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

Abstract

Two separate bacterial strains, PMTSA4T 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 PMTSA4T and PMR2A8 are closely related to Flavobacterium piscinae ICH-30T (95.6%, respectively), Flavobacterium ahnfeltiae 10Alg 130T (95.5%) and Flavobacterium maris KMM 9535T (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 4008T (dDDH: 19.8% and ANI: 75.5%), F. piscinae ICH-30T (dDDH: 18.6% and ANI: 73.3%) and F. stagni WWJ 16T (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-C15:0, iso-C17:0 3-OH and iso-C15:0 3-OH. Menaquinone-6 was the predominant quinone. Considering the results from phenotypic, chemotaxonomic, phylogenetic and genomic analyses, it is proposed that the strains PMTSA4T and PMR2A8 represent a novel species within the genus Flavobacterium.