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A Gram-negative, mobile, rod-shaped, non-spore-forming bacterium (strain 14-3T) was isolated from a temporary pond in Antarctica. On the basis of 16S rRNA gene sequence similarity, strain 14-3T was shown to belong to the genus Pseudomonas sensu stricto. Physiological and biochemical tests supported the phylogenetic affiliation. Strain 14-3T is closely related to Pseudomonas veronii DSM 11331T, sharing 99.7% sequence similarity. DNA–DNA hybridization experiments between the two strains showed only moderate reassociation similarity (35.1%). Tests for arginine dihydrolase and nitrate reduction were positive, while those for denitrification, indol production, glucose acidification, urease, ß-galactosidase, esculin, caseine and gelatin hydrolysis were negative. Growth of this bacterium occurred in a range from 4 to 37°C but not at 42°C. It accumulated poly(3-hydroxybutyrate) when grown on sodium octanoate medium. Strain 14-3T therefore represents the type strain of a new species, for which the name Pseudomonas extremaustralis sp. nov. is proposed. The type strain 14-3T has been deposited as DSM 17835T and as CIP 109839T. [ABSTRACT FROM AUTHOR]

Abstract: Pseudomonas sp. 14-3 is an Antarctic bacterium that shows high stress resistance in association with high polyhydroxybutyrate (PHB) production. In this paper genes involved in PHB biosynthesis (phaRBAC) were found within a genomic island named pha-GI. Numerous mobile elements or proteins associated with them, such as an integrase, insertion sequences, a bacterial group II intron, a complete Type I protein secretion system and IncP plasmid-related proteins were detected among the 28 ORFs identified in this large genetic element (32.3kb). The G+C distribution was not homogeneous, likely reflecting a mosaic structure that contains regions from diverse origins. pha-GI has strong similarities with genomic islands found in diverse Proteobacteria, including Burkholderiales species and Azotobacter vinelandii. The G+C content, phylogeny inference and codon usage analysis showed that the phaBAC cluster itself has a complex mosaic structure and indicated that the phaB and phaC genes were acquired by horizontal transfer, probably derived from Burkholderiales. These results describe for the first time a pha cluster located within a genomic island, and suggest that horizontal transfer of pha genes is a mechanism of adaptability to stress conditions such as those found in the extreme Antarctic environment. [Copyright &y& Elsevier]