Pseudoxanthomonas fibrivorans sp. nov. 10H^T, a cellulose-degrading bacterium isolated from soil

A Gram-stain-negative, rod-shaped, flagellated and motile bacterium, designated 10H^T was isolated from soil sample collected in Guangxi Province, China. This strain displays activities including catalase, urease, and activities related to Tween 20, 40, and 80. Optimal growth occurs at 33 °C, without NaCl and pH 7-8. The major quinone component is ubiquinone-8 (Q-8). The polar lipids mainly composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unknown amino lipid, and four unknown lipids. The major fatty acids were iso C_15:0, anteiso C_15:0 and Summed Feature 9 (iso C_17:1ω9c). The complete genome sequence was 3.56 Mbp in length with a G + C content of 71.27%. Strain 10H^T showed less than 98.73% 16S rRNA gene sequence similarity with type strains of the genus Pseudoxanthomonas. Phylogenetic analysis based on 16S rRNA gene, core genes, and genome-wide data indicated that the strain belongs to the genus Pseudoxanthomonas. Furthermore, the results showed that strain 10H^T established a unique and distinguishable lineage in conjunction with Pseudoxanthomonas kaohsiungensis J36^T. The average nucleotide identity (ANI) values between 10H^T and the closest Pseudoxanthomonas strains were 76.98%-85.95%, and the digital DNA‒DNA hybridization (dDDH) values were between 18.90% and 30.50%. Additionally, strain 10H^T demonstrated the ability to grow in a medium with sodium carboxymethyl cellulose as the sole carbon source, Whole-genome sequencing identified multiple genes associated with cellulose degradation, and experimental assays confirmed cellulase activity reaching up to 350 U/L. Based on these findings, we propose the novel species Pseudoxanthomonas fibrivorans sp. nov., with strain 10H^T (= CCTCC AB2024091^T = KCTC 8654 ^T) as the type strain, which demonstrates clear cellulose-degrading capabilities.