Flavobacterium capsici sp. nov., isolated from the rhizospheric soils of bell pepper (Capsicum annuum L.).

Abstract

Two separate bacterial strains, PMTSA4^T and PMR2A8, were isolated from the rhizospheric soils of bell pepper plants grown in a plant nursery. These strains are Gram-negative, non-motile and rod-shaped and grow in aerobic conditions. They exhibit a positive reaction for catalase activity but negative results for oxidase activity. Phylogenetic analysis of the 16S rRNA gene sequences revealed that the strains PMTSA4^T and PMR2A8 are closely related to Flavobacterium piscinae ICH-30^T (95.6%, respectively), Flavobacterium ahnfeltiae 10Alg 130^T (95.5%) and Flavobacterium maris KMM 9535^T (95.3%), aligning them within the genus Flavobacterium. Digital DNA-DNA hybridization (dDDH) values and average nucleotide identities (ANIs) of the whole-genome sequences for the two strains and related Flavobacterium species were significantly below the established thresholds for prokaryotic species delineation (<70% for dDDH and <95% for ANI). The observed values were as follows: Flavobacterium aquatile LMG 4008^T (dDDH: 19.8% and ANI: 75.5%), F. piscinae ICH-30^T (dDDH: 18.6% and ANI: 73.3%) and F. stagni WWJ 16^T (dDDH: 18.5% and ANI: 72.0%). The strains have genome sizes of 3 068 185 bp and 3 068 330 bp, with a G+C content of 32.5 mol%. In phenotypic characterization, the new strains grew at 10-35 °C and tolerated up to 4% NaCl at pH 5-9 (optimum pH 8). The predominant cellular fatty acids were observed to be iso-C_15:0, iso-C_17:0 3-OH and iso-C_15:0 3-OH. Menaquinone-6 was the predominant quinone. Considering the results from phenotypic, chemotaxonomic, phylogenetic and genomic analyses, it is proposed that the strains PMTSA4^T and PMR2A8 represent a novel species within the genus Flavobacterium.