Flavobacterium litorale sp. nov., isolated from red alga

Abstract

A Gram-stain-negative and rod-shaped bacterial strain (WSW3-B6^T) was isolated from red alga collected from the West Sea, Republic of Korea. Cells of strain WSW3-B6^T were non-motile, aerobic and produced slightly yellow and mucoid colonies on marine agar. The strain grew optimally at 23-30 °C, with 0.5-4 % NaCl (w/v) and at pH 6.5-8.5. A phylogenetic analysis of the 16S rRNA gene revealed that strain WSW3-B6^T belongs to the genus Flavobacterium within the family Flavobacteriaceae, having the highest sequence similarity to Flavobacterium arcticum SM1502^T (96.7%), followed by Flavobacterium salilacus subsp. altitudinum LaA7.5^T (96.2%) and Flavobacterium salilacus subsp. salilacus SaA2.12^T (96.2%). The complete sequence of a circular chromosome of strain WSW3-B6^T determined by combination of Oxford Nanopore and Illumina platforms comprised a total 2 725 095 bp with G+C content of 37.1 mol%. A comparative analysis based on the whole genome also showed the distinctiveness of strain WSW3-B6^T. The average nucleotide identity (ANI) values between strain WSW3-B6^T and the closest strains F. arcticum SM1502^T, F. salilacus subsp. altitudinum LaA7.5^T and F. salilacus subsp. salilacus SaA2.12^T were 78.3, 77.8 and 77.7 %, respectively, while the digital DNA-DNA hybridization (dDDH) values between strain WSW3-B6^T and the above closely related strains were 21.0, 20.4 and 20.3 %, respectively. Both the ANI and dDDH values supported the creation of a new species in the genus Flavobacterium. The major fatty acids (>10 %) were iso-C_{15 : 0} (19.3 %), C_{16 : 0} (14.0 %), iso-C_{17 : 0} 3-OH (13.1 %) and C_{18 : 0} (10.7 %). The polar lipids of strain WSW3-B6^T included phosphatidylethanolamine, three unidentified aminolipids and three unidentified lipids. Moreover, MK-6 was the only respiratory quinone. A comparison of the phylogenetic distinctiveness and the unique phenotypic and chemotaxonomic characteristics among strain WSW3-B6^T and closely related type strains supported that strain WSW3-B6^T (=KCTC 82708^T=GDMCC 1.2627^T) represents a novel species of the genus Flavobacterium, for which the name Flavobacterium litorale sp. nov. is proposed.

Keywords: Bacteroidota; bacteria; seaweed.