The Role of Porin Proteins and ygiU-nhaR in the Formation of Biofilm in Escherichia coli.

This study aimed to investigate the roles of porin proteins (OmpA, OmpC, OmpF, OmpG, OmpT, LamB, and PhoE) in biofilm formation in Escherichia coli. The effect of environmental factors such as pH (5.5, 6.0, 6.5, 7.0, 7.5, and 8.0) and biologically essential metal ions (copper, nickel, and zinc) on biofilm formation was also revealed. The ompA, ompC, and lamB porin mutants formed biofilms at different pH values, whereas no biofilm formation was detected in the wild type and ompF, ompG, ompT, and phoE mutants. While the ompC mutant formed a biofilm across a wide pH range (5.5-8.0), the ompA mutant formed a medium-level biofilm at pH values between 6.5 and 8.0. It was observed that the lamB mutant strain produced biofilm only at pH 7.0 and 7.5. Biofilm formation in the ompA and lamB mutants showed little change following metal supplementation, whereas increased biofilm formation was observed in the ompC mutant in the presence of copper and nickel. The biofilm formed in mutants was inhibited in the presence of zinc. Altered expression of nhaR, particularly ygiU, was found to be associated with biofilm formation. In the ompA, ompC, and lamB porin-deficient strains, increased ygiU expression and, to a lesser extent, altered nhaR expression were observed. Considering all these results, it can be concluded that E. coli W3110, which does not produce biofilms under normal physiological conditions, may acquire a biofilm-forming phenotype following mutations in porin genes.