scholarly journals Activation of Toxin-Antitoxin System Toxins Suppresses Lethality Caused by the Loss of σEin Escherichia coli

2015 ◽  
Vol 197 (14) ◽  
pp. 2316-2324 ◽  
Author(s):  
Yasushi Daimon ◽  
Shin-ichiro Narita ◽  
Yoshinori Akiyama
Keyword(s):  
Escherichia Coli ◽  
Stress Responses ◽  
Ectopic Expression ◽  
Growth Media ◽  
Content Type ◽  
E Coli ◽  
Envelope Stress ◽  
Genes Encoding ◽  
Σ Factor ◽  
Mutant Forms

ABSTRACTσE, an alternative σ factor that governs a major signaling pathway in envelope stress responses in Gram-negative bacteria, is essential for growth ofEscherichia colinot only under stressful conditions, such as elevated temperature, but also under normal laboratory conditions. A mutational inactivation of thehicBgene has been reported to suppress the lethality caused by the loss of σE.hicBencodes the antitoxin of the HicA-HicB toxin-antitoxin (TA) system; overexpression of the HicA toxin, which exhibits mRNA interferase activity, causes cleavage of mRNAs and an arrest of cell growth, while simultaneous expression of HicB neutralizes the toxic effects of overproduced HicA. To date, however, how the loss of HicB rescues the cell lethality in the absence of σEand, more specifically, whether HicA is involved in this process remain unknown. Here we showed that simultaneous disruption ofhicAabolished suppression of the σEessentiality in the absence ofhicB, while ectopic expression of wild-type HicA, but not that of its mutant forms without mRNA interferase activity, restored the suppression. Furthermore, HicA and two other mRNA interferase toxins, HigB and YafQ, suppressed the σEessentiality even in the presence of chromosomally encoded cognate antitoxins when these toxins were overexpressed individually. Interestingly, when the growth media were supplemented with low levels of antibiotics that are known to activate toxins,E. colicells with no suppressor mutations grew independently of σE. Taken together, our results indicate that the activation of TA system toxins can suppress the σEessentiality and affect the extracytoplasmic stress responses.IMPORTANCEσEis an alternative σ factor involved in extracytoplasmic stress responses. Unlike other alternative σ factors, σEis indispensable for the survival ofE. colieven under unstressed conditions, although the exact reason for its essentiality remains unknown. Toxin-antitoxin (TA) systems are widely distributed in prokaryotes and are composed of two adjacent genes, encoding a toxin that exerts harmful effects on the toxin-producing bacterium itself and an antitoxin that neutralizes the cognate toxin. Curiously, it is known that inactivation of an antitoxin rescues the σEessentiality, suggesting a connection between TA systems and σEfunction. We demonstrate here that toxin activation is necessary for this rescue and suggest the possible involvement of TA systems in extracytoplasmic stress responses.

scholarly journals Analysis of Serial Isolates of mcr-1-Positive Escherichia coli Reveals a Highly Active ISApl1 Transposon

2017 ◽  
Vol 61 (5) ◽  
Author(s):  
Erik Snesrud ◽  
Ana C. Ong ◽  
Brendan Corey ◽  
Yoon I. Kwak ◽  
Robert Clifford ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Stress Responses ◽  
Single Copy ◽  
The United States ◽  
Content Type ◽  
E Coli ◽  
Highly Active ◽  
Copy Numbers ◽  
Genes Encoding

