RESUMO
Bacterial diversity in sub-Antarctic seawater, collected off Ushuaia, Argentina, was examined using a culture independent approach. The composition of the 16S rRNA gene libraries from seawater and seawater contaminated with the water soluble fraction of crude oil was statistically different (P value 0.001). In both libraries, clones representing the Alphaproteobacteria, Gammaproteobacteria, the Cytophaga-Flavobacterium-Bacteroidetes group and unculturable bacteria were dominant. Clones associated with the genera Roseobacter, Sulfitobacter, Staleya, Glaciecola, Colwellia, Marinomonas, Cytophaga and Cellulophaga were common to both the libraries. However, clones associated with Psychrobacter, Arcobacter, Formosa algae, Polaribacter, Ulvibacter and Tenacibaculum were found only in seawater contaminated with hydrocarbons (Table 1). Further, the percentage of clones of Roseobacter, Sulfitobacter and Glaceicola was high in seawater (43%, 90% and 12% respectively) compared to seawater contaminated with hydrocarbons (35%, 4% and 9% respectively). One of the clones F2C63 showed 100% similarity with Marinomonas ushuaiensis a bacterium identified by us from the same site.
Assuntos
Alteromonadaceae/isolamento & purificação , Psychrobacter/isolamento & purificação , Rhodobacteraceae/isolamento & purificação , Roseobacter/isolamento & purificação , Água do Mar/microbiologia , Alteromonadaceae/classificação , Alteromonadaceae/genética , Regiões Antárticas , Argentina , DNA Bacteriano/análise , DNA Bacteriano/isolamento & purificação , DNA Ribossômico/análise , Biblioteca Gênica , Hidrocarbonetos , Dados de Sequência Molecular , Filogenia , Psychrobacter/classificação , Psychrobacter/genética , RNA Ribossômico 16S/genética , Rhodobacteraceae/classificação , Rhodobacteraceae/genética , Roseobacter/classificação , Roseobacter/genética , Água do Mar/química , Análise de Sequência de DNA , Poluição Química da ÁguaRESUMO
A Gram-negative, rod-shaped, psychrophilic, motile, non-spore-forming bacterium, strain U1T, was isolated from Ushuaia located at the southernmost tip of Argentina. On the basis of 16S rRNA gene sequence similarity, strain U1T was found to be closely related to Marinomonas communis (DSM 5604T) and Marinomonas primoryensis (IAM 15010T). At the DNA-DNA level, however, the values for similarity were 41 and 25 %, respectively. The major fatty acids present were iso-C(16 : 0), C(16 : 1)omega7c, iso-C(17 : 1) and C(18 : 1)omega7c and the G+C content of the DNA was 43.6 mol%. All of the above characteristics support the affiliation of strain U1T to the genus Marinomonas. Furthermore, on the basis of phenotypic features, chemotaxonomic characteristics and phylogenetic analysis of the 16S rRNA gene sequence, it appears that strain U1T is distinct from the four Marinomonas species with validly published names. Strain U1T, therefore, represents a novel species, for which the name Marinomonas ushuaiensis sp. nov. is proposed. The type strain of M. ushuaiensis is U1T (=MTCC 6143T=DSM 15871T=JCM 12170T).