ARS | Publication request: Influence of curli expression on biofilm formation and attachment to plant surface by shiga toxigenic E. coli

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: February 9, 2012
Publication Date: June 25, 2012
Citation: Patel, J.R., Macarisin, D., Bauchan, G.R. 2012. Influence of curli expression on biofilm formation and attachment to plant surface by shiga toxigenic E. coli. Annual Meeting of the Institute of Food Technologists. Paper No. 135-03.

Technical Abstract: Shiga-toxigenic Escherichia coli O157:H7 (STEC) outbreaks have been linked to consumption of fresh produce. Bacteria extracellular appendages, such as curli fibers and cellulose may play critical role in STEC biofilm formation and adherence to plant surface. We determined cellulose and curli production by two STEC human disease outbreaks isolates, EDL933 and 86-24, and their isogeinic mutants lacking the ability to produce curli (86-24'csgA; EDL933'csgA; EDL933'csgD), cellulose (EDL933'bcsA) or both (EDL933'csgA/'bcsA). Comparative biofilm growth and quantification assays of nine STEC strains were conducted by the MBECTM Physiology and Genetics Assay (Innovotech Inc) under different growth conditions. The relative attachment strength of STEC strains to spinach plants was calculated based on their attachment to plant surface. Biofilm formation by STEC isolates was strongly correlated with their ability to produce curli fimbriae; no biofilm formation by curli deficient strains was detected under any of the growth conditions tested. Both the composition of nutritive media and temperature greatly influenced the biofim formation by curli-producing strains. Curli over-expressing mutant, 86-24csgDc, produced significantly more biomass (0.47 and 0.72 in 10% TSB and 10% LBNS, respectively) compared to cellulose deficient EDL933'bcsA (0.29 and 0.43 in 10% TSB and 10%LBNS, respectively) at 23ºC. These two strains produced significantly higher biomass at 23 than at 30ºC. In general, 10% LBNS was a superior medium for biofilm formation followed by 10% TSB. Curli-expressing STEC strains 86-24, 86-24csgDc and EDL933'bcsA showed from 2 to 20-fold greater attachment strength to spinach plants as compared to non-curliated strains. Lack of cellulose expression did not affect biofilm production and stronger attachment of EDL933'bcsA strain to spinach leaves. Understanding the role of curli in biofilm formation and STEC attachment to plant surface will be helpful in developing new intervention strategies to remove pathogens from fresh produce.