ABSTRACT The emergence of a transferable colistin resistance gene (mcr-1) is of global concern. The insertion sequence ISApl1 is a key component in the mobilization of this gene, but its role remains poorly understood. Six Escherichia coli isolates were cultured from the same patient over the course of 1 month in Germany and the United States after a brief hospitalization in Bahrain for an unconnected illness. Four carried mcr-1 as determined by real-time PCR, but two were negative. Two additional mcr-1-negative E. coli isolates were collected during follow-up surveillance 9 months later. All isolates were analyzed by whole-genome sequencing (WGS). WGS revealed that the six initial isolates were composed of two distinct strains: an initial ST-617 E. coli strain harboring mcr-1 and a second, unrelated, mcr-1-negative ST-32 E. coli strain that emerged 2 weeks after hospitalization. Follow-up swabs taken 9 months later were negative for the ST-617 strain, but the mcr-1-negative ST-32 strain was still present. mcr-1 was associated with a single copy of ISApl1, located on a 64.5-kb IncI2 plasmid that shared >95% homology with other mcr-1 IncI2 plasmids. ISApl1 copy numbers ranged from 2 for the first isolate to 6 for the final isolate, but ISApl1 movement was independent of mcr-1. Some movement was accompanied by gene disruption, including the loss of genes encoding proteins involved in stress responses, arginine catabolism, and l-arabinose utilization. These data represent the first comprehensive analysis of ISApl1 movement in serial clinical isolates and reveal that, under certain conditions, ISApl1 is a highly active IS element whose movement may be detrimental to the host cell.

scholarly journals Stress Reduction, Bacterial Style

2017 ◽  
Vol 199 (20) ◽  
Author(s):  
Susan Gottesman
Keyword(s):  
Escherichia Coli ◽  
Stress Reduction ◽  
Stress Responses ◽  
Cell Envelope ◽  
Content Type ◽  
E Coli ◽  
Envelope Stress ◽  
Multiple Cell ◽  
As Stress ◽  
Sigma E

ABSTRACT Bacteria have robust responses to a variety of stresses. In particular, bacteria like Escherichia coli have multiple cell envelope stress responses, and generally we evaluate what these responses are doing by the repair systems they induce. However, probably at least as important in interpreting what is being sensed as stress are the genes that these stress systems downregulate, directly or indirectly. This is discussed here for the Cpx and sigma E systems of E. coli.

scholarly journals Transcriptional Responses of Escherichia coli to a Small-Molecule Inhibitor of LolCDE, an Essential Component of the Lipoprotein Transport Pathway

2016 ◽  
Vol 198 (23) ◽  
pp. 3162-3175 ◽  
Author(s):  
Christian Lorenz ◽  
Thomas J. Dougherty ◽  
Stephen Lory
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Small Molecule ◽  
Stress Responses ◽  
Transport Pathway ◽  
Transcript Levels ◽  
Content Type ◽  
E Coli ◽  
Molecule Inhibitor ◽  
Envelope Stress

ABSTRACTIn Gram-negative bacteria, a dedicated machinery consisting of LolABCDE components targets lipoproteins to the outer membrane. We used a previously identified small-molecule inhibitor of the LolCDE complex ofEscherichia colito assess the global transcriptional consequences of interference with lipoprotein transport. Exposure ofE. colito the LolCDE inhibitor at concentrations leading to minimal and significant growth inhibition, followed by transcriptome sequencing, identified a small group of genes whose transcript levels were decreased and a larger group whose mRNA levels increased 10- to 100-fold compared to those of untreated cells. The majority of the genes whose mRNA concentrations were reduced were part of the flagellar assembly pathway, which contains an essential lipoprotein component. Most of the genes whose transcript levels were elevated encode proteins involved in selected cell stress pathways. Many of these genes are involved with envelope stress responses induced by the mislocalization of outer membrane lipoproteins. Although several of the genes whose RNAs were induced have previously been shown to be associated with the general perturbation of the cell envelope by antibiotics, a small subset was affected only by LolCDE inhibition. Findings from this work suggest that the efficiency of the Lol system function may be coupled to a specific monitoring system, which could be exploited in the development of reporter constructs suitable for use for screening for additional inhibitors of lipoprotein trafficking.IMPORTANCEInhibition of the lipoprotein transport pathway leads toE. colideath and subsequent lysis. Early significant changes in the levels of RNA for a subset of genes identified to be associated with some periplasmic and envelope stress responses were observed. Together these findings suggest that disruption of this key pathway can have a severe impact on balanced outer membrane synthesis sufficient to affect viability.

scholarly journals Heterogeneous and Flexible Transmission ofmcr-1in Hospital-AssociatedEscherichia coli

