Arch Microbiol (1999) 171:355–363 © Springer-Verlag 1999 ORIGINAL PAPER Jennifer Loveland-Curtze · Peter P. Sheridan · Kevin R. Gutshall · Jean E. Brenchley Biochemical and phylogenetic analyses of psychrophilic isolates belonging to the Arthrobacter subgroup and description of Arthrobacter psychrolactophilus, sp. nov. Received: 17 December 1998 / Accepted: 12 March 1999 Abstract During our work on psychrophilic microorgan- their cold-active enzymes, particularly β-galactosidases. isms we obtained a large collection of new isolates. In or- During this work we have isolated numerous organisms der to identify six of these, we examined their growth pro- from geographically distant habitats ranging from Penn- perties, cell wall compositions, and their 16S rRNA gene sylvania farmlands to Antarctica. Many of these psy- sequences. The results showed that all of the isolates are chrophiles are gram-positive, non-spore-forming rods. gram-positive, aerobic, contain lysine in their cell walls, Four isolates (B7, D2, D5, and D10) were physiologically and belong to the high mol% G+C Arthrobacter subgroup. characterized and assigned to the genus Arthrobacter be- Phylogenetic analysis of the 16S rRNA genes grouped cause they are strict aerobes, have rod/coccus morpholog- five isolates obtained from a small geographical region ical cycles, and contain lysine in their cell walls (Love- into a monophyletic clade. Isolate B7 had a 16S rRNA se- land et al. 1994; DePrada et al. 1996). quence that was 94.3% similar to that of Arthrobacter Arthrobacter species are members of the high mol% polychromogenes and 94.4% similar to that of Arthro- G+C actinomycete-coryneform bacteria (Stackebrandt bacter oxydans. Primary characteristics that distinguish and Woese 1981; Jones and Collins 1986; Jones and Ked- isolate B7 from the Arthrobacter type strain (Arthrobacter die 1992). Criteria for distinguishing closely related gen- globiformis) and A. polychromogenes include lack of era has traditionally relied on morphological characteris- growth at 37°C, growth at 0–5°C, the ability to use lactose tics such as a rod/coccus cycle and the composition of the as a sole carbon source, and the absence of blue pigments. cell wall peptidoglycan, especially the identity of the di- Because of these differences, isolate B7 was chosen as a amino acid. This grouping, however, contains a diverse type strain representing a new Arthrobacter species, Arthro- collection of bacterial taxa, not all of which form irregular bacter psychrolactophilus. The sixth isolate, LV7, dif- rods or contain the same diamino acid in their cell walls fered from the other five because it did not have the rod/ (Jones and Collins 1986). In addition, reliance on chemo- coccus morphological cycle and was most closely related taxonomic characteristics yields little insight into the evo- to Arthrobacter agilis. lutionary relationships among these organisms. Previous work, primarily by Stackebrandt and his colleagues, has Key words Arthrobacter psychrolactophilus · catalogued and compared the 16S rRNA sequences of Psychrophilic · Cell wall · Rod/coccus morphology · several members of the high mol% G+C gram-positive or- 16S rRNA phylogeny ganisms (Stackebrandt and Fiedler 1979; Koch et al. 1994, 1995; Rainey et al. 1994; Stackebrandt et al. 1995). The results of these extensive studies demonstrate that Introduction phylogenetic intermixing of genera can arise and illustrate the difficulty of using chemotaxonomic features alone for Research in our laboratory has focused on the isolation of identification (Rainey et al. 1994; Koch et al. 1995; psychrophilic microorganisms and the characterization of Stackebrandt et al. 1995). The heterogeneity of the different coryneform bacteria is also illustrated by the comparison of the 16S rRNA se- J. Loveland-Curtze · P. P. Sheridan · K. R. Gutshall · quences in the Ribosomal Database Project (RDP; (Maidak J. E. Brenchley (౧) et al. 1994). Sequences from most of the aerobic and some Department of Biochemistry and Molecular Biology, of the facultative coryneform taxa cluster in a collection The Pennsylvania State University, 209 South Frear, designated by the RDP as the Arthrobacter group, which University Park, PA 16802, USA e-mail: [email protected], encompasses the Microbacterium subgroup, the Clavibac- Tel.: +1-814-8637794, Fax: +1-814-8653330 ter assemblage, the Arthrobacter subgroup, and the Der- 356 Table 1 Comparison of the amino acid composition in cell walls of the isolates B7, D5, D2, D10, RG1, LV7, and Arthrobacter Materials and methods globiformis. The values for A. globiformis are an average of four amino acid determinations, and the total picomol were 33,381. The Isolation and cultivation values for the isolates B7, D5, and D2 are averages of two amino aacid determinations. The total picomol were 21,079 for isolate Isolates B7, D2, D5, and D10 were obtained from soil samples B7, 31,697 for isolate D5, and 33,519 for isolate D2. The total pi- from whey-enriched farm fields (Loveland et al. 1994; DePrada et comol were 24,168 for isolate D10, 41,663 for isolate RG1, and al. 1996), and strain RG1 was obtained from a limestone quarry. 