GvmR - A Novel LysR-Type Transcriptional Regulator Involved in Virulence and Primary and Secondary Metabolism of Burkholderia pseudomallei.

Linh Tuan Duong,Jörg Mostertz,Christian Kohler,Falko Hochgräfe,Ivo Steinmetz,Harald Gross,Kristin Eske-Pogodda,Gabriel E Wagner,Sandra Schwarz,Katrin Breitbach

doi:10.3389/fmicb.2018.00935

Abstract

Burkholderia pseudomallei is a soil-dwelling bacterium able to survive not only under adverse environmental conditions, but also within various hosts which can lead to the disease melioidosis. The capability of B. pseudomallei to adapt to environmental changes is facilitated by the large number of regulatory proteins encoded by its genome. Among them are more than 60 uncharacterized LysR-type transcriptional regulators (LTTRs). Here we analyzed a B. pseudomallei mutant harboring a transposon in the gene BPSL0117 annotated as a LTTR, which we named gvmR (globally acting virulence and metabolism regulator). The gvmR mutant displayed a growth defect in minimal medium and macrophages in comparison with the wild type. Moreover, disruption of gvmR rendered B. pseudomallei avirulent in mice indicating a critical role of GvmR in infection. These defects of the mutant were rescued by ectopic expression of gvmR. To identify genes whose expression is modulated by GvmR, global transcriptome analysis of the B. pseudomallei wild type and gvmR mutant was performed using whole genome tiling microarrays. Transcript levels of 190 genes were upregulated and 141 genes were downregulated in the gvmR mutant relative to the wild type. Among the most downregulated genes in the gvmR mutant were important virulence factor genes (T3SS3, T6SS1, and T6SS2), which could explain the virulence defect of the gvmR mutant. In addition, expression of genes related to amino acid synthesis, glyoxylate shunt, iron-sulfur cluster assembly, and syrbactin metabolism (secondary metabolite) was decreased in the mutant. On the other hand, inactivation of GvmR increased expression of genes involved in pyruvate metabolism, ATP synthesis, malleobactin, and porin genes. Quantitative real-time PCR verified the differential expression of 27 selected genes. In summary, our data show that GvmR acts as an activating and repressing global regulator that is required to coordinate expression of a diverse set of metabolic and virulence genes essential for the survival in the animal host and under nutrient limitation.

Highlights

Burkholderia pseudomallei is the causative agent of melioidosis, a frequently fatal infectious disease affecting humans and animals which occurs predominantly in Northern Australia, Southeast Asia, China, and Taiwan
Using global transcriptome analysis we show that BPSL0117 is a pleiotropic global regulator of a wide variety of genes involved in iron and amino acid metabolism, SM, T3SS3 and T6SS1 and T6SS2
For the functional analysis of the B. pseudomallei mutant harboring the Tn5 transposon in the gvmR gene, disruption of gvmR was complemented at a neutral site in the chromosome using the mini-Tn7 system (Choi et al, 2008)

Summary

Introduction

Burkholderia pseudomallei is the causative agent of melioidosis, a frequently fatal infectious disease affecting humans and animals which occurs predominantly in Northern Australia, Southeast Asia, China, and Taiwan. As an environmental pathogen B. pseudomallei is adept at surviving and proliferating in diverse environments such as the soil and mammalian and non-mammalian hosts (Wiersinga et al, 2018). This ability has been ascribed to its large genome and its extensive repertoire of virulence factors such as type 3 secretion systems (T3SS), type 6 secretion systems (T6SS), and regulatory proteins (Holden et al, 2004). The function and regulon of the vast majority of these regulators currently remain unknown

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