Investigating Bdellovibrio predation: novel isolates and bioinformatics studies of predatory enzymes

Bdellovibrio are predatory bacteria that replicate within the periplasm of their Gram-negative bacterial prey. They exhibit a biphasic lifestyle existing as free-swimming cells and inter-periplasmic growing cells. There is great interest in Bdellovibrio spp. due to their potential as antibacterial therapeutics in the current era of increasing levels of antibiotic resistance. These predators are ubiquitous in nature, being found in environments from freshwater, to soil, to the GI tracts of humans. This study isolated novel Bdellovibrio spp. from the GI tract of farm animals and completed initial characterization of these isolates: one isolate from reindeer was found to have greater predation efficiency in a microaerophilic environment and at 37 oC, which contrasts with the well-characterized strains of Bdellovibrio bacteriovorus which grow best in an aerobic environment at 29 °C. This isolate represents the first reported Bdellovibrio spp. that preferentially undergoes a predatory lifecycle under microaerophilic conditions. This study has led us to hypothesize that isolation of novel Bdellovibrio isolates from the proposed environment for future applications may result in the identification of new strains that may be more optimal for future use because they are more likely to have adapted to the environmental conditions they would encounter. The Bdellovibrio bacteriovorus HD100 genome encodes a large catalogue of hydrolytic enzymes which are hypothesized to play a major role in the degradation of the contents of prey cells for uptake as nutrients for growth by the Bdellovibrio. In this study a bioinformatics approach was used to further classify and group these enzymes by similar domain structure. Potential predatory candidates were identified based on previous transcriptomic studies to determine putative roles of each enzyme within the predatory lifecycle. This study will guide the direction of future molecular studies into the functions of the Bdellovibrio enzyme catalogue. This work has combined experimental and bioinformatic approaches to study the diversity of Bdellovibrio and other predatory bacteria as well as the genomic complement of hydrolytic enzymes they encode. Taken together, these two approaches have highlighted the potential of Bdellovibrio as both an antimicrobial in itself and as a putative source of putative antibacterial enzymes