Virgibacillus saliphilus sp. nov. and Virgibacillus salidurans sp. nov., isolated from kimchi.

Abstract

This study aimed to provide a taxonomic description of two bacterial strains, NKC19-3T and NKC19-16T, isolated from commercially produced kimchi obtained from various regions within the Republic of Korea. Both strains were rod-shaped, gram-stain-positive, facultatively anaerobic, and displayed positive reactions for oxidase and catalase. Additionally, these bacteria were motile, halophilic (salt-tolerant), and proliferated under alkaline conditions. Genetically, both strains showed 98.0% similarity in their 16S rRNA gene sequences and were most closely related to Virgibacillus natechei FarDT, with 96.5 and 96.8% sequence similarity, respectively. ANI values indicated that the two novel strains were distinct from V. natechei FarDT, as they were below the species demarcation threshold. The ANI value between strains NKC19-3ᵀ and NKC19-16ᵀ was 84.64-84.75%, and the values between these strains and other related strains did not exceed 80.0%, further supporting their classification as novel species. Phylogenetic analysis revealed that strains NKC19-3T and NKC19-16T formed a distinct branch within the genus Virgibacillus, clearly distinguishing them from other species in the same genus. Regarding genomic characteristics, the GC content was 38.9% for strain NKC19-3T and 39.5% for strain NKC19-16T. The genome of strain NKC19-3T had a size of approximately 4.1 Mb and contained 3,785 protein-coding genes (CDSs). Strain NKC19-16T had a slightly smaller genome, approximately 3.9 Mb in size and harbored 3,726 CDSs. The polar lipid profiles of strains NKC19-3ᵀ and NKC19-16ᵀ included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), glycolipids (GL), and an unidentified lipid (L). The predominant fatty acids of both strains were anteiso-C15:0 and anteiso-C17:0. Considering the comprehensive analysis encompassing phenotypic, genomic, phylogenetic, and chemotaxonomic data, strains NKC19-3T and NKC19-16T are proposed to represent two novel species within the genus Virgibacillus. The suggested names for these species are Virgibacillus saliphilus sp. nov. (type strain NKC19-3T, also referred to as KACC 22326T and DSM 112707T) and Virgibacillus salidurans sp. nov. (type strain NKC19-16T, also referred to as KACC 22327T and DSM 112708T).