25,636 for isolate LV7. Minor amounts of other amino acids are Isolate LV7 was obtained from a cyanobacterial mat sample from not reported a lake (designated “Lake Vestal”) located near the Miers and Adams glaciers in Antarctica. Portions of frozen mat were inocu- Amino acid composition (% of total picomol) lated into Instant Ocean medium [1% peptone, 0.2% lactose, and 75% strength seawater, which was reconstituted from Instant Isolate LYS DAPORN ALA THR SER GLYGLU LEU Ocean salts (Aquarium Systems, Mentor, Ohio, USA)] and incu- bated at 5°C. Cells growing in this enrichment were purified by re- A. globi- 13.4 0.5 0.1 44.0 2.3 2.9 5.1 11.0 5.0 streaking on Instant Ocean agar [1% peptone, 0.2% lactose, 75% formis strength seawater, which was reconstituted from Instant Ocean B7 14.8 1.4 0.07 50.0 5.1 3.7 4.1 10.7 2.5 salts (Aquarium Systems), and 1.5% agar] and incubated at 5°C. D5 13.3 1.4 0.01 50.1 5.6 4.0 4.0 10.4 2.5 The A. globiformis ATCC 8010 type strain was obtained from L. D2 13.9 1.8 0.06 46.4 6.0 3.8 4.7 10.8 3.1 E. Casida, Jr., (Pennsylvania State University). D10 11.8 0.0 0.0 42.9 11.2 2.4 4.0 10.8 4.4 Trypticase soy broth (TSB) and trypticase soy agar (TSA) with no added carbohydrate were used for determining cell morphology RG1 12.9 0.0 0.0 38.8 10.7 2.6 4.1 11.4 4.6 and for determining the temperature ranges for growth, except for LV7 9.2 0.0 0.0 40.6 8.8 2.2 6.0 10.6 4.8 the isolate obtained from Lake Vestal. Isolate LV7 was grown in either 75% or 100% seawater medium prepared using Instant Ocean salts. BactoPeptone (1%; Difco, Detroit, Mich., USA) and 0.2% lactose or glucose were added to the seawater medium. matophilus subgroup. Traditional genus designations lie For determining carbohydrate utilization and vitamin require- within these groups. For example, the Arthrobacter sub- ments, isolates were grown in M9 medium (Miller 1972) contain- group includes the genera Arthrobacter, Brevibacterium, ing 0.2% carbohydrate and/or 1 ml Medium Eagle Vitamin Solu- tion (Gibco BRL, Gaithersburg, Md., USA) per 100 ml. To check Micrococcus, Renibacterium, and Rothia. The major tax- for utilization of nicotine and production of pigment, isolate B7 onomic properties distinguishing these genera have been was cultured on nicotine agar composed of 0.4% nicotine, 0.2% cell shape, the presence or absence of a rod/coccus mor- KH2HPO4, 0.5% KCl, 0.01% yeast extract, 0.0025% MgSO4, phological cycle, and the presence of either lysine or meso- 0.0025% FeSO4, 1.5% agar, and tap water, with the pH adjusted to 6.8. Isolate B7 was grown on peptone-yeast agar (1% peptone, 2% diaminopimelic acid as the predominant diamino acid in glycerol, 0.6% KCl, and 2% agar) to determine production of the the cell wall (Table 1). blue pigments characteristic of A. polychromogenes. Considering the difficulty of accurately placing organ- isms in the Arthrobacter subgroup into appropriate gen- era, we undertook the current study to identify our iso- Enzyme determinations lates. The first goal was to further characterize our psy- General enzyme production was determined using API Coryne test chrophilic isolates B7, D2, D5, and D10 by determining strips (Bio-Merieux Vitek, Hazelwood, Mo., USA). Gelatin hy- whether their phylogenetic placement was consistent with drolysis was detected by inoculating cells onto nutrient agar con- the previous physiological data. Second, we wanted to de- taining 5% gelatin and, after growth, by flooding the agar with sat- termine and compare the properties of two new isolates, urated ammonium sulfate to highlight the zones of hydrolysis. RG1 and LV7. Third, we examined whether the diamino acids present in the cell walls of our isolates corresponded Cell wall characterization with their phylogenetic placement and if our findings would clarify whether features such as presence of a Cell wall extracts were prepared according to the short method de- scribed by Schleifer and Kandler (1972). The extracts were then rod/coccus cycle and lysine in the cell wall are useful for hydrolyzed completely, and quantitative amino acid analyses were identifying members of the Arthrobacter subgroup. And done at The Hershey Medical Center of the Pennsylvania State fourth, we addressed the question of whether the isolates University or at The University of Michigan Protein and Carbohy- were similar to previously characterized organisms or if drate Structure Facility. they represented new and distinct species by comparing their chemotaxonomic and phylogenetic placements with Scanning electron microscopy those previously examined.