Quorum sensing (QS) is a cell-to-cell communication mechanism that allows bacterial cells to collectively behave like a multicellular organism. It regulates the expression of toxoflavin, one of the major virulence factors of the rice pathogen, Burkholderia glumae. The QS system of B. glumae is mediated by the core genes, tofI and tofR. N-octanoyl-L-homoserine lactone, the primary QS signal molecule of B. glumae, is synthesized by tofI and binds to the cognate receptor tofR at the quorum point. However, tofI and tofR null mutants produce toxoflavin in certain growth conditions, indicating the presence of tofI- and tofR-independent pathways for toxoflavin production. The present study identified regulators required for the tofI- and tofR-independent pathways, including flagella transcriptional activator, diguanylate cyclase, O-antigen polymerase family protein, QsmR QS-dependent master regulator and one hypothetical protein with its encoding gene located upstream of toxJ (encoding toxoflavin production activator). A novel QS regulatory element, tofM, was identified as a positive regulator of pathogenicity and a putative modulator of tofR in B. glumae. RNA-sequencing was also performed to investigate the QS regulon and medium condition-dependent gene expression in B. glumae. A large collection of target genes and noncoding RNAs was detected by comparative transcriptome analysis. From a comparison of the transcriptional profile of the wild type (336gr-1) and quorum sensing mutants grown on solid and liquid media, it is postulated that an alternative global regulator is activated to compensate for the dysfunction of AHL QS on solid medium.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11132013-230025 |
| Date | 21 November 2013 |
| Creators | Chen, Ruoxi |
| Contributors | Pettis, Gregg S., Subudhi, Prasanta K., Hoy, Jeffrey W., Valverde, Rodrigo A., Ham, Jong Hyun |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11132013-230025/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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