CHARACTERIZING AND EXTENDING THE OLIGOFLEXIA CLASS OF PREDATORY BACTERIA THROUGH LARGE-SCALE GENOME-RESOLVED METAGENOMICS

Predatory bacteria are best characterized within the Bdellovibrionales and Bacteriovoracels orders. These have been recently reassigned from the Deltaproteobacteria class to the new Oligoflexia class within the Proteobacteria phylum. Bdellovibrio bacteriovorous and Halobacteriovorax marinus are well-studied type strains that typify the two orders. Bdellovibrionales were known to occur in terrestrial and freshwater environments while Bacteriovoracels occur in marine environments. Taxonomic and metabolic characterization of environmental members of these orders and of the class Oligoflexia, in general, is still very partial. Here we analyzed >110 non-redundant Oligoflexia genomes, most of which recovered from metagenomics samples, to better characterize this class. Twelve of the analyzed genomes were newly recovered in this study from the Tara Oceans expedition dataset. All genome were carefully compared in-depth using specific protein and rRNA genes and using a novel synteny-base measure by whole proteomes. Overall, the analyzed genomes represent novelty at the species and genus levels. The class can be divided into four major groups. The groups encompassing the Bdellovibrionales and Bacteriovoracels orders each include both freshwater and marine bacteria. The marine bacteria are abundant across the world oceans and over a wide range of depths between the surface to 800 m below sea level. Marine Bdellovibrionales are aerobic, have quorum sensing and biofilm formation genes and also genes related to predation such as adhesins, carboxypeptidases, and hemolysins. Nevertheless, Oligoflexia includes two characterized non-predatory bacteria. Our results provide new information on the abundance, taxonomy and metabolic capabilities of Oligoflexia bacteria; characterize many environmental members, and offer new insights on the evolution predatory bacteria.