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Title:   Author  item
                                            Sharma, Vijayitem
                                            Bearson, Shawnitem
                                            Bearson, Bradley

                                                         - *Brad*
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 2/20/2009
                                    Publication  Date: 5/18/2009
                                    Citation: Sharma, V.K., Bearson, S.M., Bearson, B.L. 2009. Evaluating the Role of SDIA and HHA in Enhanced Adherence of a SDIA HHA Double Mutant of Enterohemorrhagic Escherichia coli O157:H7 [abstract]. American Society for Microbiology Meeting. Paper No. B108.Interpretive Summary:
                                Technical Abstract: Adherence of Enterohemorrhagic Escherichia coli (EHEC) O157:H7 to biotic (epithelial cells) and abiotic surfaces (biofilm formation) proceeds from an initial reversible adherence to an irreversible stage of intimate adherence. While flagella and fimbriae facilitate initial stage of adherence in both types of adherences, the factors encoded by the locus of enterocyte effacement (LEE) result in intimate attachment of EHEC O157:H7 to epithelial cells. Both biotic and abiotic adherence processes require a diverse array of genes whose expressions are tightly and temporally regulated via a variety of regulatory networks. Quorum-sensing-mediated regulation of flagellar genes, for example, plays an important role in both cellular adherence and biofilm formation. The increased expression of sdiA (luxR homologue) in response to specific signals or when supplied on a multicopy plasmid has been shown to exert negative control on the expression of flagellar genes and LEE-encoded EspD and intimin, respectively. Earlier studies have shown that hha exerts negative effect on the expression of fimbrial and LEE-encoded genes required for biofilm biogenesis and adherence to epithelial cells, respectively. In order to understand the impact of sdiA and hha on adherence, EHEC O157:H7 sdiA hha mutant was analyzed for its adherence to HEp-2 cells relative to the wild-type, sdiA, and hha mutant strains. We found increases of 2-, 8-, and 10-fold in the adherence of sdiA, hha, and sdiA hha mutant strains, respectively, relative to the wild-type strain. Reverse transcriptase-based real-time PCR analysis of RNA from sdiA mutant showed an increase of 1.55-fold in the expression of flagellar gene fliC but the expression of LEE regulator ler and LEE-encoded espA remained unchanged relative to the wild-type strain, indicating that enhanced adherence of sdiA mutant results at least in part from an increased flagellar gene expression. Whether 8- and 10-fold relative increases in the adherence of hha and sdiA hha mutants, respectively, resulted from differential increases in fimbrial, flagellar, and LEE regulon expression remains to be determined.


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