[Regulation of biofilm formation in Escherichia coli K12: effect of mutations in HNS, StpA, lon, and rpoN genes].

More than 99% of bacteria exist in natural ecosystems as specifically organized biofilms adhering to solid surfaces. Biofilms have a typical architecture and are enclosed in exopolymeric matrix. Bacteria living in biofilms are extremely resistant to antibacterial factors. In this work we studied the role of some global regulators of gene expression on biofilm formation by Escherichia coli K12. The Histone-like proteins H-NS and StpA were shown to play an essential role in the regulation of biofilm formation. Mutant strains deficient in HNS or StpA had lower levels of biofilm formation than the wild-type isogenic strain. A double mutant deficient in the two proteins was virtually incapable of forming the biofilms. The mutations in the rpoN gene encoding for the sigma N subunit of RNA-polymerase and in lon gene encoding for Lon-proteinase induced a 40-60% increase in the biofilm formation.