Laser trap studies of end-on E. coli adhesion to glass.

Rod-shaped Escherichia coli K12:D21 bacteria were previously found to adhere by their ends (poles) [J.F. Jones, J.D. Feick, D. Imoudu, N. Chukwumah, M. Vigeant, D. Velegol, Appl. Environ. Microbiol. 69 (2003) 6515.]. In the current study we used a Nd:YAG 1064 nm laser trap to quantify the fraction of adherent bacteria and the time scale for the adhesion to occur. For the E. coli studied, 15.9+/-3.4% of the bacteria adhered when presented end-on for 15s to a cleaned glass surface that was not treated for specific interactions. These bacteria were found to adhere either instantaneously (approximately <1s) or not at all, and the adhesion was shown to be independent of power (force) of the laser trap. Additionally, for a given bacterium, either 0 or 1 ends were adhesive, never both ends. It is hypothesized that the end-on adhesion of D21 is related to bacterial polarity that dynamically results from the division process. We studied the reattachment of cells after adhesion and subsequent removal, finding that most bacteria reattach, some at least five times. However, a small fraction of D21 did not reattach after the first removal. Bacterial cells with observable division planes were tested for end-on adhesion; none of the 18 cells studied adhered by either end. On the other hand, we examined 50 daughter cells immediately after division, and four of the cells were adhesive. End-on adhesion is shown to be an important initial adhesion strategy for the E. coli strain via a single end with adhesion occurring instantaneously. Knowledge about adherent nanodomains (here, on one end) on bacteria will lead to better predictions of sticking coefficients and bacteria transport through porous media.