Halosimplex yunnanense sp. nov., a novel haloarchaeon from an underground salt mine

Strain J119^T, a halophilic archaeon, was isolated from a salt mine sample collected in Yunnan Province, China. Cells are spherical (diameter 0.5-0.7 µm) or short‑rod‑shaped (0.4-0.5 × 0.7-0.8 µm), non‑motile, Gram‑stain‑negative, and can grow at 20-55°C (optimum 42°C), with NaCl tolerance ranging from 15% to 30% (w/v) (optimum 20%) and a pH growth range of 5.5-9.0 (optimum pH 7.0). Strain J119^T's nearly complete 16S rRNA gene sequence (1,452 bp; accession MW736888.1) shows the highest sequence similarity (97.32%) to Halosimplex salinum YPL4^T; this value is lower than the species boundary threshold of 98.65%. Its rpoB' gene (1,830 bp; NZ_JBTJEL000000000.1) shares the highest similarity (95.52%) with Halosimplex aquaticum XZYJT29^T. Genomic analyses revealed that the average amino acid identity, average nucleotide identity and digital DNA-DNA hybridization values between strain J119^T and strains YPL4^T and XZYJT29^T were 78.58%, 82.59%, 25.50% and 82.61%, 85.70%, 29.20%, respectively. The genomic DNA G + C content of strain J119^T is 66.5%. Phenotypic, phylogenetic, and genome-based analyses suggest that strain J119^T (= KCTC 4326^T = MCCC 4K00178^T) represents a novel species of the genus Halosimplex, for which the name Halosimplex yunnanense sp. nov. is proposed.