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Title: RNPP-type quorum sensing in Clostridium acetobutylicum
Author: Kotte, Ann-Katherine
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2013
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Clostridium acetobutylicum is a Gram-type positive, strictly fennentative, endospore-forming bacterium. It gains energy by converting sugars into organic acids during the first part of its life cycle and into solvents during the second part. This work investigated whether RNPP-type quorum sensing is involved in the regulation of key features such as solventogenesis and sporulation. It identified eight putative RNPP-type Quorum ,S,ensing ,S,ystems (qssA to qssH) in the genome of C. acetobutylicul11, each consisting of a putative Quorum ,S,ensing Regulator (qsr) and Quorum ,S,ensing E.eptide (qsp). ClosTron inactivation of six regulators negatively affected solventogenesis, morphological development or sporulation, whereas inactivation of qsrB had a positive effect. Synthetic QspB-derived pep tides could relieve the repression of solvent formation in a qsrB-overexpressing strain, suggesting that QsrB and QspB fonn a functional quorum sensing system. Two orphan Qsr-type regulators, qsrl and qsrJ, were identified. These regulators are encoded without qsp homologues in a gene cluster that is conserved among the genus Clostridium sensu stricto with qsrl preceding qsrJ. qsrl and qsrJ knockout mutants resembled spoOA mutants as total solvent formation was reduced to below 15 mM and sporulation or granulose accumulation did not occur. The phenotypic changes were con finned at transcriptional level by an RNA-Seq analysis, which also revealed that over 600 genes were significantly differentially regulated, including genes encoding secreted proteins and the Agr-type quorum sensing system. Co-culture and cross streak experiments provided further evidence that QsrI controls the Agrtype and possibly other quorum sensing systems. Key outcomes of this work are the evidence that RNPP-type quorum sensing extends to anaerobic FiJ'micutes and that solvent formation in a Clostridium sp. is controlled by quorum sensing. The discovery of the regulators QrsI and QsrJ was of major importance, showing that other master regulators ex ist beside SpoOA.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available