Isolation and characterization of Lacibacter aquaticus sp. nov. and Lacibacter koreensis sp. nov., isolated from lake water

Two novel Gram-stain-negative, aerobic, motile by gliding, bacterial strains, designated H375^T and H407^T, were isolated from freshwater in South Korea. To determine their taxonomic positions, the strains were fully characterized. Based on information, including 16S rRNA gene and draft genome sequences, both isolates (H375^T and H407^T) were found to belong to the genus <i>Lacibacter</i>. H375^T shares the highest 16S rRNA gene similarity (99.2%) with <i>Lacibacter sediminis</i> S13-6-22^T. In addition, H407^T also shows (98.3%) 16S rRNA gene similarity with <i>L. sediminis</i> S13-6-22^T. The draft genomes of strains H375^T and H407^T consisted of 5,079,137 and 4,865,722 bp, respectively, and had DNA G+C contents of 40.0 mol% and 40.7 mol%. The average nucleotide identity between H375^T and H407^T was 81.7%, and the digital DNA-DNA hybridization value was 24.5%, both below the species delineation threshold. Strains H375^T and H407^T possessed menaquinone-7 as the predominant respiratory quinone and their fatty acid profiles included C_15:0 iso, C_15:0 iso 3OH, C_15:1 iso G, C_17:0 iso 3OH and C_16:1 ω7c/C_16:1 ω6c (summed feature 3) as the major fatty acids, supporting their affiliation to the genus <i>Lacibacter</i>. The major known polar lipid in both novel isolates was phosphatidylethanolamine. Moreover, physiological and biochemical results allowed the phenotypic and genotypic differentiation of strains H375^T and H407^T from their closest and other species of the genus <i>Lacibacter</i> with validly published names. Therefore, H375^T and H407^T represented novel species of the genus <i>Lacibacter</i>, for which the names <i>Lacibacter aquaticus</i> sp. nov. (type strain H375^T=KACC 23521^T=LMG 33421^T) and <i>Lacibacter koreensis</i> sp. nov. (type strain H407^T=KACC 23522^T=LMG 33422^T) were proposed.