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Yingbo Shen ◽  
Zuowei Wu ◽  
Yang Wang ◽  
Rong Zhang ◽  
Hong-Wei Zhou ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genomic Analysis ◽  
Multidrug Resistant ◽  
Fluoroquinolone Resistance ◽  
Gram Negative Bacteria ◽  
Colistin Resistance ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Genes Encoding

ABSTRACTThe recent emergence of a transferable colistin resistance mechanism, MCR-1, has gained global attention because of its threat to clinical treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, the possible transmission route ofmcr-1amongEnterobacteriaceaespecies in clinical settings is largely unknown. Here, we present a comprehensive genomic analysis ofEscherichia coliisolates collected in a hospital in Hangzhou, China. We found thatmcr-1-carrying isolates from clinical infections and feces of inpatients and healthy volunteers were genetically diverse and were not closely related phylogenetically, suggesting that clonal expansion is not involved in the spread ofmcr-1. Themcr-1gene was found on either chromosomes or plasmids, but in most of theE. coliisolates,mcr-1was carried on plasmids. The genetic context of the plasmids showed considerable diversity as evidenced by the different functional insertion sequence (IS) elements, toxin-antitoxin (TA) systems, heavy metal resistance determinants, and Rep proteins of broad-host-range plasmids. Additionally, the genomic analysis revealed nosocomial transmission ofmcr-1and the coexistence ofmcr-1with other genes encoding β-lactamases and fluoroquinolone resistance in theE. coliisolates. These findings indicate thatmcr-1is heterogeneously disseminated in both commensal and pathogenic strains ofE. coli, suggest the high flexibility of this gene in its association with diverse genetic backgrounds of the hosts, and provide new insights into the genome epidemiology ofmcr-1among hospital-associatedE. colistrains.IMPORTANCEColistin represents one of the very few available drugs for treating infections caused by extensively multidrug-resistant Gram-negative bacteria. The recently emergentmcr-1colistin resistance gene threatens the clinical utility of colistin and has gained global attention. Howmcr-1spreads in hospital settings remains unknown and was investigated by whole-genome sequencing ofmcr-1-carryingEscherichia coliin this study. The findings revealed extraordinary flexibility ofmcr-1in its spread among genetically diverseE. colihosts and plasmids, nosocomial transmission ofmcr-1-carryingE. coli, and the continuous emergence of novel Inc types of plasmids carryingmcr-1and newmcr-1variants. Additionally,mcr-1was found to be frequently associated with other genes encoding β-lactams and fluoroquinolone resistance. These findings provide important information on the transmission and epidemiology ofmcr-1and are of significant public health importance as the information is expected to facilitate the control of this significant antibiotic resistance threat.

scholarly journals Induction of the Cpx Envelope Stress Pathway Contributes to Escherichia coli Tolerance to Antimicrobial Peptides

2013 ◽  
Vol 79 (24) ◽  
pp. 7770-7779 ◽  
Author(s):  
Bianca Audrain ◽  
Lionel Ferrières ◽  
Amira Zairi ◽  
Guillaume Soubigou ◽  
Curtis Dobson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Polymyxin B ◽  
Genetic Response ◽  
Content Type ◽  
E Coli ◽  
Multiresistant Bacteria ◽  
Envelope Stress ◽  
Stress Pathway

ABSTRACTAntimicrobial peptides produced by multicellular organisms as part of their innate system of defense against microorganisms are currently considered potential alternatives to conventional antibiotics in case of infection by multiresistant bacteria. However, while the mode of action of antimicrobial peptides is relatively well described, resistance mechanisms potentially induced or selected by these peptides are still poorly understood. In this work, we studied the mechanisms of action and resistance potentially induced by ApoEdpL-W, a new antimicrobial peptide derived from human apolipoprotein E. Investigation of the genetic response ofEscherichia coliupon exposure to sublethal concentrations of ApoEdpL-W revealed that this antimicrobial peptide triggers activation of RcsCDB, CpxAR, and σEenvelope stress pathways. This genetic response is not restricted to ApoEdpL-W, since several other antimicrobial peptides, including polymyxin B, melittin, LL-37, and modified S4dermaseptin, also activate severalE. colienvelope stress pathways. Finally, we demonstrate that induction of the CpxAR two-component system directly contributes toE. colitolerance toward ApoEdpL-W, polymyxin B, and melittin. These results therefore show thatE. colisenses and responds to different antimicrobial peptides by activation of the CpxAR pathway. While this study further extends the understanding of the array of peptide-induced stress signaling systems, it also provides insight into the contribution of Cpx envelope stress pathway toE. colitolerance to antimicrobial peptides.

