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Open Access Research article

Mutagenesis of RpoE-like sigma factor genes in Bdellovibrio reveals differential control of groEL and two groES genes

Carey Lambert1, Rob Till1, Laura Hobley12 and R Elizabeth Sockett1*

Author Affiliations

1 Centre for Genetics and Genomics, School of Biology, University of Nottingham Medical School, QMC, Derby Road, Nottingham, NG7 2UH, UK

2 College of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK

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BMC Microbiology 2012, 12:99  doi:10.1186/1471-2180-12-99

Published: 7 June 2012

Abstract

Background

Bdellovibrio bacteriovorus HD100 must regulate genes in response to a variety of environmental conditions as it enters, preys upon and leaves other bacteria, or grows axenically without prey. In addition to “housekeeping” sigma factors, its genome encodes several alternate sigma factors, including 2 Group IV-RpoE-like proteins, which may be involved in the complex regulation of its predatory lifestyle.

Results

We find that one sigma factor gene, bd3314, cannot be deleted from Bdellovibrio in either predatory or prey-independent growth states, and is therefore possibly essential, likely being an alternate sigma 70. Deletion of one of two Group IV-like sigma factor genes, bd0881, affects flagellar gene regulation and results in less efficient predation, although not due to motility changes; deletion of the second, bd0743, showed that it normally represses chaperone gene expression and intriguingly we find an alternative groES gene is expressed at timepoints in the predatory cycle where intensive protein synthesis at Bdellovibrio septation, prior to prey lysis, will be occurring.

Conclusions

We have taken the first step in understanding how alternate sigma factors regulate different processes in the predatory lifecycle of Bdellovibrio and discovered that alternate chaperones regulated by one of them are expressed at different stages of the lifecycle.