Role of yifO, agaB, and atoS in Escherichia coli biofilm formation and stress response

Abstract

In nature, bacteria exist predominantly as a surface adherent community referred to as a biofilm, which differs phenotypically from planktonic cells. Alterations in phenotypic expression are essential not only for transition through the various stages of biofilm formation, but also for maintenance. In this study, we sought to elicit differences in phenotypic expression in E. coli biofilms, as well as to characterize several mutants to determine if expression is essential for biofilm formation. Of the numerous differentially expressed genes identified by gene array analysis, yjfO, agaB, and atoS were selected for further characterization Results from both epifluorescence microscopy and microtiter assays confirmed that all mutant strains displayed a reduction in biofilm formation in comparison to the wild-type E. coli. Additionally, we sought to elicit differences in the viability of both planktonic and biofilm cells following exposure to hydrogen peroxide, pH shifts and elevated temperature Planktonically grown mutant strains exhibited a decreased viability following exposure to acidic pH and hydrogen peroxide, whereas the atoS mutant exhibited an increased viability at elevated temperatures compared to that of the wild-type. Exposure of four day biofilms to hydrogen peroxide resulted in an insignificant decrease in biofilm mass for all strains, whereas exposure to acidic pH resulted in a decreased biofilm for only the wild-type and the yjfO mutant. Overall, our results suggest that mutations affecting yjfO, agaB, or atoS lead to a decreased ability to form a biofilm and a decreased ability to survive exposure to hydrogen peroxide and acidic pH when grown planktonically.