Summary auto-generated
This study describes the characterization and taxonomic classification of two novel haloalkaliphilic archaeal strains, C231T and C42, isolated from Chahannao soda lake in Inner Mongolia, China. Both strains are rod-shaped, Gram-negative archaea that form bright red colonies. They require high salt concentrations (optimum 3.5 M NaCl) and alkaline pH (optimum 8.5) for growth, with cell lysis occurring in dilute solutions below 1.5 M NaCl. The organisms are chemo-organotrophs capable of both aerobic and anaerobic growth using nitrate, DMSO, or trimethylamine N-oxide as electron acceptors. They utilize alanine, ornithine, and pyruvate as carbon sources and reduce nitrate to nitrite. Phylogenetic analysis based on 16S rDNA sequences placed the strains within the Natronobacterium genus, clustering with Natronobacterium gregoryi and Natronococcus species with 91% bootstrap support. DNA-DNA hybridization revealed 99-100% relatedness between C231T and C42 but only 12% or less relatedness to other Natronobacterium and Natronorubrum species. Lipid composition analysis showed characteristic archaeal ether lipids with diphytanyl and phytanyl-sesterterpanyl moieties, absent glycolipids, and 63.8 mol% GC content. Based on these combined molecular, morphological, and biochemical characteristics, the authors propose Natronobacterium nitratireducens sp. nov., with C231T designated as the type strain.
Key findings
- Two novel haloalkaliphilic archaeal strains isolated from Chinese soda lake requiring 2.5-3.5 M NaCl and pH 8.0-10.5 for growth
- Strains capable of anaerobic respiration using nitrate, DMSO, and TMAO; nitrate reduction distinguishes them from known Natronobacterium gregoryi
- 16S rDNA phylogenetic analysis placed strains in Natronobacterium genus with 96% sequence similarity to N. gregoryi but low DNA-DNA hybridization (<12%), confirming species-level distinction
- Characteristic archaeal lipid composition lacking glycolipids but containing phosphatidylglycerol and phosphatidylglycerophosphate methyl ester with C20:C20 and C20:C25 diether cores
- Proposal of Natronobacterium nitratireducens sp. nov. with type strain C231T based on combined molecular and phenotypic evidence
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Abstract
Two novel haloalkaliphilic archaea, strains C231(T) and C42, were isolated from a soda lake in China. Cells of the two strains were rod-shaped and Gram-negative and colonies were bright red. They required at least 2.5 M NaCl for growth, with an optimum at 3.5 M NaCl, and grew over a pH range from 8.0 to 10.5, with an optimum at pH 8.5. Hypotonic treatment with less than 1.5 M NaCl caused cell lysis. They had similar polar lipid compositions, possessing the diphytanyl (C20:C20) and phytanyl-sesterterpanyl (C20:C25) diether derivatives of phosphatidylglycerol and phosphatidylglycerophosphate methyl ester and a minor phospholipid, PL1. No glycolipids were detected. Comparison of 16S rDNA sequences and morphological features placed them in the genus Natronobacterium. Detailed phenotypic characterization and DNA--DNA hybridization studies revealed that the two strains belong to a new species in the genus Natronobacterium, for which the name Natronobacterium nitratireducens sp. nov. is proposed. The type strain is C231(T) (=AS 1.1980(T) =JCM 10879(T)).