Pseudomonas deceptionensis sp. nov., a psychrotolerant bacterium from the Antarctic.

During the taxonomic investigation of cold-adapted bacteria from samples collected in the Antarctic area of the South Shetland Islands, one Gram-reaction-negative, psychrotolerant, aerobic bacterium, designated strain M1(T), was isolated from marine sediment collected on Deception Island. The organism was rod-shaped, catalase- and oxidase-positive and motile by means of a polar flagellum. This psychrotolerant strain grew at temperatures ranging from -4 °C to 34 °C. Phylogenetic studies based on 16S rRNA gene sequences confirmed that Antarctic isolate M1(T) was a member of the genus Pseudomonas and was located in the Pseudomonas fragi cluster. 16S rRNA gene sequence similarity values were >98 % between 13 type strains belonging to the Pseudomonas fluorescens lineage. However, phylogenetic analysis of rpoD gene sequences showed that strain M1(T) exhibited high sequence similarity only with respect to Pseudomonas psycrophila (97.42 %) and P. fragi (96.40 %) and DNA-DNA hybridization experiments between the Antarctic isolate M1(T) and the type strains of these two closely related species revealed relatedness values of 58 and 57 %, respectively. Several phenotypic characteristics, together with the results of polar lipid and cellular fatty acid analyses, were used to differentiate strain M1(T) from related pseudomonads. Based on the evidence of this polyphasic taxonomic study, strain M1(T) represents a novel species, for which the name Pseudomonas deceptionensis sp. nov. is proposed. The type strain is M1(T) ( = LMG 25555(T)  = CECT 7677(T)).

Shewanella vesiculosa sp. nov., a psychrotolerant bacterium isolated from an Antarctic coastal area.

Two strains of psychrotolerant bacteria, designated M7(T) and M5, isolated from Antarctic coastal marine environments were studied to determine their taxonomic position. The organisms comprised Gram-negative, rod-shaped, facultatively anaerobic cells that were motile by means of single polar flagella. Neither of the bacterial isolates had a requirement for Na(+). These two psychrotolerant strains grew at temperatures ranging from -4 to 30 degrees C. Both strains were capable of producing H(2)S from thiosulfate and were able to use sodium nitrate and trimethylamine N-oxide as terminal electron acceptors during anaerobic growth. 16S rRNA gene sequence analysis placed M7(T) and M5 within the genus Shewanella; the strains showed the highest similarity (99.9 and 99.2 % respectively) with respect to the type strains of Shewanella livingstonensis and Shewanella frigidimarina. However the levels of gyrB sequence similarity between strain M7(T) and the type strains of S. livingstonensis and S. frigidimarina were 87.6 and 87.4 %, respectively. DNA-DNA hybridization experiments performed between the Antarctic isolate M7(T) and S. livingstonensis LMG 19866(T) and S. frigidimarina LMG 19475(T) revealed levels of relatedness of 32 and 35 %, respectively. Strain M5 showed 100 % DNA relatedness with respect to strain M7(T). The DNA G+C content of these bacteria was 42 mol%. Several phenotypic characteristics, the cellular fatty acid compositions and the quinone content of strains M7(T) and M5 served to differentiate them from related shewanellae. On the basis of the data from this polyphasic taxonomic study, M7(T) and M5 constitute a single genospecies. They represent a novel species of the genus Shewanella, for which the name Shewanella vesiculosa sp. nov. is proposed. The type strain is M7(T) (=LMG 24424(T) =CECT 7339(T)).

Marinobacter guineae sp. nov., a novel moderately halophilic bacterium from an Antarctic environment.

Two Gram-negative, cold-adapted, moderately halophilic, aerobic bacteria, designated strains M3B(T) and M3T, were isolated from marine sediment collected from the South Shetland Islands, Antarctica. The organisms were rod-shaped, catalase- and oxidase-positive, and motile by means of polar flagella. These two psychrotolerant strains required Na(+) and grew at NaCl concentrations of 1-15 % and temperatures between 4 and 42 degrees C. 16S rRNA gene sequence analysis placed strains M3B(T) and M3T within the genus Marinobacter. DNA-DNA hybridization experiments between the Antarctic isolate M3B(T) and type strains of phylogenetically related species, namely Marinobacter lipolyticus, Marinobacter flavimaris, Marinobacter sediminum, Marinobacter algicola, Marinobacter maritimus and Marinobacter koreensis, revealed levels of relatedness lower than 32 %. Strain M3T showed 99 % DNA relatedness to strain M3B(T). The DNA G+C contents of M3B(T) and M3T were 57.1 and 57.4 mol%, respectively, and their major isoprenoid quinone was ubiquinone-9. Several phenotypic characteristics, together with data on cellular fatty acid composition, served to differentiate strains M3B(T) and M3T from strains of related Marinobacter species. On the basis of the polyphasic taxonomic evidence presented in this study, it can be concluded that strains M3B(T) and M3T belong to the same genospecies and represent a novel species of the genus Marinobacter, for which the name Marinobacter guineae sp. nov. is proposed. The type strain is M3B(T) (=LMG 24048(T)=CECT 7243(T)).