Universität zu Köln

Dreck, Katrin (2013). Functional characterization of the transcription factor YjjQ in Escherichia coli. PhD thesis, Universität zu Köln.

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Abstract

YjjQ is a FixJ/NarL‐type transcriptional regulator conserved in commensal and various pathogenic bacteria such as enterohaemorrhagic Escherichia coli (EHEC), uropathogenic E. coli (UPEC) as well as Citrobacter and Enterobacter. YjjQ was previously implicated to play a role in bacterial virulence, motility, and adhesion. Microarray analysis performed in E. coli K‐12 and UPEC strain CFT073 revealed that yjjQ overexpression results in significant downregulation of multiple loci. One of the putative loci considerably repressed by YjjQ is the bcs locus dedicated to cellulose synthesis. This exopolysaccharide is a major component of the bacterial extracellular matrix (ECM). Additional ECM constituents are adhesive amyloid fibers called curli. The ECM facilitates cell‐cell and cell‐surface contacts thereby largely contributing to biofilm formation. These surface‐associated multicellular communities represent the prevalent bacterial lifestyle. Wildtype Enterobacteriaceae co‐expressing cellulose and curli exhibit a distinctive colony morphology on Congo Red indicator plates called the red, dry and rough (rdar) morphotype. Putative repression of the bcs locus by YjjQ suggests that this transcription factor may affect ECM composition. Therefore the effect of YjjQ expression on the morphotype of wild‐type and mutant UPEC 536 strains was investigated. YjjQ was found to considerably weaken the rdar morphotype compared to the control. To examine the influence of YjjQ on biofilm formation of wild‐type and mutant E. coli K‐12 and UPEC 536 strains a biofilm assay was performed. YjjQ substantially represses bacterial adhesion to polystyrene. These data suggest that YjjQ acts as a suppressor of multicellular behavior and possibly adhesion of Enterobacteriaceae. Another putative target locus negatively regulated by YjjQ is flhDC encoding the master regulator of flagellar motility. This implies that YjjQ may impinge upon bacterial motility. Therefore the impact of YjjQ on motility of wild‐type and mutant E. coli K‐12 and UPEC 536 strains was investigated. YjjQ was found to substantially repress motility suggesting that besides inhibiting biofilm formation, it also acts as a suppressor of flagellar motility. These newly identified functions of YjjQ indicate that this transcription factor may be an important regulator involved in the network controlling adhesion versus motility.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Dreck, Katrin kdreck@uni-koeln.de UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-52472
Date:	July 2013
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Institute for Genetics
Subjects:	Life sciences
Uncontrolled Keywords:	Keywords Language Biofilm formation; bacterial extracellular matrix; Adhesion; Motility English
Date of oral exam:	8 July 2013
Referee:	Name Academic Title Schnetz, Karin Prof. Dr. Dohmen, Jürgen Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/5247