Sphingobium trunci sp. nov. and Peribacillus folii sp. nov.: two novel phosphate- and zinc-solubilizing bacteria isolated from Kaempferia marginata Carey in Thailand

Two endophytic bacterial strains, designated as Sx8-8ᵀ and SI8-4ᵀ, were isolated from the stem and leaf tissues, respectively, of Kaempferia marginata Carey collected in Thailand. A comprehensive taxonomic investigation employing a polyphasic approach was conducted to characterize these strains. Strain Sx8-8ᵀ is a Gram-negative, aerobic, rod-shaped, non-spore-forming bacterium that produces yellow pigment on Reasoner’s 2A agar (R2A) medium. Phylogenetic analysis based on 16S rRNA gene sequences placed this strain within the genus Sphingobium , showing the highest similarity (98.5%) to Sphingobium chungbukense KACC 12347ᵀ (=DJ77 T ). The draft genome was 4.7 Mb in size with a G+C content of 64 mol%. Genome-wide comparisons with closely related type strains yielded an average nucleotide identity based on blastn (ANIb) and MUMmer (ANIm) values of 82.2–84.0% and 86.7–86.9%, respectively, with digital DNA–DNA hybridization (dDDH) values of 28.4–29.1%. Chemotaxonomic data supported its affiliation to the genus, with Q-10 identified as the major respiratory quinone, along with characteristic fatty acid and polar lipid profiles. These findings support the proposal of a novel species, Sphingobium trunci sp. nov., with Sx8-8ᵀ (=LMG 33805ᵀ=TBRC 17746ᵀ) as the type strain. Strain SI8-4ᵀ is a Gram-positive, aerobic, spore-forming, rod-shaped bacterium, producing pale pink pigment on R2A medium. It was identified as a member of the genus Peribacillus , sharing the highest 16S rRNA gene sequence similarity (99.0%) with Peribacillus frigoritolerans JCM 11681ᵀ and Peribacillus muralis DSM 16288ᵀ. The genome was 4.6 Mb in size, with a G+C content of 43 mol%. Comparative genomic analyses revealed ANIb and ANIm values of 80.0–86.0% and 84.3–87.8%, respectively, while dDDH values were 24.3–32.1%. The major quinone was MK-7, and the fatty acid and polar lipid compositions were consistent with members of the genus Peribacillus . Based on genotypic and phenotypic distinctiveness, strain SI8-4ᵀ is proposed to represent a novel species, Peribacillus folii sp. nov. The type strain is SI8-4ᵀ (=KACC 23903ᵀ=KCTC 43756ᵀ=TBRC 17747ᵀ)