Title: The Redox-Sensing Regulator Rex Modulates Central Carbon Metabolism, Stress Tolerance Response and Biofilm Formation by Streptococcus mutans

Abstract

The Rex repressor has been implicated in regulation of central carbon and energy metabolism in Gram-positive bacteria. We have previously shown that Streptococcus mutans, the primary causative agent of dental caries, alters its transcriptome upon Rex-deficiency and renders S. mutans to have increased susceptibility to oxidative stress, aberrations in glucan production, and poor biofilm formation. In this study, we showed that rex in S. mutans is co-transcribed as an operon with downstream guaA, encoding a putative glutamine amidotransferase. Electrophoretic mobility shift assays showed that recombinant Rex bound promoters of target genes avidly and specifically, including those down-regulated in response to Rex-deficiency, and that the ability of recombinant Rex to bind to selected promoters was modulated by NADH and NAD⁺ . Results suggest that Rex in S. mutans can function as an activator in response to intracellular NADH/NAD⁺ level, although the exact binding site for activator Rex remains unclear. Consistent with a role in oxidative stress tolerance, hydrogen peroxide challenge assays showed that the Rex-deficient mutant, TW239, and the Rex/GuaA double mutant, JB314, were more susceptible to hydrogen peroxide killing than the wildtype, UA159. Relative to UA159, JB314 displayed major defects in biofilm formation, with a decrease of more than 50-foldmore » in biomass after 48-hours. Collectively, these results further suggest that Rex in S. mutans regulates fermentation pathways, oxidative stress tolerance, and biofilm formation in response to intracellular NADH/NAD⁺ level. Current effort is being directed to further investigation of the role of GuaA in S. mutans cellular physiology.« less

Authors:

Bitoun, Jacob P. ^[1]; Liao, Sumei ^[1]; Yao, Xin ^[1]; Xie, Gary G. ^[2]; Wen, Zezhang T. ^[1]

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+ Show Author Affiliations

1. Louisiana State University, New Orleans, LA (United States)
2. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Publication Date:

Thu Sep 13 00:00:00 EDT 2012

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); National Institute for Dental and Craniofacial Research

OSTI Identifier:

1627548

Grant/Contract Number:  

AC52-06NA25396; R01 DE19452

Resource Type:

Accepted Manuscript

Journal Name:

PLoS ONE

Additional Journal Information:

Journal Volume: 7; Journal Issue: 9; Journal ID: ISSN 1932-6203

Publisher:

Public Library of Science

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; streptococcus mutans; electrophoretic mobility shift assay; bacterial biofilms; oxidative stress; polymerase chain reaction; biofilms; hydrogen peroxide; nucleotides