Genome-Based Classification of Pedobacter albus sp. nov. and Pedobacter flavus sp. nov. Isolated from Soil

Abstract

Two rod-shaped, non-spore-forming, Gram-negative bacteria, strain KR3-3T isolated from fresh soil in Korea and strain VNH31T obtained from soil samples from motorbike repair workshop floors in Vietnam, were identified. Phylogenetic analysis utilizing 16S rRNA gene sequences revealed their affiliation with the family Sphingobacteriaceae and their relation to the genus Pedobacter, exhibiting 16S rRNA gene sequence similarities lower than 98.00% with all known species within the genus Pedobacter. Growth of VNH31T and KR3-3T was impeded by NaCl concentrations exceeding >0.5% and 1.5%, respectively, while they both thrived optimally at temperatures ranging between 25 and 30 °C. Notably, neither strain reduced nitrate to nitrite nor produced indole. Negative results were observed for the acidification of D-glucose and hydrolysis of urea, gelatin, casein, and starch. VNH31T exhibited growth on β-galactosidase, sodium acetate, L-serine, and L-proline, whereas KR 3-3T demonstrated growth on D-glucose, D-mannose, D-maltose, N-acetyl-glucosamine, sucrose, sodium acetate, L-serine, 4-Hydroxybenzoic acid, and L-proline. Core genome-based phylogenetic analysis revealed that the two isolates formed distinct clusters within the genus Pedobacter. The DNA G+C contents of KR3-3T and VNH31T were determined to be 44.12 mol% and 32.96 mol%, respectively. The average nucleotide identity and in silico DNA-DNA hybridization relatedness values (67.19–74.19% and 17.6–23.6%, respectively) between the Pedobacter isolates and the closely related type strains fell below the threshold values utilized for species delineation. Following comprehensive genomic, chemotaxonomic, phenotypic, and phylogenetic analyses, the isolated strains are proposed as two novel species within the genus Pedobacter, named Pedobacter albus sp. nov. (type strain KR3-3T = KACC 23486T = NBRC 116682T) and Pedobacter flavus sp. nov. (type strain VNH31T = KACC 23297T = CCTCC AB 2023109T).