Thirty-one bacteria that belonged to the genus Pseudomonas were isolated from cyanobacterial mat samples that were collected from various water bodies in Antarctica. All 31 isolates were psychrophilic; they could be divided into three groups, based on their protein profiles. Representative strains of each of the three groups, namely CMS 35T, CMS 38T and CMS 64T, were studied in detail. Based on 16S rRNA gene sequence analysis, it was established that the strains were related closely to the Pseudomonas fluorescens group. Phenotypic and chemotaxonomic characteristics further confirmed their affiliation to this group. The three strains could also be differentiated from each other and the closely related species Pseudomonas orientalis, Pseudomonas brenneri and Pseudomonas migulae, based on phenotypic and chemotaxonomic characteristics and the level of DNA–DNA hybridization. Therefore, it is proposed that strains CMS 35T (=MTCC 4992T=DSM 15318T), CMS 38T (=MTCC 4993T=DSM 15319T) and CMS 64T (=MTCC 4994T=DSM 15321T) should be assigned to novel species of the genus Pseudomonas as Pseudomonas antarctica sp. nov., Pseudomonas meridiana sp. nov. and Pseudomonas proteolytica sp. nov., respectively.

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CMS 19YT , 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 SC, between pH 6 and pH 9 and tolerated up to 115 % NaCl. The cell wall peptidoglycan was Lys-Thr-Ala3 (the A3α variant) and the major menaquinone was MK-9(H 2 ). The GMC content of the DNA was 64O2 mol %. The 16S rDNA analysis indicated that CMS 19YT is closely related to group I Arthrobacter species and showed highest sequence similarity (9791 %) 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, nonmotile, yellow in colour, exhibited a rod-coccus growth cycle, had a higher degree of tolerance to NaCl and was oxidase-and urease-negative and lipasepositive. In addition, it had a distinct fatty acid composition compared to that of A. agilis : the predominant fatty acids were C

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Twelve strains of psychrophilic bacteria were isolated from cyanobacterial mat samples collected from various water bodies in the McMurdo Dry Valley region of Antarctica. All the isolates were Gram-negative, non-motile, coccoid, psychrophilic, halotolerant bacteria and had C16 : 1 ω7c, C17 : 1 ω8c and C18 : 1 ω9c as the major fatty acids, ubiquinone-8 as the respiratory quinone and DNA G+C content of 41–46 mol%. Based on these characteristics, the isolates were assigned to the genus Psychrobacter. Based on their SDS-PAGE profiles, the 12 isolates could be categorized into three groups. Six isolates of Group I were identified as representing strains of Psychrobacter okhotskensis. However, using detailed phenotypic and chemotaxonomic characteristics and phylogenetic analysis based on their 16S rRNA gene sequences, strain CMS 39T, the only strain from Group II, and strain CMS 56T, a representative strain of Group III, were different from each other and from all recognized species of Psychrobacter. Therefore, it is proposed to classify CMS 39T (=DSM 15337T=MTCC 4208T) and CMS 56T (=DSM 15339T=MTCC 4386T) as representing the type strains of novel species of Psychrobacter, for which the names Psychrobacter vallis sp. nov. and Psychrobacter aquaticus sp. nov., respectively, are proposed.

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Strain CMS 90rT, a red-pigmented bacterium, was isolated from a cyanobacterial mat sample from a pond located in McMurdo, Antarctica. Based on its chemotaxonomic and phylogenetic properties, strain CMS 90r(T) was identified as a member of group I of Arthrobacter. It shared 16S rDNA similarity of 98% with Arthrobacter oxydans ATCC 14358T and Arthrobacter polychromogenes ATCC 15216T, while DNA-DNA similarities determined for these three organisms were less than 70%. It also differed from all 17 reported Arthrobacter species with A3alpha-variant peptidoglycan in that it possessed a unique peptidoglycan (Lys-Gly-Ala3) and contained galactose, glucose, ribose and rhamnose as cell-wall sugars. These data and the presence of diagnostic phenotypic traits support the description of CMS 90r(T) as a novel species of Arthrobacter, for which the name Arthrobacter roseus sp. nov. is proposed. The type strain is strain CMS 90r(T) (= MTCC 3712T = DSM 14508T).