Aquabacterium lacunae sp. nov., isolated from a freshwater pond.

A novel bacterial strain, designated KMB7T, isolated from a freshwater pond in Taiwan, was characterized using a polyphasic taxonomic approach. Cells were Gram-stain-negative, motile by means of a single polar flagellum, rod-shaped and formed cream colonies. Optimal growth occurred at 25 °C, pH 7, and in the absence of NaCl. Phylogenetic analyses based on 16S rRNA gene sequences and an up-to-date bacterial core gene set (92 protein clusters) indicated that strain KMB7T is affiliated with species in the genus Aquabacterium. The 16S rRNA gene sequence similarity indicated that strain KMB7T is closely related to species within the genus Aquabacterium (95.2-97.6 % sequence similarity) and is most similar to A. fontiphilum CS-6T (97.6 %), followed by A. parvum B6T (97.5 %). The average nucleotide identity and digital DNA-DNA hybridization identity between strain KMB7T and the closely related strains were 74.6-78.0 % and 19.0-21.2 %, respectively. The major fatty acids of strain KMB7T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C18 : 1 ω7c and C16 : 0. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, diphosphatidylglycerol and four unidentified phospholipids. The sole isoprenoid quinone was ubiquinone-8 (Q-8). Genomic DNA G+C content of strain KMB7T was 65.4 %. On the basis of phenotypic and genotypic properties and phylogenetic inference, strain KMB7T should be classified in a novel species of the genus Aquabacterium, for which the name Aquabacterium lacunae sp. nov. is proposed. The type strain is KMB7T (=BCRC 81156T=LMG 30924T=KCTC 62867T).