scholarly journals Different Cellular Origins and Functions of Extracellular Proteins from Escherichia coli O157:H7 and O104:H4 as Determined by Comparative Proteomic Analysis

2016 ◽  
Vol 82 (14) ◽  
pp. 4371-4378 ◽  
Author(s):  
Nazrul Islam ◽  
Attila Nagy ◽  
Wesley M. Garrett ◽  
Dan Shelton ◽  
Bret Cooper ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Medium ◽  
Foodborne Pathogen ◽  
The United States ◽  
Extracellular Proteins ◽  
Growth Media ◽  
Environmental Matrices ◽  
Content Type ◽  
E Coli ◽  
Relative Abundances

ABSTRACTExtracellular proteins play important roles in bacterial interactions with the environmental matrices. In this study, we examined the extracellular proteins fromEscherichia coliO157:H7 and O104:H4 by tandem mass spectrometry. We identified 500 and 859 proteins from the growth media ofE. coliO157:H7 and O104:H4, respectively, including 371 proteins common to both strains. Among proteins that were considered specific toE. coliO157:H7 or present at higher relative abundances in O157:H7 medium, most (57 of 65) had secretion signal sequences in their encoding genes. Noticeably, the proteins included locus of enterocyte effacement (LEE) virulence factors, proteins required for peptidyl-lipoprotein accumulation, and proteins involved in iron scavenging. In contrast, a much smaller proportion of proteins (37 of 150) that were considered specific to O104:H4 or presented at higher relative abundances in O104:H4 medium had signals targeting them for secretion. These proteins included Shiga toxin 2 subunit B and O104:H4 signature proteins, including AAF/1 major fimbrial subunit and serine protease autotransporters. Most of the abundant proteins from the growth medium ofE. coliO104:H4 were annotated as having functions in the cytoplasm. We provide evidence that the extensive presence of cytoplasmic proteins inE. coliO104:H4 growth medium was due to biological processes independent of cell lysis, indicating alternative mechanisms for this potent pathogen releasing cytoplasmic contents into the growth milieu, which could play a role in interaction with the environmental matrices, such as pathogenesis and biofilm formation.IMPORTANCEIn this study, we compared the extracellular proteins from two of the most prominent foodborne pathogenicE. coliorganisms that have caused severe outbreaks in the United States and in Europe.E. coliO157:H7 is a well-studied Shiga toxigenic foodborne pathogen of the enterohemorrhagic pathotype that has caused numerous outbreaks associated with various contaminated foods worldwide.E. coliO104:H4 is a newly emerged Shiga toxigenic foodborne pathogen of the enteroaggregative pathotype that gained notoriety for causing one of the most deadly foodborne outbreaks in Europe in 2011. Comparison of proteins in the growth medium revealed significant differences in the compositions of the extracellular proteins for these two pathogens. These differences may provide valuable information regarding the cellular responses of these pathogens to their environment, including cell survival and pathogenesis.

scholarly journals Transcriptome Analysis of Escherichia coli during dGTP Starvation

2016 ◽  
Vol 198 (11) ◽  
pp. 1631-1644 ◽  
Author(s):  
Mark Itsko ◽  
Roel M. Schaaper
Keyword(s):  
Escherichia Coli ◽  
Dna Replication ◽  
Stress Responses ◽  
De Novo ◽  
Replication Stress ◽  
Building Blocks ◽  
Content Type ◽  
Final Cause ◽  
E Coli ◽  
Genome Wide

