sp. nov., sp. nov. and sp. nov., three novel chitin-degrading actinobacteria isolated from a mudflat sediment.

Three strains of actinobacteria, designated as SYSU T00194, SYSU T00242 and SYSU T00266, were isolated from tidal flat sediment samples in Zhanjiang, PR China. The taxonomic position of three isolates was determined using polyphasic taxonomic analysis and phylogenomic analysis. Phylogenetic analysis and 16S rRNA gene sequence comparisons indicated that strain SYSU T00194 formed a distinct clade with IFO 16236 and shared a sequence identity value of 97.9%. As well as strains SYSU T00242 and SYSU T00266, which formed a distinct clade with CGMCC 4.1717, exhibiting sequence identity values of 97.7 and 97.6%, respectively. Furthermore, they also exhibited a closer phylogenetic relationship with IFO 16235, as determined by phylogenomic analysis, with average nucleotide identity values of 86.1 and 91.1%, respectively. These novel isolates could be distinguished from species in the genus by their distinct phenotypic and genotypic characteristics. The cells of three novel strains were aerobic, Gram-stain-positive and short rod-shaped. Optimal growth conditions of strains SYSU T00194, SYSU T00242 and SYSU T00266 occurred on the marine agar 2216 with pH 8.0 at 37 °C. In addition, the major fatty acids of SYSU T00194, SYSU T00242 and SYSU T00266 were iso-C, anteiso-C and anteiso-C. The major polar lipids included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and glycolipid (GL). According to the phenotypic, genotypic and phylogenetic data, strains SYSU T00194, SYSU T00242 and SYSU T00266 represent three novel species of the genus , for which the names sp. nov., sp. nov. and sp. nov. are proposed, respectively. The type strains of the proposed three novel isolates are SYSU T00194 (=MCCC 1K09402=KCTC 59364), SYSU T00242 (=GDMCC 1.3836=KCTC 44948) and SYSU T00266 (=GDMCC 1.3835=KCTC 49949), respectively.