DOI: 10.5061/dryad.6hdr7sr12
title: Novel insight into the effects of CPXR on Salmonella enteritidis cells during the chlorhexidine treatment and non-stressful growing conditions

description: The emergence and spread of antimicrobial resistance is a significant
 global challenge. To solve this emerging problem, the discovery of novel
 bacterial cellular targets and the critical pathways associated with
 antimicrobial resistance is urgently needed. In this study, we
 investigated the role of the two most critical extracytoplasmic stress
 response regulators, RpoE and CpxR, on the physiology and susceptibility
 of growing Salmonella enterica serovar Enteritidis cells using the
 polycationic antimicrobial agent, chlorhexidine (CHX). We showed that
 deletion of the cpxR gene significantly increased the susceptibility of
 this organism, whereas deletion of the rpoE gene had no effect on the
 pathogen’s susceptibility to the drug. It has been shown that a lack of
 the CpxR regulator induces multifaceted stress responses not only in the
 envelope but also in the cytosol, further affecting the key biomolecules,
 including DNA, RNA, and proteins. We showed that alterations in cellular
 trafficking and most of the stress responses are associated with a
 dysfunctional CpxR regulator during non-stressful (exponential growth
 phase) conditions, indicating that these physiological changes are
 intrinsically associated with the lack of the CpxR regulator. In contrast,
 induction of type II toxin-antitoxin systems and decrease of abundances of
 enzymes and proteins associated with the recycling of muropeptides and
 resistance to polymixin and cationic antimicrobial peptides were specific
 responses of the ∆cpxR mutant to the CHX treatment. Overall, our study
 provides insight into the effects of CpxR on the physiology of S.
 Enteritidis cells during the exponential growth phase and drug treatment,
 which may point to potential cellular targets for the development of an
 effective antimicrobial agent.    
      
description: Data from the cell growth, determination of MIC of CHX, drug
 treatment assays, complementation study and qRT-PCR represent the average
 of three biological replications. The iTRAQ data related to CHR treatments
 of the wild-type and <i>cpxR</i> mutant represent also the
 averages of three biological replicates, while iTRAQ data relevant to the
 no-CHX treatment represent the averages of two biological
 replicates. The kinetic data for growth rates and drug
 treatment assay were analysed with a two-way analysis of variance (ANOVA),
 with strain and times as factors, followed by Tukey’s <i>post
 hoc</i> test at the 5% level. The residuals were checked to see that
 the assumptions behind the ANOVA model were satisfied. The analyses were
 carried out using Genstat 18<sup>th</sup> edition (VSN
 International, Hemel Hempstead, UK). A value of P &lt; 0.05 was
 considered statistically significant. Gene expression data were analysed
 by <i>t</i>-test. The <i>P</i> values for the
 differences in protein abundance of different samples (wild-type vs
 <i>cpxR</i> mutant and CHX treatment vs no CHX treatment) were
 determined using a two-tailed Student’s
 <i>t</i>-test.
description: These datasets represent the raw data for I) growth curves of the
 wild-type, rpoE and cpxR mutants, II) drug treatment assays, III)
 complementary assay, IV) proteomic iTRAQ data (no drug
 treatment), V) proteomic iTRAQ data (drug treatment) and VI) validation of
 proteomic data. All data are presented in Excel spreadsheet files. Based
 of these data, we created five figures and Tables 2 and 3.