scholarly journals Chaperone-Mediated Stress Sensing in Mycobacterium tuberculosis Enables Fast Activation and Sustained Response

mSystems ◽  
2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Satyajit D. Rao ◽  
Pratik Datta ◽  
Maria Laura Gennaro ◽  
Oleg A. Igoshin
Keyword(s):  
Stress Response ◽  
Surface Stress ◽  
Regulatory Networks ◽  
Content Type ◽  
Chaperone Dnak ◽  
Model Predictions ◽  
Dynamical Properties ◽  
Fast Activation ◽  
Stress Sensing

ABSTRACT Dynamical properties of gene regulatory networks are tuned to ensure bacterial survival. In mycobacteria, the MprAB-σE network responds to the presence of stressors, such as surfactants that cause surface stress. Positive feedback loops in this network were previously predicted to cause hysteresis, i.e., different responses to identical stressor levels for prestressed and unstressed cells. Here, we show that hysteresis does not occur in nonpathogenic Mycobacterium smegmatis but does occur in Mycobacterium tuberculosis. However, the observed rapid temporal response in M. tuberculosis is inconsistent with the model predictions. To reconcile these observations, we implement a recently proposed mechanism for stress sensing, namely, the release of MprB from the inhibitory complex with the chaperone DnaK upon the stress exposure. Using modeling and parameter fitting, we demonstrate that this mechanism can accurately describe the experimental observations. Furthermore, we predict perturbations in DnaK expression that can strongly affect dynamical properties. Experiments with these perturbations agree with model predictions, confirming the role of DnaK in fast and sustained response. IMPORTANCE Gene regulatory networks controlling stress response in mycobacterial species have been linked to persistence switches that enable bacterial dormancy within a host. However, the mechanistic basis of switching and stress sensing is not fully understood. In this paper, combining quantitative experiments and mathematical modeling, we uncover how interactions between two master regulators of stress response—the MprAB two-component system (TCS) and the alternative sigma factor σE—shape the dynamical properties of the surface stress network. The result show hysteresis (history dependence) in the response of the pathogenic bacterium M. tuberculosis to surface stress and lack of hysteresis in nonpathogenic M. smegmatis. Furthermore, to resolve the apparent contradiction between the existence of hysteresis and fast activation of the response, we utilize a recently proposed role of chaperone DnaK in stress sensing. These result leads to a novel system-level understanding of bacterial stress response dynamics.

scholarly journals Chaperone-mediated stress-sensing in Mycobacterium tuberculosis enables fast activation and sustained response

2020 ◽  
Author(s):  
Satyajit D. Rao ◽  
Pratik Datta ◽  
Maria Laura Gennaro ◽  
Oleg A. Igoshin
Keyword(s):  
Stress Response ◽  
Surface Stress ◽  
Regulatory Networks ◽  
Chaperone Dnak ◽  
Model Predictions ◽  
Gene Regulatory ◽  
Dynamical Properties ◽  
Fast Activation ◽  
Stress Sensing

ABSTRACTDynamical properties of gene-regulatory networks are tuned to ensure bacterial survival. In mycobacteria, MprAB-σE network responds to the presence of stressors, such as surfactants causing surface stress. Positive feedback loops in this network were previously predicted to cause hysteresis, i.e. different responses to identical stressor levels for pre-stressed and unstressed cells. Here we show that hysteresis does not occur in non-pathogenic Mycobacterium smegmatis but occurs in Mycobacterium tuberculosis. However, the observed rapid temporal response in M. tuberculosis is inconsistent with the model predictions. To reconcile these observations, we implement a recently proposed mechanism for stress-sensing: the release of MprB from the inhibitory complex with chaperone DnaK upon the stress exposure. Using modeling and parameter fitting, we demonstrate that this mechanism can accurately describe the experimental observations. Furthermore, we predict perturbations in DnaK expression that can strongly affect dynamical properties. Experiments with these perturbations agree with model predictions, confirming the role of DnaK in fast and sustained response.IMPORTANCEGene-regulatory networks controlling stress response in mycobacterial species have been linked to persistence switches enabling the bacterial dormancy within a host. However, the mechanistic basis of switching and stress sensing is not fully understood. In this paper, combining quantitative experiments and mathematical modeling, we uncover how interactions between two master regulators of stress response -- MprAB two-component system and alternative sigma factor σE – shape the dynamical properties of surface-stress network. The result show hysteresis (history dependence) in the response of pathogenic bacteria M. tuberculosis to surface stress and lack of the hysteresis in non-pathogenic M. smegmatis. Furthermore, to resolve the apparent contradiction between the existence of hysteresis and fast activation of the response, we utilize a recently proposed role of chaperone DnaK in stress-sensing. The results leads to a novel system-level understanding of bacterial stress-response dynamics.

