Summary auto-generated
Researchers isolated a novel halophilic archaeon, strain CM5T, from a crude sea-salt sample collected near Qingdao, China. The organism is a Gram-negative, non-motile coccus that forms red-pigmented colonies and grows optimally at 35-40°C and pH 6.0 in 20% NaCl. Phylogenetic analysis of 16S rRNA gene sequences showed closest relationships to Halococcus species, with 99.3% similarity to Halococcus morrhuae. However, strain CM5T exhibits distinctive characteristics: it does not produce hydrogen sulfide or liquefy gelatin, can utilize glucose as a sole carbon source, and has a lower optimal salt concentration (18-20%) compared to related species. DNA-DNA reassociation values with reference Halococcus strains ranged from 29.6% to 57.1%, all below the 70% threshold for species delineation. The polar lipid profile and antibiotic susceptibility pattern are consistent with the genus Halococcus. Based on morphological features, chemotaxonomic properties, phylogenetic analysis, and genetic data, the authors propose strain CM5T as the type strain of a novel species, Halococcus qingdaonensis sp. nov.
Key findings
- Halococcus qingdaonensis is a new halophilic archaeal species isolated from sea salt, characterized by coccoid morphology, red pigmentation, and growth at 18-20% optimal NaCl concentration
- The organism differs from related Halococcus species by lacking H2S production and gelatin liquefaction, not producing organic acids from sugars, and showing reduced antibiotic susceptibility to several compounds
- 16S rRNA gene sequence analysis shows 99.3% similarity to H. morrhuae but DNA-DNA reassociation values of 29.6-57.1% with reference strains confirm designation as a distinct species
- Polar lipid composition includes phosphatidylglycerol, phosphatidylglycerol methylphosphate, and sulfated diglycosyl diether, consistent with the Halococcus genus, with G+C content of 61.2 mol%
- The strain CM5T (type strain) grows optimally at 35-40°C and pH 6.0, requires minimum 10% NaCl, and can utilize glucose as sole carbon source for growth
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Abstract
A Gram-negative, extremely halophilic, coccoid archaeal strain, CM5T, was isolated from a crude sea-salt sample collected near Qingdao, China. The organism grew optimally at 3540 °C and pH 6.0 in the presence of 20 % (w/v) NaCl. Its colonies were red in colour and it could use glucose as a sole carbon source for growth. The 16S rRNA gene sequence of CM5T was most closely related to those of Halococcus species. Its pattern of antibiotic susceptibility was similar to those of other described Halococcus species. Biochemical tests revealed no sign of H2S production or gelatin liquefaction. The main polar lipids of strain CM5T were phosphatidylglycerol, phosphatidylglycerol methylphosphate and sulfated diglycosyl diether. No phosphatidylglycerol sulfate was present. The DNA G+C content of strain CM5T was 61.2 mol% and it gave DNADNA reassociation values of 33.7, 57.1 and 29.6 %, respectively, with Halococcus salifodinae DSM 8989T, Halococcus dombrowskii DSM 14522T and Halococcus morrhuae ATCC 17082T. Based on its morphological and chemotaxonomic properties and phylogenetic analysis of 16S rRNA gene sequence data, we propose that CM5T should be classified within a novel species, Halococcus qingdaonensis sp. nov., with strain CM5T (=CGMCC 1.4243T=JCM 13587T) as the type strain.