Biofilm formation in Escherichia coli and regulatory gene expression via quorum sensing systems
| dc.contributor.author | Hernandez-Doria, Juan David | |
| dc.contributor.examiningcommittee | DeKievit, Teresa (Microbiology) Ominski, Kim (Animal Science) Plaizier, Kees J.C (Animal Science) Gray-Owen, Scott D. (Molecular Genetics, University of Toronto) | en_US |
| dc.contributor.supervisor | Krause, Denis (Animal Science) | en_US |
| dc.date.accessioned | 2011-12-12T16:13:26Z | |
| dc.date.available | 2011-12-12T16:13:26Z | |
| dc.date.issued | 2011-12-12 | |
| dc.degree.discipline | Animal Science | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | Bacterial biofilms are microbial communities that adhere to abiotic or biotic surfaces. Biofilm formation (BF) studies in E. coli have primarily concentrated on uropathogenic E. coli, commensal K-12 and enterohemorrhagic E. coli O157:H7. This does not include the vast diversity of environmental strains. Quorum sensing (QS) is a means by which bacteria can communication with one another through the production of signalling molecules. The autoinducer 2 (AI-2) QS system is utilized by E. coli and several other bacterial species for controlling gene expression. The role of AI-2 in E. coli BF varies among different strains. For example in the K-12 strain, AI-2 regulates motility, and thus can affect BF; whereas in O157:H7, AI-2 has a more metabolic role. Interestingly, in strain O157:H7, motility is controlled by a newly discovered QS system regulated by the autoinducer 3 (AI-3) molecule plus the mammalian hormones epinephrine (Epi) and norepinephrine (Ne). The purpose of this study was to investigate the ability of a panel of environmental E. coli strains to form biofilms and to determine whether QS is involved in the process. A new pathotype of E. coli, adherent invasive E. coli (AIEC) which is associated with Crohn’s disease was included in the investigation. Study 1 sought to determine whether BF under different media conditions correlated with the presence of genes involved in the AI-2 QS system or adhesin factors. Media conditions were the principal variable affecting the BF. Study 2 examined the role of the AI-2 and AI-3/Epi/Ne QS systems in motility and BF by the AIEC strain. It was discovered that the AI-3 system is involved in motility; whereas the AI-2 system had no effect on BF or motility. In Study 3, microarray gene expression analysis and invasion assays were performed using qseB or qseC mutants. These genes encode the two-component regulatory system recognizing AI-3 or its cognate, epinephrine. Our findings indicate that alternative pathways likely account for the BF observed for the qseB and qseC mutants. It was concluded that the AI-3/Epi/Ne QS system partially controls AIEC motility and the invasion of epithelial cells. | en_US |
| dc.description.note | February 2012 | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/4995 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | biofilm | en_US |
| dc.subject | quorum sensing | en_US |
| dc.subject | E. coli | en_US |
| dc.title | Biofilm formation in Escherichia coli and regulatory gene expression via quorum sensing systems | en_US |
| dc.type | doctoral thesis | en_US |