Arthrobacter flavus sp. nov., a psychrophilic bacterium isolated from a pond in McMurdo Dry Valleys, Antarctica

CMS 19Y(T), a psychrophilic bacterium, was isolated from a cyanobacterial mat sample from a pond in Antarctica and was characterized taxonomically. The bacterium was aerobic, Gram-positive, non-spore-forming, non-motile, exhibited a rod--coccus growth cycle and produced a yellow pigment that was insoluble in water but soluble in methanol. No growth factors were required and it was able to grow between 5 and 30 degrees C, between pH 6 and pH 9 and tolerated up to 11.5% NaCl. The cell wall peptidoglycan was Lys-Thr-Ala3 (the A3alpha variant) and the major menaquinone was MK-9 (H(2)). The G+C content of the DNA was 64 +/- 2 mol%. The 16S rDNA analysis indicated that CMS 19Y(T) is closely related to group I Arthrobacter species and showed highest sequence similarity (97.91%) with Arthrobacter agilis. Furthermore, DNA--DNA hybridization studies also indicated 77% homology between CMS 19Y(T) and A. agilis. It differed from A. agilis, however, in that it was psychrophilic, non-motile, yellow in colour, exhibited a rod--coccus growth cycle, had a higher degree of tolerance to NaCl and was oxidase- and urease-negative and lipase-positive. In addition, it had a distinct fatty acid composition compared to that of A. agilis: the predominant fatty acids were C(15:0), anteiso-C(15:0), C(16:0), iso-C(16:0), C(17:0), anteiso-C(17:0) and C(18:0). It is proposed, therefore, that CMS 19Y(T) should be placed in the genus Arthrobacter as a new species, i.e. Arthrobacter flavus sp. nov. The type strain of A. flavus is CMS 19Y(T)(=MTCC 3476(T)).