ABSTRACTOur laboratory recently discovered thatEscherichia colicells starved for the DNA precursor dGTP are killed efficiently (dGTP starvation) in a manner similar to that described for thymineless death (TLD). Conditions for specific dGTP starvation can be achieved by depriving anE. colioptA1 gptstrain of the purine nucleotide precursor hypoxanthine (Hx). To gain insight into the mechanisms underlying dGTP starvation, we conducted genome-wide gene expression analyses of actively growingoptA1 gptcells subjected to hypoxanthine deprivation for increasing periods. The data show that upon Hx withdrawal, theoptA1 gptstrain displays a diminished ability to derepress thede novopurine biosynthesis genes, likely due to internal guanine accumulation. The impairment in fully inducing thepurRregulon may be a contributing factor to the lethality of dGTP starvation. At later time points, and coinciding with cell lethality, strong induction of the SOS response was observed, supporting the concept of replication stress as a final cause of death. No evidence was observed in the starved cells for the participation of other stress responses, including therpoS-mediated global stress response, reinforcing the lack of feedback of replication stress to the global metabolism of the cell. The genome-wide expression data also provide direct evidence for increased genome complexity during dGTP starvation, as a markedly increased gradient was observed for expression of genes located near the replication origin relative to those located toward the replication terminus.IMPORTANCEControl of the supply of the building blocks (deoxynucleoside triphosphates [dNTPs]) for DNA replication is important for ensuring genome integrity and cell viability. When cells are starved specifically for one of the four dNTPs, dGTP, the process of DNA replication is disturbed in a manner that can lead to eventual death. In the present study, we investigated the transcriptional changes in the bacteriumE. coliduring dGTP starvation. The results show increasing DNA replication stress with an increased time of starvation, as evidenced by induction of the bacterial SOS system, as well as a notable lack of induction of other stress responses that could have saved the cells from cell death by slowing down cell growth.

scholarly journals Silver Resistance Genes Are Overrepresented among Escherichia coli Isolates with CTX-M Production

2014 ◽  
Vol 80 (22) ◽  
pp. 6863-6869 ◽  
Author(s):  
Susanne Sütterlin ◽  
Petra Edquist ◽  
Linus Sandegren ◽  
Marlen Adler ◽  
Thomas Tängdén ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Resistance Genes ◽  
Selective Pressure ◽  
Human Origin ◽  
Content Type ◽  
Beta Lactamases ◽  
E Coli ◽  
Genes Encoding ◽  
Extended Spectrum Beta Lactamases ◽  
M 14

ABSTRACTMembers of theEnterobacteriaceaewith extended-spectrum beta-lactamases (ESBLs) of the CTX-M type have disseminated rapidly in recent years and have become a threat to public health. In parallel with the CTX-M type expansion, the consumption and widespread use of silver-containing products has increased. To determine the carriage rates of silver resistance genes in differentEscherichia colipopulations, the presence of three silver resistance genes (silE,silP, andsilS) and genes encoding CTX-M-, TEM-, and SHV-type enzymes were explored inE. coliisolates of human (n= 105) and avian (n= 111) origin. The antibiotic profiles were also determined. Isolates harboring CTX-M genes were further characterized, and phenotypic silver resistance was examined. ThesilEgene was present in 13 of the isolates. All of them were of human origin. Eleven of these isolates harbored ESBLs of the CTX-M type (P= 0.007), and eight of them were typed as CTX-M-15 and three as CTX-M-14. None of thesilE-positive isolates was related to the O25b-ST131 clone, but 10 out of 13 belonged to the ST10 or ST58 complexes. Phenotypic silver resistance (silver nitrate MIC > 512 mg/liter) was observed after silver exposure in 12 of them, and a concomitant reduced susceptibility to piperacillin-tazobactam developed in three. In conclusion, 12% of the humanE. coliisolates but none of the avian isolates harbored silver resistance genes. This indicates another route for or level of silver exposure for humans than that caused by common environmental contamination. SincesilE-positive isolates were significantly more often found in CTX-M-positive isolates, it is possible that silver may exert a selective pressure on CTX-M-producingE. coliisolates.

scholarly journals BaeSR, Involved in Envelope Stress Response, Protects against Lysogenic Conversion by Shiga Toxin 2-Encoding Phages

