The putative influence of the agr operon upon survival mechanisms used by Clostridium acetobutylicum

Abstract

The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.ukThe putative influence of the agr operon upon survival mechanisms used by Clostridium acetobutylicum AbstractThe bacterium Clostridium acetobutylicum produces acids as an energy-yielding process during exponential growth. An acidic environment, however, is toxic to the cells and two survival mechanisms are in place to prevent them from dying. Firstly, during a solventogenesis phase, the cells take up these acids and convert them to solvents, thus raising the environmental pH. Secondly, the cells undergo sporulation to form highly resistant spores capable of surviving extreme conditions. One possible regulatory mechanism for these processes is the accessory gene regulatory (agr ) quorum-sensing system, which is thought to coordinate cell population density with cell phenotype. We model this system to monitor its putative effect upon solventogenesis and the sporulation-initiation network responsible for triggering spore formation. We demonstrate that a high population density should be able to induce both solventogenesis and sporulation, with variations to the parameter set allowing sporulation alone to be triggered; additional distinct signals are capable of restoring the solventogenic response. We compare the agr system of C. acetobutylicum with that of Staphylococcus aureus in order to investigate why the differences in feedback between the two systems may have evolved. Our findings indicate that, depending upon the mechanism of interaction between the agr system and the sporulation-initiation network, the clostridial agr circuitry may be in place either to moderate the number of spores that are formed (in order for this number to reflect the urgency of the situation), or simply as an energy-saving strategy.

Flow cytometry analysis of Clostridium beijerinckii NRRL B-598 populations exhibiting different phenotypes induced by changes in cultivation conditions

“…C. beijerinckii strains, including strain NRRL B-598, generally contain genes for the agr -based quorum sensing system [ 4 ], which was found to be responsible for regulation of sporulation in C. acetobutylicum. At the same time, the agr -based system in C. acetobutylicum did not significantly influence solventogenesis and final solvents titres [ 71 , 72 ].…”

Sporulation in solventogenic and acetogenic clostridia

“…The heat-shock treatment has to be adapted to the species to give the highest germination efficiency. Knowledge of these differences is crucial as it affects germination efficiency after a heatshock treatment before fermentation (Jabbari et al 2013;Li et al 2011;Steiner et al 2012).…”

New Elements To Consider When Modeling the Hazards Associated with Botulinum Neurotoxin in Food

“…A model describing the role of TcdC—an anti-sigma factor transmembrane protein that destabilizes TcdR (an alternative sigma factor that positively regulates toxin production through interactions with RNA polymerase)—in C. difficile toxin gene regulation networks was published recently by Jabbari and colleagues ( 25 ). Other models of the effect of pH-induced gene regulation on solvent production by C. acetobutylicum in continuous culture ( 26 ) and the impact of interactions between the Agr quorum-sensing system and sporulation initiation network on the number of spores formed by C. acetobutylicum ( 27 ) have also been reported. However, no models at the molecular level exist in relation to C. botulinum .…”