Bdellovibrio: Lone Hunter “Cousin” of the “Pack Hunting” Myxobacteria

Abstract

This chapter describes about the isolation of Bdellovibrio and myxobacteria from similar soil environments, and the employment of an arsenal of hydrolytic enzymes to kill and digest other bacteria to provide for their own growth and division. It concentrates on the ecology and motility systems of Bdellovibrio, followed by an overview of the hydrolytic enzymes used in prey digestion. It is clear that the nonobligately symbiotic or parasitic, predatory bacteria like Bdellovibrio and Myxobacteria have large genomes akin to those of heterotrophs; thus, determining whether transfer of predatory gene islands is responsible for apparently quite diverse bacteria adapting to fit certain predatory niches is not trivial and can ultimately be answered only by full comparative analysis of multiple predatory genomes, although there is little evidence of recent horizontal gene transfer in the Bdellovibrio bacteriovorus HD100 genome. Gliding motility genes are implicated in myxococcal motility, but these systems seem to be not present in Bdellovibrio, or they were made redundant so long ago that the genes involved are no longer recognizable as such. Homology searches found no significant homologues of Myxococcus genes involved in gliding. Bdellovibrio preys upon only gram-negative bacteria, albeit a wide range of these, as it penetrates the outer layers and enters the periplasmic space of its prey. By far the largest group of hydrolases in both bacteria is proteases; this probably reflects the importance to predatory bacteria in breaking down prey proteins for uptake and consumption by the predator.