Three novel bacterial species isolated from plasma-treated soil: Hymenobacter plasmatis sp. nov., Flavitalea plasmicola sp. nov. and Mucilaginibacter tolerans sp. nov.

Abstract

Cold atmospheric plasma (CAP) is a potent antimicrobial technology; however, the taxonomic diversity of soil bacteria capable of withstanding direct plasma exposure remains poorly understood. In this study, three novel bacterial strains, designated BT770^T, BT771^T and BT774^T, were isolated from CAP-treated soil. Cells of all strains were Gram-stain-negative, non-motile and rod-shaped. In direct plasma exposure assays, all three strains exhibited enhanced survival compared with Escherichia coli K-12, with strain BT774^T showing particularly high tolerance. Phylogenetic analysis based on 16S rRNA gene sequences and phylogenomic reconstruction placed strains BT770^T, BT771^T and BT774^T within the genera Hymenobacter, Flavitalea and Mucilaginibacter, respectively. The closest relatives were Hymenobacter sedentarius DG5B^T (97.98%), Flavitalea antarctica AQ6—291 ^T (96.70%) and Mucilaginibacter frigoritolerans F22^T (95.60%). Draft genome sizes ranged from 5.1 to 8.7 Mb, and DNA G + C content ranged from 42.3 to 60.6%. Genomic relatedness indices, including average nucleotide identity (ANI) and digital DNA–DNA hybridisation (dDDH), between the isolates and their closest relatives were below the accepted species delineation thresholds (95–96% ANI and 70% dDDH), supporting their classification as novel species. This conclusion was further supported by chemotaxonomic and phenotypic characteristics. Based on a polyphasic taxonomic approach, strains BT770^T, BT771^T and BT774^T are considered to represent three novel species within the phylum Bacteroidota, for which the names Hymenobacter plasmatis sp. nov. (BT770^T = KACC 22526 ^T = NBRC 116070 ^T), Flavitalea plasmicola sp. nov. (BT771^T = KACC 22527 ^T = NBRC 116071 ^T) and Mucilaginibacter tolerans sp. nov. (BT774^T = KACC 22530 ^T = NBRC 116072 ^T) are proposed, respectively.