Development of a novel system for isolating genes involved in predator-prey interactions using host independent derivatives of Bdellovibrio bacteriovorus 109J.

Adrian A Medina,Robert M Shanks,Daniel E Kadouri

doi:10.1186/1471-2180-8-33

Adrian A Medina, Robert M Shanks + Show 1 more

Open Access

https://doi.org/10.1186/1471-2180-8-33

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Abstract

BackgroundBdellovibrio bacteriovorus is a gram-negative bacterium that preys upon other gram-negative bacteria. Although the life cycle of Bdellovibrio has been extensively investigated, very little is known about the mechanisms involved in predation.ResultsHost-Independent (HI) mutants of B. bacteriovorus were isolated from wild-type strain 109J. Predation assays confirmed that the selected HI mutants retained their ability to prey on host cells grown planktonically and in a biofilm. A mariner transposon library of B. bacteriovorus HI was constructed and HI mutants that were impaired in their ability to attack biofilms were isolated. Transposon insertion sites were determined using arbitrary polymerase chain reaction. Ten HI transposon mutants mapped to genes predicted to be involved in mechanisms previously implicated in predation (flagella, pili and chemotaxis) were further examined for their ability to reduce biofilms.ConclusionIn this study we describe a new method for isolating genes that are required for Bdellovibrio biofilm predation. Focusing on mechanisms that were previously attributed to be involved in predation, we demonstrate that motility systems are required for predation of bacterial biofilms. Furthermore, genes identified in this study suggest that surface gliding motility may also play a role in predation of biofilms consistent with Bdellovibrios occupying a biofilm niche. We believe that the methodology presented here will open the way for future studies on the mechanisms involved in Bdellovibrio host-prey interaction and a greater insight of the biology of this unique organism.

Highlights

Bdellovibrio bacteriovorus is a gram-negative bacterium that preys upon other gramnegative bacteria
In order to assess the facultative behavior of the HI mutants and to demonstrate that the mutants retained their ability to attack surface attached and planktonicly grown host cells, three random HI mutants (HI-A, B, C) were spotted on a lawn of host bacteria
The E. coli biofilms were exposed for 48 hr to the HI mutants, B. bacteriovorus lysate or DDNB

Summary

Introduction

Bdellovibrio bacteriovorus is a gram-negative bacterium that preys upon other gramnegative bacteria. The life cycle of Bdellovibrio has been extensively investigated, very little is known about the mechanisms involved in predation. Bdellovibrios are largely found in wet, aerobic environments and were first isolated from soil in the early 1960's, where they are commonly encountered [1]. They can be found in fresh and brackish water, sewage, and seawater [2,3,4,5]. The life cycle of Bdellovibrio has been extensively investigated, very little is known about the mechanisms involved in predation and the genetic network regulating the developmental stages of Bdellovibrio. Other mechanisms implicated in predation include motility and chemotaxis [9,10,11]

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