Posted: August 24th, 2011 - 7:34am
Source: Appl. Environ. Microbiol. doi:10.1128/AEM.00277-11

The role of curli expression in attachment of E. coli O157:H7 to glass, Teflon and stainless steel (SS) was investigated through the creation of csgA knockout mutants in two isolates of E. coli O157:H7. Attachment assays using epifluorescence microscopy and adhesion force measurements of bacterial cells to the substrates using atomic force microscopy (AFM) force mapping were used to determine differences in attachment between wildtype (wt) and csgA negative ( csgA) strains following growth in four different media. Hydrophobicity of the cells was determined using contact angle measurements (CAM) and bacterial adhesion to hydrocarbons (BATH). Attachment assay results indicated that csgA strains attached to glass, Teflon and SS surfaces in significantly different numbers compared to their wt counterparts in a growth media dependent fashion (p<0.05). However, no clear correlation was seen between attachment numbers, surface type or growth media. No correlation was seen between BATH and CAM results (R2< 0.70). Hydrophobicity differed between wt and csgA in some cases in a growth media and method dependant fashion (p<0.05). AFM force mapping revealed no significant difference in adhesion force to glass and SS surfaces between wt and csgA strains (p>0.05), but a significantly greater adhesion force to Teflon for one of the two wt strains compared with its csgA counterpart (p<0.05). This study shows that CsgA production by E. coli O157:H7 may alter attachment behaviour in some environments, however, further investigation is required in order to determine the exact relationship between CsgA production and attachment to abiotic surfaces.