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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #313906

Title: Assessing the relative contributions of EspA and CsgA in cellular adherence and biofilm formation of enterohemorrhagic Escherichia coli O157:H7

item Sharma, Vijay
item Kudva, Indira

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2015
Publication Date: 5/30/2015
Citation: Sharma, V.K., Kudva, I.T. 2015. Assessing the relative contributions of EspA and CsgA in cellular adherence and biofilm formation of enterohemorrhagic Escherichia coli O157:H7 [abstract]. 115th General Meeting of the American Society for Microbiology, May 30-June 2, 2015, New Orleans, Louisiana. p. 164.

Interpretive Summary:

Technical Abstract: In enterohemorrhagic Escherichia coli O157:H7 (O157), the locus of enterocyte effacement (LEE) encodes a type III secretion system with an extracellular filamentous structure consisting of the polymerized translocator protein EspA. The EspA filaments provide transient interactions between bacterial and host cells and serve as conduits for the translocation of effector proteins into host cells, the processes needed for the intimate bacterial adherence and formation of attaching and effacing lesions. In previous studies, we demonstrated that the hha deletion mutant of O157 adhered to HEp-2 cells at a much higher magnitude and produced a greater biofilm biomass on a polystyrene substratum. Transcriptional analysis of the hha mutant revealed increases in the expression of LEE, including EspA, and CsgA which is required for curli biosynthesis and biofilm formation. In the present study, we constructed hha espA, hha csgA, and hha espA csgA deletion mutants and compared these to the parental and hha mutant strains in order to determine the relative importance of EspA and CsgA in adherence to HEp-2 cells and biofilm formation in media containing or lacking glucose. When assayed in a tissue culture medium containing glucose, espA, but not csgA, was determined to be essential for adherence to HEp-2 cells since espA mutants showed significantly lower adherence compared to the hha mutant and the espA mutants complemented with an EspA-expressing plasmid. Since none of these strains produced significant amount of biofilm in a glucose-supplemented medium compared to the high levels of biofilm produced by these strains in media lacking glucose, which agrees with the reported inhibitory effects of glucose on biofilm formation and presumably curli production, we assessed the adherence of these strains to HEp-2 cells in a medium lacking glucose. Under these assay conditions, csgA not only enhanced adherence of O157 to HEp-2 cells independent of espA but the magnitude of the effect of csgA on adherence appeared higher than that of espA. These results indicate that both EspA and CsgA could contribute to the adherence of O157 to epithelial cells, albeit under conditions that presumably are better suited to the expression of EspA or CsgA-containing regulons.