Biochemical and phylogenetic analyses of psychrophilic isolates belonging to the Arthrobacter subgroup and description of Arthrobacter psychrolactophilus, sp nov.

During our work on psychrophilic microorganisms we obtained a large collect ion of new isolates. In order to identify six of these, we examined their g rowth properties, cell wall compositions, and their 16S rRNA gene sequences . The results showed that all of the isolates are gram-positive, aerobic, c ontain lysine in their cell walls, and belong to the high mol% G+C Arthroba cter subgroup. Phylogenetic analysis of the 16S rRNA genes grouped five iso lates obtained from a small geographical region into a monophyletic clade. Isolate B7 had a 16S rRNA sequence that was 94.3% similar to that of Arthro bacter polychromogenes and 94.4% similar to that of Arthrobacter oxydans. P rimary characteristics that distinguish isolate B7 from the Arthrobacter ty pe strain (Arthrobacter globiformis) and A. polychromogenes include lack of growth at 37 degrees C, growth at 0-5 degrees C, the ability to use lactos e as a sole carbon source, and the absence of blue pigments. Because of the se differences, isolate B7 was chosen as a type strain representing a new A rthrobacter species, Arthrobacter psychrolactophilus. The sixth isolate, LV 7, differed from the other five because it did not have the rod/coccus morp hological cycle and was most closely related to Arthrobacter agilis.