2015 ◽  
Vol 83 (4) ◽  
pp. 1451-1457 ◽  
Author(s):  
Lejla Imamovic ◽  
Alexandre Martínez-Castillo ◽  
Carmen Benavides ◽  
Maite Muniesa
Keyword(s):  
Stress Responses ◽  
Shiga Toxin ◽  
Phage Infection ◽  
Bacterial Cells ◽  
Content Type ◽  
Signaling Systems ◽  
E Coli ◽  
Envelope Stress ◽  
Lysogenic Conversion

Infection and lysogenic conversion with Shiga toxin-encoding bacteriophages (Stx phages) drive the emergence of new Shiga toxin-producingEscherichia colistrains. Phage attachment to the bacterial surface is the first stage of phage infection. Envelope perturbation causes activation of envelope stress responses in bacterial cells. Although many external factors are known to activate envelope stress responses, the role of these responses in the phage-bacterium interaction remains unexplored. Here, we investigate the link between three envelope signaling systems inE. coli(RcsBC, CpxAR, and BaeSR) and Stx2 phage infection by determining the success of bacterial lysogenic conversion. For this purpose,E. coliDH5α wild-type (WT) and mutant strains lacking RcsBC, CpxAR, or BaeSR signaling systems were incubated with a recombinant Stx2 phage (933W). Notably, the number of lysogens obtained with the BaeSR mutant was 5 log10units higher than with the WT, and the same differences were observed when using 7 different Stx2 phages. To assess whether the membrane receptor used by Stx phages, BamA, was involved in the differences observed,bamAgene expression was monitored by reverse transcription-quantitative PCR (RT-qPCR) in all host strains. A 4-fold-higherbamAexpression level was observed in the BaeSR mutant than in the WT strain, suggesting that differential expression of the receptor used by Stx phages accounted for the increase in the number of lysogenization events. Establishing the link between the role of stress responses and phage infection has important implications for understanding the factors affecting lysogenic conversion, which drives the emergence of new pathogenic clones.

scholarly journals Acetate Exposure Determines the Diauxic Behavior of Escherichia coli during the Glucose-Acetate Transition

2015 ◽  
Vol 197 (19) ◽  
pp. 3173-3181 ◽  
Author(s):  
Brice Enjalbert ◽  
Muriel Cocaign-Bousquet ◽  
Jean-Charles Portais ◽  
Fabien Letisse
Keyword(s):  
Escherichia Coli ◽  
Batch Culture ◽  
Prolonged Exposure ◽  
Growth Parameters ◽  
Metabolic Adaptation ◽  
Growth Stages ◽  
Content Type ◽  
E Coli ◽  
Genes Encoding ◽  
Metabolic Properties

ABSTRACTGrowth ofEscherichia colion glucose in batch culture is accompanied by the excretion of acetate, which is consumed by the cells when glucose is exhausted. This glucose-acetate transition is classically described as a diauxie (two successive growth stages). Here, we investigated the physiological and metabolic properties of cells after glucose exhaustion through the analysis of growth parameters and gene expression. We found thatE. colicells grown on glucose in batch culture produce acetate and consume it after glucose exhaustion but do not grow on acetate. Acetate is catabolized, but key anabolic genes—such as the genes encoding enzymes of the glyoxylate shunt—are not upregulated, hence preventing growth. Both the induction of the latter anabolic genes and growth were observed only after prolonged exposure to low concentrations of acetate and could be accelerated by high acetate concentrations. We postulate that such decoupling between acetate catabolism and acetate anabolism might be an advantage for the survival ofE. coliin the ever-changing environment of the intestine.IMPORTANCEThe glucose-acetate transition is a valuable experimental model for comprehensive investigations of metabolic adaptation and a current paradigm for developing modeling approaches in systems microbiology. Yet, the work reported in our paper demonstrates that the metabolic behavior ofEscherichia coliduring the glucose-acetate transition is much more complex than what has been reported so far. A decoupling between acetate catabolism and acetate anabolism was observed after glucose exhaustion, which has not been reported previously. This phenomenon could represent a strategy for optimal utilization of carbon resources during colonization and persistence ofE. coliin the gut and is also of significant interest for biotechnological applications.

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