The molecular mechanism of biofilm formation by Salmonella Typhimuriun DT104 was characterized for a better understanding of its attachment and colonization in food processing environments. A library of random mutagenized clones was screened for phenotypic analyses of their ability to form biofilm, pellicle, curli, and cellulose. The genes identified were involved in lipopolysaccharide synthesis, assembly of flagella, regulation of rRNA biosynthesis, and outer membrane transportation and signaling. The insertion of transposon in flgK, rfbA, nusB, and pnp genes resulted in decreased biofilm formation. Alterations of flagellar and lipopolysaccharide production were confirmed in the flgK mutant and rfbA mutant, respectively. Biofilm formation by these four mutants in meat and poultry broths and their attachment on surfaces of stainless steel and glass were significantly reduced compared with those of the wild-type strain (P < 0.05). On the contrary, the mutation of STM4263 and yjcC genes in Salmonella Typhimuriun DT104 resulted in increased biofilm formation and attachment of the species in tested broths and on contact surfaces. Our findings suggest that many factors, such as production of exopolymeric substances and their efficient transportation through outer membrane, expression of flagella, and regulation of exoribonucleases and RNA-binding protein, could be involved in biofilm formation and attachment of Salmonella Typhimurium DT104 on contact surfaces.
Characterization of the protein fraction of the extracellular polymeric substances of three anaerobic granular sludges
