Dataset Information

Salmonella biofilm development depends on the phosphorylation status of RcsB.

ABSTRACT: The Rcs phosphorelay pathway is a complex signaling pathway involved in the regulation of many cell surface structures in enteric bacteria. In response to environmental stimuli, the sensor histidine kinase (RcsC) autophosphorylates and then transfers the phosphate through intermediary steps to the response regulator (RcsB), which, once phosphorylated, regulates gene expression. Here, we show that Salmonella biofilm development depends on the phosphorylation status of RcsB. Thus, unphosphorylated RcsB, hitherto assumed to be inactive, is essential to activate the expression of the biofilm matrix compounds. The prevention of RcsB phosphorylation either by the disruption of the phosphorelay at the RcsC or RcsD level or by the production of a nonphosphorylatable RcsB allele induces biofilm development. On the contrary, the phosphorylation of RcsB by the constitutive activation of the Rcs pathway inhibits biofilm development, an effect that can be counteracted by the introduction of a nonphosphorylatable RcsB allele. The inhibition of biofilm development by phosphorylated RcsB is due to the repression of CsgD expression, through a mechanism dependent on the accumulation of the small noncoding RNA RprA. Our results indicate that unphosphorylated RcsB plays an active role for integrating environmental signals and, more broadly, that RcsB phosphorylation acts as a key switch between planktonic and sessile life-styles in Salmonella enterica serovar Typhimurium.

SUBMITTER: Latasa C

PROVIDER: S-EPMC3393492 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Salmonella biofilm development depends on the phosphorylation status of RcsB.

Latasa Cristina C García Begoña B Echeverz Maite M Toledo-Arana Alejandro A Valle Jaione J Campoy Susana S García-del Portillo Francisco F Solano Cristina C Lasa Iñigo I

Journal of bacteriology 20120511 14

The Rcs phosphorelay pathway is a complex signaling pathway involved in the regulation of many cell surface structures in enteric bacteria. In response to environmental stimuli, the sensor histidine kinase (RcsC) autophosphorylates and then transfers the phosphate through intermediary steps to the response regulator (RcsB), which, once phosphorylated, regulates gene expression. Here, we show that Salmonella biofilm development depends on the phosphorylation status of RcsB. Thus, unphosphorylated ...[more]

PMID: 22582278

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Project description:Enterobacteriaceae produce amyloid proteins called curli that are the major proteinaceous component of biofilms. Amyloids are also produced by humans and are associated with diseases such as Alzheimer's. During the multistep process of amyloid formation, monomeric subunits form oligomers, protofibrils, and finally mature fibrils. Amyloid β oligomers are more cytotoxic to cells than the mature amyloid fibrils. Oligomeric intermediates of curli had not been previously detected. We determined that turbulence inhibited biofilm formation and that, intriguingly, curli aggregates purified from cultures grown under high-turbulence conditions were structurally smaller and contained less DNA than curli preparations from cultures grown with less turbulence. Using flow cytometry analysis, we demonstrated that CsgA was expressed in cultures exposed to higher turbulence but that these cultures had lower levels of cell death than less-turbulent cultures. Our data suggest that the DNA released during cell death drives the formation of larger fibrillar structures. Consistent with this idea, addition of exogenous genomic DNA increased the size of the curli intermediates and led to binding to thioflavin T at levels observed with mature aggregates. Similar to the intermediate oligomers of amyloid β, intermediate curli aggregates were more cytotoxic than the mature curli fibrils when incubated with bone marrow-derived macrophages. The discovery of cytotoxic curli intermediates will enable research into the roles of amyloid intermediates in the pathogenesis of Salmonella and other bacteria that cause enteric infections.IMPORTANCE Amyloid proteins are the major proteinaceous components of biofilms, which are associated with up to 65% of human bacterial infections. Amyloids produced by human cells are also associated with diseases such as Alzheimer's. The amyloid monomeric subunits self-associate to form oligomers, protofibrils, and finally mature fibrils. Amyloid β oligomers are more cytotoxic to cells than the mature amyloid fibrils. Here we detected oligomeric intermediates of curli for the first time. Like the oligomers of amyloid β, intermediate curli fibrils were more cytotoxic than the mature curli fibrillar aggregates when incubated with bone marrow-derived macrophages. The discovery of cytotoxic curli intermediates will enable research into the roles of amyloid intermediates in the pathogenesis of Salmonella and other bacteria that cause enteric infections.

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Salmonella biofilm development depends on the phosphorylation status of RcsB.

Publications

Salmonella biofilm development depends on the phosphorylation status of RcsB.

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