Yersinia pseudotuberculosis BarA-UvrY Two-Component Regulatory System Represses Biofilms via CsrB

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Biofilm formation in Yersinia species is crucial for pathogenesis and relies on the hmsHFRS genes for extracellular matrix production.
• Yersinia pseudotuberculosis (Yptb) produces significantly less extracellular matrix (Hms-ECM) than Yersinia pestis, despite identical hmsHFRS gene sequences.
• The precise regulatory mechanisms governing Yptb biofilm formation and Hms-ECM production are not fully elucidated.

Purpose of the Study:

• To identify negative regulators of biofilm production in Yersinia pseudotuberculosis.
• To investigate the role of the BarA/UvrY two-component system and CsrB regulatory RNA in Yptb biofilm formation.
• To characterize downstream targets of the BarA/UvrY system and their impact on Yptb virulence and biofilm composition.

Main Methods:

• Genetic inactivation of the BarA/UvrY two-component system and CsrB regulatory RNA.
• Congo Red dye binding assays to assess extracellular polysaccharide production.
• Biofilm cohesion assays and flea infection models (Xenopsylla cheopis).
• Flow cytometry for lectin binding analysis and proteomic analysis of csrB mutant strains.

Main Results:

• Inactivation of BarA/UvrY or CsrB increased Congo Red binding and biofilm cohesion in Yptb.
• Disruption of uvrY reduced Yptb toxicity to fleas but did not cause proventricular blockage.
• Proteomic analysis revealed decreased urease subunit abundance and activity in csrB mutants, potentially reducing flea toxicity.
• CsrB loss impacted regulatory proteins, including RcsB, suggesting its involvement in CsrB-mediated biofilm regulation.

Conclusions:

• The Yptb BarA/UvrY two-component system, via activation of CsrB, exerts pleiotropic effects on biofilm production and stability.
• Significant regulatory and compositional differences exist in biofilms produced by Yptb compared to Y. pestis.
• The identified regulators provide insights into the complex control of Yptb biofilm formation and its implications for host-pathogen interactions.