Altered Mycobacterium tuberculosis Cell Wall Metabolism and Physiology Associated With RpoB Mutation H526D.

Victoria L Campodónico,Petros C Karakousis,Yu-Min Chuang,Dalin Rifat,Thomas R Ioerger

doi:10.3389/fmicb.2018.00494

Victoria L Campodónico, Petros C Karakousis + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2018.00494

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Abstract

Background: Mycobacterium tuberculosis (Mtb) rpoB mutations are associated with global metabolic remodeling. However, the net effects of rpoB mutations on Mtb physiology, metabolism and function are not completely understood. Based on previous work, we hypothesized that changes in the expression of cell wall molecules in Mtb mutant RpoB 526D lead to changes in cell wall permeability and to altered resistance to environmental stresses and drugs.Methods: The phenotypes of a fully drug-susceptible clinical strain of Mtb and its paired rifampin-monoresistant, RpoB H526D mutant progeny strain were compared.Results: The rpoB mutant showed altered colony morphology, bacillary length and cell wall thickness, which were associated with increased cell wall permeability and susceptibility to the cell wall detergent sodium dodecyl sulfate (SDS) after exposure to nutrient starvation. Relative to the isogenic rifampin-susceptible strain, the RpoB H526D mutant showed altered bacterial cellular metabolic activity and an eightfold increase in susceptibility to the cell-wall acting drug vancomycin.Conclusion: Our data suggest that RpoB mutation H526D is associated with altered cell wall physiology and resistance to cell wall-related stress. These findings are expected to contribute to an improved understanding of the pathogenesis of drug-resistant M. tuberculosis infections.

Highlights

Tuberculosis (TB) remains a major threat to global public health (Lawn and Zumla, 2011), with an estimated 1.7 billion people infected with Mycobacterium tuberculosis (Mtb) globally (WHO, 2017)
RpoB Mutation H526D Is Associated With Slow Growth, Altered Mtb Colony Morphology, Bacillary Length and Cell Wall Thickness
We have demonstrated previously that a laboratory-derived Mtb RpoB H526D mutant had a statistically insignificant fitness cost in nutrient-rich broth, but it was associated with small colony size after exposure to stress conditions (Rifat et al, 2017)

Summary

Introduction

Tuberculosis (TB) remains a major threat to global public health (Lawn and Zumla, 2011), with an estimated 1.7 billion people infected with Mycobacterium tuberculosis (Mtb) globally (WHO, 2017). Lipidomic profiling of rpoB mutant Mtb showed altered concentrations of mycobactin siderophores and acylated sulfoglycolipids (Lahiri et al, 2016), while metabolomics revealed decreased synthesis of various branched-chain fatty acids (du Preez and Loots du, 2012) These cell wall-associated lipids, including PDIM, mycobactin, sulfoglycolipids, and fatty acids, have been implicated in cell wall permeability and virulence (Camacho et al, 2001; Converse et al, 2003; Yeruva et al, 2006; Gebhardt et al, 2007; Gilmore et al, 2012; Reddy et al, 2013; Lahiri et al, 2016; Quigley et al, 2017). We hypothesized that changes in the expression of cell wall molecules in Mtb mutant RpoB 526D lead to changes in cell wall permeability and to altered resistance to environmental stresses and drugs

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Conclusion