Using Microfluidics to Explore Chemotaxis by the Predatory Bacterium Bdellovibrio Bacteriovorus

Abstract

Bdellovibrio bacteriovorus is a Gram-negative proteobacterium that preys upon a wide variety other Gram-negative bacteria in the environment. Sensing of and movement toward suitable prey is likely critical to survival of a predator, and indeed, twenty chemotaxis receptors and the associated signaling and flagellar proteins have been discovered in the Bdellovibrio genome. Nevertheless, Bdellovibrio chemotaxis has never been demonstrated using conventional assays, and the molecules that bind to its chemotaxis receptors have not yet been identified. We are using microfluidics to explore chemotaxis in individual Bdellovibrio predators. Microfluidics focuses on creating devices for controlling fluid at the micrometer scale, where fluid interfaces and concentration gradients can be finely manipulated. In this study, we designed and fabricated a microfluidic device within which gradients of sugars, metabolites, signaling molecules, and other molecules of interest can be established. Bdellovibrio predators are introduced to the gradient and are allowed to move in response to the molecules in their environment. Unlike conventional assays that measure chemotaxis as a “yes/no” response, relative degrees of response to molecular stimuli and negative responses can also be measured within this microfluidic device. Movement of the predatory bacteria within these gradients should provide critical information about the molecules responsible for Bdellovibrio chemotaxis toward prey.