CRP Is an Activator of Yersinia pestis Biofilm Formation that Operates via a Mechanism Involving gmhA and waaAE-coaD.

Lei Liu,Huiying Yang,Dongsheng Zhou,Haihong Fang,Yanping Han,Yiquan Zhang,Ruifu Yang

doi:10.3389/fmicb.2016.00295

Lei Liu, Huiying Yang + Show 5 more

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https://doi.org/10.3389/fmicb.2016.00295

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Abstract

gmhA encodes a phosphoheptose isomerase that catalyzes the biosynthesis of heptose, a conserved component of lipopolysaccharide (LPS). GmhA plays an important role in Yersinia pestis biofilm blockage in the flea gut. waaA, waaE, and coaD constitute a three-gene operon waaAE-coaD in Y. pestis. waaA encodes a transferase that is responsible for binding lipid-A to the core oligosaccharide of LPS. WaaA is a key determinant in Y. pestis biofilm formation, and the waaA expression is positively regulated by the two-component regulatory system PhoP/PhoQ. WaaE is involved in LPS modification and is necessary for Y. pestis biofilm production. In this study, the biofilm-related phenotypic assays indicate that the global regulator CRP stimulates Y. pestis biofilm formation in vitro and on nematodes, while it has no regulatory effect on the biosynthesis of the biofilm-signaling molecular 3′,5′-cyclic diguanosine monophosphate. Further gene regulation experiments disclose that CRP does not regulate the hms genes at the transcriptional level but directly promotes the gmhA transcription and indirectly activates the waaAE-coaD transcription through directly acting on phoPQ-YPO1632. Thus, it is speculated that CRP-mediated carbon catabolite regulation of Y. pestis biofilm formation depends on the CRP-dependent carbon source metabolic pathways of the biosynthesis, modification, and transportation of biofilm exopolysaccharide.

Highlights

Yersinia pestis, the causative agent of plague, is transmitted primarily by fleas and has been responsible for three plague pandemics in human history (Perry and Fetherston, 1997)
The gmhA gene encodes a phosphoheptose isomerase that is required for heptose biosynthesis, a conserved component of the core oligosaccharide, and the deletion of gmhA in Y. pestis leads to inadequate biofilm production for flea blockage (Darby et al, 2005)
Cyclic AMP receptor protein (CRP)-dependent activation of biofilm production was observed in Y. pestis Microtus strain 201, which confirms the results obtained in Y. pestis KIM6+ and CO92 (Willias et al, 2015)

Summary

Introduction

The causative agent of plague, is transmitted primarily by fleas and has been responsible for three plague pandemics in human history (Perry and Fetherston, 1997). Lipopolysaccharide (LPS) is an integral component of the outer membrane of Gram-negative bacteria It is composed of three domains: lipid-A, core oligosaccharide, and O-specific antigen or O side chain. The gmhA gene encodes a phosphoheptose isomerase that is required for heptose biosynthesis, a conserved component of the core oligosaccharide, and the deletion of gmhA in Y. pestis leads to inadequate biofilm production for flea blockage (Darby et al, 2005). The waaA gene encodes a Kdo transferase involved in the attachment of lipid-A to the core oligosaccharide, and waaA mutants show a severely biofilm-defective phenotype of Y. pestis (Tan and Darby, 2005). The waaE gene encodes a protein that is required for adding a substitution on the inner core heptose, and the waaE deletion leads to 40% attenuation of biofilm production of Y. pestis (Izquierdo et al, 2002)

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