scholarly journals Reassessing the Role of the Type II MqsRA Toxin-Antitoxin System in Stress Response and Biofilm Formation: mqsA Is Transcriptionally Uncoupled from mqsR

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Nathan Fraikin ◽  
Clothilde J. Rousseau ◽  
Nathalie Goeders ◽  
Laurence Van Melderen
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Biofilm Formation ◽  
Bile Salts ◽  
Regulatory Networks ◽  
Constitutive Expression ◽  
Toxin Gene ◽  
Global Regulator ◽  
Bacterial Physiology

ABSTRACT Toxin-antitoxin (TA) systems are broadly distributed modules whose biological roles remain mostly unknown. The mqsRA system is a noncanonical TA system in which the toxin and antitoxins genes are organized in operon but with the particularity that the toxin gene precedes that of the antitoxin. This system was shown to regulate global processes such as resistance to bile salts, motility, and biofilm formation. In addition, the MqsA antitoxin was shown to be a master regulator that represses the transcription of the csgD, cspD, and rpoS global regulator genes, thereby displaying a pleiotropic regulatory role. Here, we identified two promoters located in the toxin sequence driving the constitutive expression of mqsA, allowing thereby excess production of the MqsA antitoxin compared to the MqsR toxin. Our results show that both antitoxin-specific and operon promoters are not regulated by stresses such as amino acid starvation, oxidative shock, or bile salts. Moreover, we show that the MqsA antitoxin is not a global regulator as suggested, since the expression of csgD, cspD and rpoS is similar in wild-type and ΔmqsRA mutant strains. Moreover, these two strains behave similarly in terms of biofilm formation and sensitivity to oxidative stress or bile salts. IMPORTANCE There is growing controversy regarding the role of chromosomal toxin-antitoxin systems in bacterial physiology. mqsRA is a peculiar toxin-antitoxin system, as the gene encoding the toxin precedes that of the antitoxin. This system was previously shown to play a role in stress response and biofilm formation. In this work, we identified two promoters specifically driving the constitutive expression of the antitoxin, thereby decoupling the expression of antitoxin from the toxin. We also showed that mqsRA contributes neither to the regulation of biofilm formation nor to the sensitivity to oxidative stress and bile salts. Finally, we were unable to confirm that the MqsA antitoxin is a global regulator. Altogether, our data are ruling out the involvement of the mqsRA system in Escherichia coli regulatory networks.

scholarly journals Adaptations of the Secretome of Candida albicans in Response to Host-Related Environmental Conditions

2015 ◽  
Vol 14 (12) ◽  
pp. 1165-1172 ◽  
Author(s):  
Frans M. Klis ◽  
Stanley Brul
Keyword(s):  
Candida Albicans ◽  
Cell Surface ◽  
Human Body ◽  
Environmental Conditions ◽  
Surface Stress ◽  
Hyphal Growth ◽  
Content Type ◽  
General Response ◽  
Culture Supernatants

ABSTRACTThe wall proteome and the secretome of the fungal pathogenCandida albicanshelp it to thrive in multiple niches of the human body. Mass spectrometry has allowed researchers to study the dynamics of both subproteomes. Here, we discuss some major responses of the secretome to host-related environmental conditions. Three β-1,3-glucan-modifying enzymes, Mp65, Sun41, and Tos1, are consistently found in large amounts in culture supernatants, suggesting that they are needed for construction and expansion of the cell wall β-1,3-glucan layer and thus correlate with growth and might serve as diagnostic biomarkers. The genesENG1,CHT3, andSCW11, which encode an endoglucanase, the major chitinase, and a β-1,3-glucan-modifying enzyme, respectively, are periodically expressed and peak in M/G1. The corresponding protein abundances in the medium correlate with the degree of cell separation during single-yeast-cell, pseudohyphal, and hyphal growth. We also discuss the observation that cells treated with fluconazole, or other agents causing cell surface stress, form pseudohyphal aggregates. Fluconazole-treated cells secrete abundant amounts of the transglucosylase Phr1, which is involved in the accumulation of β-1,3-glucan in biofilms, raising the question whether this is a general response to cell surface stress. Other abundant secretome proteins also contribute to biofilm formation, emphasizing the important role of secretome proteins in this mode of growth. Finally, we discuss the relevance of these observations to therapeutic intervention. Together, these data illustrate thatC. albicansactively adapts its secretome to environmental conditions, thus promoting its survival in widely divergent niches of the human body.

scholarly journals The Alternative Sigma Factor SigB Is Required for the Pathogenicity of Bacillus thuringiensis

