Summary auto-generated
This study describes the taxonomic characterization of five bacterial strains isolated from Antarctic coastal environments. The bacteria were psychrotrophic, aerobic, gram-negative rods with polar flagella and G+C contents of 41-42 mol%. Through comprehensive phenotypic, genetic, and chemotaxonomic analyses, including DNA-DNA hybridization, 16S rRNA sequencing, fatty acid analysis, and protein profiling, the researchers determined these strains constituted a new species within the genus Pseudoalteromonas. The Antarctic isolates were distinct from previously described Pseudoalteromonas species, particularly P. haloplanktis and P. atlantica, though they shared 99% 16S rRNA sequence similarity with P. haloplanktis. All strains required only 17 mM Na+ for growth, considerably less than other Pseudoalteromonas species. The strains formed a homogeneous genomic group with DNA-DNA similarities of 80% or greater among themselves but only 20-22% similarity to P. haloplanktis type strain, supporting classification as a separate species. The authors propose the name Pseudoalteromonas antarctica sp. nov. for these organisms, with strain NF3T designated as the type strain.
Key findings
- Five bacterial strains from Antarctic coastal environments represent a new Pseudoalteromonas species, distinguished from related species by phenotypic characteristics, DNA-DNA hybridization values of 20-22% with P. haloplanktis (threshold for new species), and G+C content of 41-42 mol%
- The Antarctic isolates require only 17 mM Na+ for growth, substantially lower than other Pseudoalteromonas species which require 125-600 mM Na+
- 16S rRNA sequence analysis placed the new species on the Pseudoalteromonas phylogenetic branch with 99% sequence similarity to P. haloplanktis subsp. haloplanktis, yet DNA-DNA hybridization results clearly established it as a distinct species
- The five Antarctic strains formed a homogeneous genomic group with internal DNA-DNA similarity greater than 80%, confirmed by identical SDS-PAGE protein profiles and similar fatty acid compositions
- Pseudoalteromonas antarctica sp. nov. is psychrotrophic with growth range of 4-30°C, strictly aerobic, and cannot utilize DL-malate, D-sorbitol, or m-hydroxybenzoate as sole carbon sources
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Abstract
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 haloplanktis and Pseudoalteromonas atlantica, 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 EN10 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.