Three strains of psychrophilic bacteria isolated from Antarctic coastal marine environments were studied to determine their taxonomic position. These bacteria were Gram-negative rods, facultatively anaerobic and motile by means of a single polar flagellum. None of the bacterial isolates had an Na M requirement. Only one of the strains was capable of producing H 2 S from thiosulfate. The DNA base content of these bacteria was 41-42 mol % GMC. DNA-DNA hybridization experiments showed that the isolates formed two related groups that exhibited about 70 and 24 % DNA-DNA homology, respectively, with the type strain of Shewanella frigidimarina. The fatty acid profiles of the bacterial isolates were similar to the profiles of other Shewanella species. All the strains contained both ubiquinones and menaquinones, like Shewanella species. Methylmenaquinones were also found. 16S rRNA gene analysis confirmed that isolated strains belonged to the genus Shewanella and were phylogenetically related to the newly identified Shewanella frigidimarina. The results of the polyphasic taxonomic study assigned the three isolates to Shewanella and two of them specifically to Shewanella frigidimarina. INTRODUCTIONThe genus Shewanella was first described 14 years ago by MacDonell & Colwell (1985). The definition of Shewanella was based almost entirely on rRNA structure and included only the description ' straight or curved rods, Gram-negative, non-pigmented, motile by polar flagella, chemo-organotrophic, oxidasepositive, generally associated with aquatic or marine habitats. GjC mol % 44-47 '. The species Shewanella putrefaciens (Derby & Hammer, 1931 ; Lee et al., 1977) and Shewanella hanedai (Jensen et al., 1980) Abbreviation : TMAO, trimethylamine N-oxide.The EMBL accession numbers for the 16S rDNA gene sequence of strains NF12 and NF22 T are AJ300833 and AJ300834, respectively. included in the genus Shewanella, nine of which have been described in the last 3 years. Although the development of this bacterial group, from a taxonomic point of view, has taken place in the last decade, Shewanella putrefaciens has been studied since its first description as Achromobacter putrefaciens by Derby & Hammer (1931), because of its special interest in the areas of applied and environmental microbiology.Shewanella putrefaciens, first isolated as Achromobacter putrefaciens from rancid butter, was classified in 1960 as Pseudomonas putrefaciens by Shewan et al. (1960) and, later, as Alteromonas putrefaciens by Lee et al. (1977). This micro-organism has been found to be associated with the spoilage of proteinaceous foods (Shewan, 1977). Shewanella species are widely distributed and have been isolated from diverse sources such as aquatic environments (Nealson et al., 1991), sediments (Myers & Nealson, 1988), oilfield fluids Nu! ria Bozal and others (Semple & Westlake, 1987) and, as mentioned above, spoilage of proteinaceous foods (Levin, 1972 ;Shewan, 1974 ;Parker & Levin, 1983 ;Stenstrom & Molin, 1990), and are considered opportunistic pathogens...
An endospore-forming strain, 20CM T , was isolated from Antarctic sediment and identified as a member of the genus Paenibacillus on the basis of phenotypic and phylogenetic analyses.
The taxonomic characteristics of five bacterial strains which were isolated from Antarctic coastal marine environments were studied. These bacteria were psychrotrophic, aerobic, and gram negative with polar flagella. The G+C contents of the DNAs of these strains were 41 to 42 mol%. The Antarctic strains were phenotypically distinct from the previously described Pseudoalteromonas type species. DNA-DNA hybridization experiments revealed that the new strains were closely related to each other but clearly different from Pseudoalteromonas halophnktis and Pseudoalteromonas athntica, which were the most phenotypically similar organisms. None of the bacterial isolates was capable of using DL-malate, D-sorbitol, or m-hydroxybenzoate, and all were capable of gelatin hydrolysis. Strains NF2, NF3T (T = type strain), NF13, NF14, and ENlO had an Na+ requirement but required only 17 mM Na+. Phenotypic, DNA G+C content, DNA-DNA hybridization, 16s rRNA analysis, fatty acid composition, and protein profile data confirmed the identification of the Antarctic strains as members of a Pseudoalteromonas sp. The name Pseudoalteromonas antarctica sp. nov. is proposed for these organisms.The genus Pseudoalteromonas (15), originally called Alteromonas, included nonpigmented, gram-negative, heterotrophic, aerobic, polarly flagellated species of marine bacteria which had G+C contents ranging from 38 to 50 mol%, which differentiated this bacterial group from the previously described genus Pseudomonas (4, 5, 7, 20 (2,6,9,12,(16)(17)(18)(19)22,25,28,30,41,48), although a recent revision of genera based on phylogenetic analysis by Gauthier et al. (15) divided the genus Alteromonas into two genera, the genera Pseudoalteromonas and Alteromonas. Separation of Pseudoalteromonas species on the basis of phenotypic characteristics is problematic because of significant variations in phenotypic traits (23) and because phenotypic differences have frequently been observed even among genetically closely related strains (1). Thus, in order to determine the relationships between Pseudoalteromonas species, genetic and chemotaxonomic methods appear to provide more reliable information than differential phenotypic characteristics.The aim of this work was to describe a taxonomic study of some aerobic heterotrophic bacteria isolated from samples collected in the South Shetland Islands (Antarctica) by a Spanish scientific expedition during the Antarctic summer of 1987 and 1988. Part of the microbiota was composed of motile nonpigmented rods. Five of these bacterial strains, strains NF2, NF3T (T = type strain), NF13, NF14, and EN10, belong to the genus Pseudoalteromonas. In this study, morphological, phenotypic, genetic, and chemotaxonomic analyses were performed to clarify the taxonomic position of these bacterial isolates. Our results show that this bacterial group from an Antarctic environment constitute a new species of the recently proposed genus Pseudoalteromonas. MATERIALS AND METHODSBacterial strains and isolation. Strains NF2, NF3T, NF12, NF13, and NF14 w...
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