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

Abstract

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 ° C, between pH 6 and pH 9 and tolerated up to 11·5% NaCl. The cell wall peptidoglycan was Lys-Thr-Ala3 (the A3α variant) and the major menaquinone was MK-9(H₂). 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 ° 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).