This study describes Halomonas subglaciescola, a new halotolerant bacterial species isolated from Organic Lake, a hypersaline meromictic lake in Antarctica. Twenty-nine bacterial strains were collected from various depths and analyzed using numerical taxonomic procedures, testing 92 different attributes. The new isolates shared key characteristics of the genus Halomonas, including DNA guanine-plus-cytosine content of 60.9–62.9 mol%, salt tolerance, primarily oxidative metabolism, motility when present, and peritrichous flagellation. However, they did not cluster with reference strains including Halomonas elongata. Distinguishing features of H. subglaciescola include cytochrome oxidase positivity, inability to grow at 37°C, and failure to utilize glucose and other sugars for growth. The species comprises two biovars: biovar I contains motile, potentially filamentous strains (represented by type strain ACAM 12), while biovar II contains nonmotile strains (represented by strain ACAM 21). All strains grew optimally in media with 2.5–20% NaCl, tolerated pH 5–9, and grew at 0–25°C. Most strains utilized amino acids and organic acids but not sugars as carbon sources.

Key findings

• Halomonas subglaciescola sp. nov., a new halotolerant bacterial species, was isolated from an Antarctic hypersaline lake using 29 strains and identified through numerical taxonomic analysis of 92 attributes
• The species is distinguished from the related H. elongata by cytochrome oxidase positivity, inability to grow at 37°C, and inability to utilize glucose and other sugars for growth
• H. subglaciescola comprises two biovars: biovar I (motile, filamentous, type strain ACAM 12) and biovar II (nonmotile, strain ACAM 21), with DNA G+C content ranging from 60.9–62.9 mol%
• Strains grew optimally at 2.5–20% NaCl and 0–25°C, with preference for amino acids and organic acids over sugars as carbon sources, reflecting adaptation to their Antarctic saline lake environment