CmpX Affects Virulence in Pseudomonas aeruginosa Through the Gac/Rsm Signaling Pathway and by Modulating c-di-GMP Levels.

Anjali Y Bhagirath,Deepti Somayajula,Yanqi Li,Kangmin Duan

doi:10.1007/s00232-017-9994-6

Abstract

Pseudomonas aeruginosa is an ubiquitous organism which is able to infect and colonize many types of hosts including humans. Colonization of P. aeruginosa in chronic infections leads to the formation of biofilms, which are difficult to eradicate. P. aeruginosa is capable of regulating its virulence factors in response to external environment triggers and its signaling mechanism involves two-component regulatory systems and small molecules such as bis-(3'-5')-cyclic dimeric guanosine monophosphate. PA1611-RetS-GacS/A-RsmA/Y/Z is a key regulatory pathway in P. aeruginosa that controls several virulence factors and biofilm formation. We have previously identified a conserved cytoplasmic membrane protein cmpX (PA1775), as a regulator for PA1611 expression. In this study, we demonstrate that cmpX regulates virulence, and controls biofilm formation in P. aeruginosa as well as provide evidence showing that cmpX affects Gac/Rsm pathway, possibly by modulating intra-cellular c-di-GMP levels. A cmpX knockout showed significantly decreased promoter activity of exoS (PA1362) and increased activity of small RNA, RsmY. As compared to the wild-type PAO1, cmpX mutant had elevated intracellular c-di-GMP level as measured indirectly by cdrA (PA4625) activity, as well as increased expression of wspR (PA3702), a c-di-GMP synthase. The transcription of the major outer membrane porin gene oprF (PA1777), and sigma factor sigX (PA1776) was also significantly decreased in the cmpX mutant. Biolog phenotype microarray experiments further indicated that the cmpX knockout mutant had increased sensitivity to membrane detergents and antibiotics such as lauryl sulfobetaine, tobramycin, and vancomycin. These results point to a significant role of cmpX in P. aeruginosa virulence and colonization.

Highlights

1.1 Pseudomonas aeruginosa in chronic diseases Pseudomonas spp. are gram-negative bacteria found ubiquitously within the environment
3.3.5 Corresponding residues in the Histidine Kinases A (HisKA) and histidine kinase-like ATPase (HATPase) domains of RetS are important for PA1611-RetS interaction
Luria Bertani (LB) was used as T3SS non-inducing media; LB supplemented with 5 mM ethylene glycol tetra-acetic acid (EGTA) and 20 mM MgCl2 was used as T3SS-inducing media

Summary

Introduction

1.1 Pseudomonas aeruginosa in chronic diseases Pseudomonas spp. are gram-negative bacteria found ubiquitously within the environment. P. aeruginosa can cause life-threatening nosocomial infections in immunocompromised individuals and those with trauma and severe burns. It a leading cause of infections in ventilator-associated pneumonia and Cystic fibrosis (CF). At initial stages of host infection, the large array of virulence and intrinsic antibiotic resistance mechanisms mediate survival. P. aeruginosa are exposed to the host’s inflammatory responses including oxidative stress followed by treatment with antibiotics. These induce the expression of different sets of genes enabling P. aeruginosa to adapt and switch to persistent and resistant phenotypes while becoming less virulent

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