AUTHOR=Schachterle Jeffrey K. , Stewart Ryan M. , Schachterle M. Brett , Calder Joshua T. , Kang Huan , Prince John T. , Erickson David L. 

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

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2018.00323

DOI=10.3389/fcimb.2018.00323

ISSN=2235-2988

ABSTRACT=<p>The formation of biofilms by <italic>Yersinia pseudotuberculosis</italic> (<italic>Yptb</italic>) and <italic>Y. pestis</italic> requires the <italic>hmsHFRS</italic> genes, which direct production of a polysaccharide extracellular matrix (Hms-ECM). Despite possessing identical <italic>hmsHFRS</italic> sequences, <italic>Yptb</italic> produces much less Hms-ECM than <italic>Y. pestis</italic>. The regulatory influences that control <italic>Yptb</italic> Hms-ECM production and biofilm formation are not fully understood. In this study, negative regulators of biofilm production in <italic>Yptb</italic> were identified. Inactivation of the BarA/UvrY two-component system or the CsrB regulatory RNA increased binding of Congo Red dye, which correlates with extracellular polysaccharide production. These mutants also produced biofilms that were substantially more cohesive than the wild type strain. Disruption of <italic>uvrY</italic> was not sufficient for <italic>Yptb</italic> to cause proventricular blockage during infection of <italic>Xenopsylla cheopis</italic> fleas. However, this strain was less acutely toxic toward fleas than wild type <italic>Yptb</italic>. Flow cytometry measurements of lectin binding indicated that <italic>Yptb</italic> BarA/UvrY/CsrB mutants may produce higher levels of other carbohydrates in addition to poly-GlcNAc Hms-ECM. In an effort to characterize the relevant downstream targets of the BarA/UvrY system, we conducted a proteomic analysis to identify proteins with lower abundance in the <italic>csrB</italic>::Tn5 mutant strain. Urease subunit proteins were less abundant and urease enzymatic activity was lower, which likely reduced toxicity toward fleas. Loss of CsrB impacted expression of several potential regulatory proteins that may influence biofilms, including the RcsB regulator. Overexpression of CsrB did not alter the Congo-red binding phenotype of an <italic>rcsB</italic>::Tn5 mutant, suggesting that the effect of CsrB on biofilms may require RcsB. These results underscore the regulatory and compositional differences between <italic>Yptb</italic> and <italic>Y. pestis</italic> biofilms. By activating CsrB expression, the <italic>Yptb</italic> BarA/UvrY two-component system has pleiotropic effects that impact biofilm production and stability.</p>