Effect of growth conditions and substratum composition on the persistence of coliforms in mixed-population biofilms.

Laboratory reactors operated under oligotrophic conditions were used to evaluate the importance of initial growth rate and substratum composition on the long-term persistence of coliforms in mixed-population biofilms. The inoculum growth rate had a dramatic effect on the ability of coliforms to remain on surfaces. The most slowly grown coliforms (mu = 0.05/h) survived at the highest cell concentration. Antibody staining revealed that Klebsiella pneumoniae existed primarily as discrete microcolonies on the surface. Both coliforms and heterotrophic plate count bacteria were supported in larger numbers on a reactive substratum, mild steel, than on polycarbonate.