoid rods, 0.5 to 0.6 by 2.0 pm, usually Manual emphasized the action on carbohydrates occurring singly. Motile by means of one to eight and, for Alcaligenes, in the 7th edition it was flagella. Cells are peritrichous. Gram negative. No specifically stated that carbohydrates were not special pigments are produced. A characteristic attacked. The action of Achromobacter strawberry-like odor is produced by some strains. liquefaciens on carbohydrates has not been re- Acetate, propionate, butyrate, and other organic ported. As a result of the description presented in acids are utilized as sole carbon and energy Bergey’s Manual (16), the genus Achromobacter sources, as are aspartic acid, asparagine, histidine, was used to place a very heterogeneous collection glutathione, and some other organic nitrogenous of organisms reputed to be aerobic, gram-negative, compounds. The utilization of carbohydrates and motile or nonmotile bacteria occurring in soils, chemolithotrophic growth using H2gas have not water, foods, etc. been demonstrated. Oxidation of arsenite, which is The most recent descriptions of the genera very active in some strains, does not support Alcaligenes (25) and Achrornobacter (26) are as chemolithotrophic growth. follows. Sole nitrogen sources include ammonium and 536