Phylogenomic insights into distribution and adaptation of Bdellovibrionota in marine waters
Bdellovibrionota is composed of obligate predators that can consume some gram-negative bacteria inhabiting various environments. However, whether genomic traits influence their distribution and marine adaptation remains to be answered. In this study, we performed phylogenomics and comparative genomics studies on 82 Bdellovibrionota genomes along with five metagenome-assembled genomes (MAGs) from deep sea zones. Four phylogenetic groups, Oligoflexia, Bdello-group1, Bdello-group2 and Bacteriovoracia, were revealed by constructing a phylogenetic tree, of which 53.84% of Bdello-group2 and 48.94% of Bacteriovoracia were derived from ocean. Bacteriovoracia was more prevalent in deep sea zones, whereas Bdello-group2 was largely distributed in the epipelagic zone. Metabolic reconstruction indicated that genes involved in chemotaxis, flagellar (mobility), type II secretion system, ABC transporters and penicillin-binding protein were necessary for predatory lifestyle of Bdellovibrionota. Genes involved in glycerol metabolism, hydrogen peroxide (H2O2) degradation, cell wall recycling and peptide utilization were ubiquitously present in Bdellovibrionota genomes. Comparative genomics between marine and non-marine Bdellovibrionota demonstrated that betaine as an osmoprotectant is probably widely used by marine Bdellovibrionota, meanwhile, all the marine genomes have a number of related genes for adapting marine environment. The chitinase and chitin-binding protein encoding genes were identified for the first time in Oligoflexia, which implied that Oligoflexia may prey a wider spectrum of microbes. This study expanded our knowledge on adaption strategies of Bdellovibrionota inhabiting deep sea and their potential usage for biological control. ImportanceBdellovibrionota can prey gram-negative bacteria proposed as biocontrol agent. Available Bdellovibrionota genomes showed that most are from marine environment. However, vertical distribution and adaption of Bdellovibrionota in deep sea has not been reported. Our study of Bdellovibrionota revealed four groups (Oligoflexia, Bdello-group1, Bdello-group2 and Bacteriovoracia) and their distribution pattern in oceans. We also identified the genes for different phases of predation and adaptation in deep-sea environment. Moreover, Oligoflexia genomes contain more genes for carbohydrates utilization and particularly those encoding chitin-binding protein and chitinase. Our analyses of Bdellovibrionota genomes may help understand their special lifestyle and deep-sea adaptation.