Halobacteriovorax vibrionivorans sp. nov., a novel prokaryotic predator isolated from coastal seawater of China

Three prokaryotic predator strains, BL9T, BL10 and BL28, were isolated with Vibrio alginolyticus from coastal seawater of PR China. Cells of the strains were Gram-negative, vibrioid-shaped and motile with a single sheathed flagellum (25–28 nm wide). Cells were around 0.3×0.5–1.0 µm in size. The three strains were obligate predators that exhibited a biphasic life cycle: a free-swimming attack phase and an intraperiplasmic growth phase within the prey. Bdelloplasts were formed. NaCl was required for growth. Optimum growth occurred at ~37 °C, with 2–4 % (w/v) NaCl and at pH 7.0–8.0. The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that the three strains shared 99.9 % similarity to each other, were affiliated with the genus Halobacteriovorax in the class Oligoflexia, and represented the same new species. Strain BL9T (=MCCC 1K03527T=JCM 32962T) was designated as the type strain. Genome sequencing of strain BL9T revealed a genome size of 3.14 Mb and a G+C content of 35.8 mol%. The estimated digital DNA–DNA hybridization (dDDH) values and the whole genome average nucleotide identity (gANI) values between the genome of strain BL9T and those of Bdellovibrionales and Bacteriovoracales were 12.5–19 and 63.49–76.15 %, respectively. On the basis of life cycle features, results of physiological analyses, gANI data and dDDH data, strain BL9T represents a new species within the genus Halobacteriovorax , for which the name Halobacteriovorax vibrionivorans sp. nov. is proposed.