Exploration of Bdellovibrio Chemotaxis and Predation using Microfluidics

Abstract

Bdellovibrio bacteriovorus is a predatory, gram-negative bacterium that preys on other gram-negative bacteria. It has long been hypothesized that B. bacteriovorus can sense prey in the environment and move toward them, and recent genomic sequencing indicates that B. bacteriovorus has approximately 20 methyl-accepting chemotaxis receptor proteins and the full flagellar machinery necessary for chemotaxis. Nonetheless, B. bacteriovorus chemotaxis has never been demonstrated in the laboratory. As a result, the molecules it might use to target and track its prey have not been identified. A road block to prior research has been the limitations on traditional chemotaxis assays; B. bacteriovorus does not form colonies on agar media plates and it has been known to move up to 100 body lengths per second, which makes it difficult to track its growth or movement in response to a specific chemoeffector.To address these issues, we have designed a microfluidic device to measure the reaction of B. bacteriovorus to specific chemoeffectors. The small dimensions and controlled flow in a microfluidic device allow us to introduce B. bacteriovorus to a gradient of chemoeffectors such as sugars, metabolites, and signaling molecules. With multiple outlets containing a range of chemoeffector concentrations, we can observe both attractive and repellent responses, as well as score the degree to which B. bacteriovorus reacts to these chemicals. Thus a microfluidic device provides significant advances over classic “on/off” chemotaxis assays, allowing us to explore for the first time the target molecules and affinity of B. bacteriovorus chemotaxis receptors.