Choline catabolism to glycine betaine contributes to Pseudomonas aeruginosa survival during murine lung infection.

Matthew J Wargo

doi:10.1371/journal.pone.0056850

Abstract

Pseudomonas aeruginosa can acquire and metabolize a variety of molecules including choline, an abundant host-derived molecule. In P. aeruginosa, choline is oxidized to glycine betaine which can be used as an osmoprotectant, a sole source of carbon and nitrogen, and as an inducer of the virulence factor, hemolytic phospholipase C (PlcH) via the transcriptional regulator GbdR. The primary objective was to determine the contribution of choline conversion to glycine betaine to P. aeruginosa survival during mouse lung infection. A secondary objective was to gain insight into the relative contributions of the different roles of glycine betaine to P. aeruginosa survival during infection. Using a model of acute murine pneumonia, we determined that deletion of the choline oxidase system (encoded by betBA) decreased P. aeruginosa survival in the mouse lung. Deletion of the glycine betaine demethylase genes (gbcA-B), required for glycine betaine catabolism, did not impact P. aeruginosa survival in the lung. Thus, the defect of the betBA mutant was not due to a requirement for glycine betaine catabolism or dependence on a downstream metabolite. Deletion of betBA decreased the abundance of plcH transcript during infection, which suggested a role for PlcH in the betBA survival defect. To test the contribution of plcH to the betBA mutant phenotype a betBAplcHR double deletion mutant was generated. The betBA and betBAplcHR double mutant had a small but significant survival defect compared to the plcHR single mutant, suggesting that regulation of plcH expression is not the only role for glycine betaine during infection. The conclusion was that choline acquisition and its oxidation to glycine betaine contribute to P. aeruginosa survival in the mouse lung. While defective plcH induction can explain a portion of the betBA mutant phenotype, the exact mechanisms driving the betBA mutant survival defect remain unknown.

Highlights

Pseudomonas aeruginosa is an opportunistic Gram negative pathogen that causes a variety of serious and life threatening infections
P. aeruginosa lung infection is an important component of disease in people with cystic fibrosis and a substantial source of morbidity and mortality in people undergoing mechanical ventilation [1,2]
We are interested in understanding the host-derived small molecules that are important for P. aeruginosa survival during infection in the mammalian lung

Summary

Introduction

Pseudomonas aeruginosa is an opportunistic Gram negative pathogen that causes a variety of serious and life threatening infections. P. aeruginosa lung infection is an important component of disease in people with cystic fibrosis and a substantial source of morbidity and mortality in people undergoing mechanical ventilation [1,2]. In these settings, antibiotic resistance is a rapidly growing problem, there is need for novel therapeutic targets [3,4]. Acquisition and metabolism of small molecules from the host is an important part of establishment and maintenance of infection [5,6,7] These bacterial pathways define a set of potential – yet largely uncharacterized – targets for drug development. We are interested in understanding the host-derived small molecules that are important for P. aeruginosa survival during infection in the mammalian lung

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