Comparative genomic analyses of four novel Ramlibacter species and the cellulose-degrading properties of Ramlibacter cellulosilyticus sp. nov.

Abstract

AbstractIn this study, four novel bacterial strains, USB13T, AW1T, GTP1T, and HM2T, were isolated from various environments in Busan and Jeju Island, Republic of Korea. The 16S rRNA sequencing results indicated that the four novel strains belong to the genusRamlibacter.All four strains were tested for their potential cellulolytic properties, where strain USB13Twas identified as the only novel bacterium and the first within its genus to show cellulolytic activity. When tested, the highest activities of endoglucanase, exoglucanase,β-glucosidase, and filter paper cellulase (FPCase) were 1.91 IU/mL, 1.77 IU/mL, 0.76 IU/mL, and 1.12 IU/mL, respectively at pH 6.0. Comparisons of draft whole genome sequences (WGS) were also made using average nucleotide identity, digital DNA-DNA hybridization values, and average amino acid identity values, while whole genome comparison was visualized using the BLAST Ring Image Generator. The G + C contents of the strains ranged from 67.9 to 69.9%, while genome sizes ranged from 4.31 to 6.15 Mbp. Based on polyphasic evidence, the novel strains represent four new species within the genusRamlibacter, for which the namesRamlibacter cellulosilyticussp. nov. (type strain, USB13T = KACC 21656T = NBRC 114839T)Ramlibacter aurantiacussp. nov. (type strain, AW1T = KACC 21544T = NBRC 114862T),Ramlibacter albussp. nov. (type strain, GTP1T = KACC 21702T = NBRC 114488T), andRamlibacter pallidussp. nov. (type strain, HM2T = KCTC 82557T = NBRC 114489T) are proposed.