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United States Department of Agriculture

Agricultural Research Service

Research Project: PREVENTION AND CHARACTERIZATION OF PERSISTENT COLONIZATION BY E. COLI O157:H7 AND OTHER SHIGA TOXIN-PRODUCING E. COLI (STEC) IN CATTLE Title: Transpositional inactivation of gadW enhances curli production and biofilm formation in Enterohemorrhagic Escherichia coli O157:H7

item Sharma, Vijay

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 3, 2014
Publication Date: N/A

Technical Abstract: Enterohemorrhagic Escherichia coli (EHEC) O157:H7 has been shown to produce variants that either express or are repressed in the expression of curli fimbriae promoting bacterial attachment, aggregation, and biofilm formation. The variant expression of curli fimbriae in some instances could result from increased or reduced expression of csgBAC and csgDEFG, two divergently transcribed operons that are regulated directly by many global transcriptional regulators and indirectly through the activity of two-component signal transduction systems in response to a variety of environmental and nutritional stimuli. In this study, we report that GadW, an AraC family of transcriptional regulators, controls curli expression and biofilm formation in a curli-repressed variant of EHEC O157:H7. The gadW gene was identified by screening a library of transposon mutants for their ability to bind Congo red in media and under growth conditions conducive for curli biogenesis. Several transposon mutants were identified that showed increased Congo red binding compared to the parent strain. The nucleotide sequence analysis of the chromosomal regions flanking the chromosomally integrated transposon resulted in the identification of gadW as the transposon insertion site in these increased Congo red binding mutants. Enhanced Congo red binding of gadW mutants correlated with their increased curli production and biofilm formation. Based on the positive regulation by GadW of GadE that in turn activates glutamate-dependent acid resistance pathway, we inferred that curli production and biofilm formation in the curli-repressed variant has inverse correlation with the expression of GadW and acid resistance pathway in EHEC O157:H7.

Last Modified: 8/25/2016
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