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Logo of bmcmicrBioMed Centralsearchsubmit a manuscriptregisterthis articleBMC Microbiology
 
BMC Microbiol. 2012; 12: 190.
Published online Sep 3, 2012. doi:  10.1186/1471-2180-12-190
PMCID: PMC3462683
The effect of environmental conditions on expression of Bacteroides fragilis and Bacteroides thetaiotaomicron C10 protease genes
Roibeard F Thornton,#1,2 Elizabeth C Murphy,#1,2,4 Todd F Kagawa,1,2 Paul W O’Toole,3 and Jakki C Cooneycorresponding author1,2
1Department of Life Sciences, University of Limerick, Limerick, Ireland
2Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
3Department of Microbiology, & Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
4Present address: Department of Clinical Sciences, Lund University, Lund, Sweden
corresponding authorCorresponding author.
#Contributed equally.
Roibeard F Thornton: roibeard.thornton/at/gmail.com; Elizabeth C Murphy: elizabeth.murphy/at/med.lu.se; Todd F Kagawa: kagawatf/at/gmail.com; Paul W O’Toole: pwotoole/at/ucc.ie; Jakki C Cooney: jakki.cooney/at/ul.ie
Received December 13, 2011; Accepted August 23, 2012.
Abstract
Background
Bacteroides fragilis and Bacteroides thetaiotaomicron are members of the normal human intestinal microbiota. However, both organisms are capable of causing opportunistic infections, during which the environmental conditions to which the bacteria are exposed change dramatically. To further explore their potential for contributing to infection, we have characterized the expression in B. thetaiotaomicron of four homologues of the gene encoding the C10 cysteine protease SpeB, a potent extracellular virulence factor produced by Streptococcus pyogenes.
Results
We identified a paralogous set of genes (btp genes) in the B. thetaiotaomicron genome, that were related to C10 protease genes we recently identified in B. fragilis. Similar to C10 proteases found in B. fragilis, three of the B. thetaiotaomicron homologues were transcriptionally coupled to genes encoding small proteins that are similar in structural architecture to Staphostatins, protease inhibitors associated with Staphopains in Staphylococcus aureus. The expression of genes for these C10 proteases in both B. fragilis and B. thetaiotaomicron was found to be regulated by environmental stimuli, in particular by exposure to oxygen, which may be important for their contribution to the development of opportunistic infections.
Conclusions
Genes encoding C10 proteases are increasingly identified in operons which also contain genes encoding proteins homologous to protease inhibitors. The Bacteroides C10 protease gene expression levels are responsive to different environmental stimuli suggesting they may have distinct roles in the bacterial-host interaction.
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