Regulation of Biofilm Formation in Salmonella Enterica Serovar Typhimurium

Abstract

In animals, plants and the environment, Salmonella enterica serovar Typhimurium forms the red dry and rough (rdar) biofilm characterized by extracellular matrix components curli and cellulose. With complex expression control by at least ten transcription factors, the bistably expressed orphan response regulator CsgD directs rdar morphotype development. CsgD expression is an integral part of the Hfq regulon and the complex cyclic diguanosine monophosphate signaling network partially controlled by the global RNA-binding protein CsrA. Cell wall turnover and the periplasmic redox status regulate csgD expression on a post-transcriptional level by unknown mechanisms. Furthermore, phosphorylation of CsgD is a potential inactivation and degradation signal in biofilm dissolution. Including complex incoherent feed-forward loops, regulation of biofilm formation versus motility and virulence is of recognized complexity.

<b><i>Salmonella</i></b> and Reactive Oxygen Species: A Love-Hate Relationship

“…However, the lipid A portion of the LPS molecule is also an activator of innate immunity responses, including induction of iNOS expression [32] and enforcement of the oxidative burst [33]. In addition, salmonella is capable of expressing multiple adhesins that in concert contribute to infection of the mouse [34] and to biofilm formation that adds to the persistent carriage state [35, 36]. …”

“…Salmonella is capable of forming biofilms on gall bladder stones, which is believed to promote establishment of carriage [35], despite constant exposure to bile and hence ROS stress as stipulated above. S .…”

What's on the Outside Matters: The Role of the Extracellular Polymeric Substance of Gram-negative Biofilms in Evading Host Immunity and as a Target for Therapeutic Intervention

“…biofilm matrix is complex and highly variable in response to altered environmental conditions and variable among serovars. The St/Sty polysaccharides identified to date include colanic acid, O-antigen capsule, and cellulose (14,15). Sty produces a distinct polysaccharide, Vi-antigen, a primary marker for infection with this serovar and the basis of several current vaccine approaches.…”

The Rcs-Regulated Colanic Acid Capsule Maintains Membrane Potential in Salmonella enterica serovar Typhimurium

“…Salmonella can form biofilms on biotic and abiotic surfaces, including glass, plastic, gallstones, HEp-2 cells, and chicken intestinal epithelium (31, 56–58). The contribution of the colanic acid capsule to biofilm formation is well established (31, 32), and induction of the Psp response has been observed in biofilms (59).…”

“…Decreased biofilm formation by the wza yjb mutant is also likely to result from absence of the colanic acid capsule, further confirming that this EPS is essential for Salmonella biofilm formation. The red, dry, and rough (RDAR) colony morphotype is indicative of biofilm formation by Salmonella on agar plates containing the dyes Congo red and Coomassie blue (57). WT RDAR colonies are not formed by pspA , wza yjb , or pspA wza yjb mutants (see Fig.…”