Abstract
Two Gram-stain negative, facultative anaerobic, oxidase-negative, catalase-positive bacilli, designated as strains TMQ4T and TMQ2, were isolated from Xiaoshi Island, China, using prey-traps. Growth was observed within the ranges 25-45°C (optimally at 37°C), pH 6.5-9.0 (optimally at pH 7.5-8.0) and 1-8% NaCl (optimally at 3-4%, w/v). The draft genome sequences of strains TMQ4T and TMQ2 contained 184 contigs of 5,609,735bp with a G+C content of 64.4% and 148 contigs of 5,589,985bp with a G+C content of 65.0%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that both strains belonged to the genus Lujinxingia with the similarity of 98.9%. The phylogenetic and phylogenomic topologies and analyses demonstrated that both strains clustered together and differentiated from the closest neighbour, Lujinxingia sediminis SEH01T. Genomic analyses showed that two strains lost the biosynthesis pathway of several chemical compounds. Iso-C15:0 was contained in the predominant cellular fatty acids in both strains. The major polar lipids of both strains consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and unidentified lipids; and the respiratory quinone was menaquinone MK-7 for both strains. Both strains predated other bacteria, including Owenweeksia hongkongensis JCM 12287T and Paraliobacillus ryukyuensis DSM 15140T, and were lured with one prey Acinetobacter baumannii ATCC 19606T in prey-trap. Combining genomic analyses, two strains had the predatory indices of 2, similar to representative typical bacterial predators. The physiological, biochemical, and phylogenetic properties suggest that the two strains represent a novel species within the genus Lujinxingia. The name Lujinxingia vulgaris sp. nov. is proposed, with strain TMQ4T (= KCTC 62851T = MCCC 1H00392T) as type strain and strain TMQ2 (= KCTC 72,079 = MCCC 1H00381) as reference strain.
Highlights
The order Bradymonadales was established by Wang et al at 2015 with a single representative Bradymonas sediminis FA350T (Wang et al 2015)
Phylogenetic analysis based on 16S rRNA gene sequences showed two strains belonged to the genus Lujinxingia, and their closest neighbour was Lujinxingia sediminis SEH01T, both with the similarity of 98.9 %
We introduce a novel species of the genus Lujinxingia, with predatory characteristics, which indicating further extension of this bacterial group
Summary
The order Bradymonadales was established by Wang et al at 2015 with a single representative Bradymonas sediminis FA350T (Wang et al 2015). The following year, Persicimonas caeni YN101T was proposed as the representative of the genus Persicimonas, which yields an unusual big genome (compared with other members in the order Bradymonadales) of 8,047,206 bp in length (Wang et al 2020). Multiple nutritional deficiencies in cells of bradymonabacteria made them relying on prey cells to a certain degree. Though these predators could live without prey cells, the existence of prey allowed bradymonabacteria a better growth. Bradymonabacteria was suggested as facultatively prey-dependent predators for all its predatory features (Mu et al 2020), which may allow it a unique ecological niche in marine environment
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