2020 ◽  
Vol 202 (21) ◽  
Author(s):  
Stéphanie Henry ◽  
Didier Lereclus ◽  
Leyla Slamti
Keyword(s):  
Life Cycle ◽  
Stress Response ◽  
Bacillus Thuringiensis ◽  
Sigma Factor ◽  
Oral Route ◽  
Alternative Sigma Factor ◽  
Gram Positive ◽  
Content Type ◽  
General Stress Response

ABSTRACT To adapt to changing and potentially hostile environments, bacteria can activate the transcription of genes under the control of alternative sigma factors, such as SigB, a master regulator of the general stress response in several Gram-positive species. Bacillus thuringiensis is a Gram-positive spore-forming invertebrate pathogen whose life cycle includes a variety of environments, including plants and the insect hemocoel or gut. Here, we assessed the role of SigB during the infectious cycle of B. thuringiensis in a Galleria mellonella insect model. We used a fluorescent reporter coupled to flow cytometry and showed that SigB was activated in vivo. We also showed that the pathogenicity of the ΔsigB mutant was severely affected when inoculated via the oral route, suggesting that SigB is critical for B. thuringiensis adaptation to the gut environment of the insect. We could not detect an effect of the sigB deletion on the survival of the bacteria or on their sporulation efficiency in the cadavers. However, the gene encoding the pleiotropic regulator Spo0A was upregulated in the ΔsigB mutant cells during the infectious process. IMPORTANCE Pathogenic bacteria often need to transition between different ecosystems, and their ability to cope with such variations is critical for their survival. Several Gram-positive species have developed an adaptive response mediated by the general stress response alternative sigma factor SigB. In order to understand the ecophysiological role of this regulator in Bacillus thuringiensis, an entomopathogenic bacterium widely used as a biopesticide, we sought to examine the fate of a ΔsigB mutant during its life cycle in the natural setting of an insect larva. This allowed us, in particular, to show that SigB was activated during infection and that it was required for the pathogenicity of B. thuringiensis via the oral route of infection.

scholarly journals Alanyl-tRNA Synthetase Quality Control Prevents Global Dysregulation of the Escherichia coli Proteome

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Paul Kelly ◽  
Nicholas Backes ◽  
Kyle Mohler ◽  
Christopher Buser ◽  
Arundhati Kavoor ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Stress Response ◽  
Genetic Material ◽  
Trna Synthetase ◽  
Content Type ◽  
Beneficial Effects ◽  
Protein Mass ◽  
Protein Mass Spectrometry

ABSTRACT Mechanisms have evolved to prevent errors in replication, transcription, and translation of genetic material, with translational errors occurring most frequently. Errors in protein synthesis can occur at two steps, during tRNA aminoacylation and ribosome decoding. Recent advances in protein mass spectrometry have indicated that previous reports of translational errors have potentially underestimated the frequency of these events, but also that the majority of translational errors occur during ribosomal decoding, suggesting that aminoacylation errors are evolutionarily less tolerated. Despite that interpretation, there is evidence that some aminoacylation errors may be regulated, and thus provide a benefit to the cell, while others are clearly detrimental. Here, we show that while it has been suggested that regulated Thr-to-Ser substitutions may be beneficial, there is a threshold beyond which these errors are detrimental. In contrast, we show that errors mediated by alanyl-tRNA synthetase (AlaRS) are not well tolerated and induce a global stress response that leads to gross perturbation of the Escherichia coli proteome, with potentially catastrophic effects on fitness and viability. Tolerance for Ala mistranslation appears to be much lower than with other translational errors, consistent with previous reports of multiple proofreading mechanisms targeting mischarged tRNAAla. These results demonstrate the essential role of aminoacyl-tRNA proofreading in optimizing cellular fitness and suggest that any potentially beneficial effects of mistranslation may be confined to specific amino acid substitutions. IMPORTANCE Errors in protein synthesis have historically been assumed to be detrimental to the cell. While there are many reports that translational errors are consequential, there is a growing body of evidence that some mistranslation events may be tolerated or even beneficial. Using two models of mistranslation, we compare the direct phenotypic effects of these events in Escherichia coli. This work provides insight into the threshold for tolerance of specific mistranslation events that were previously predicted to be broadly neutral to proteome integrity. Furthermore, these data reveal the effects of mistranslation beyond the general unfolded stress response, leading to global translational reprogramming.

scholarly journals Alternative Sigma Factor RpoE Is Important for Vibrio parahaemolyticus Cell Envelope Stress Response and Intestinal Colonization

2014 ◽  
Vol 82 (9) ◽  
pp. 3667-3677 ◽  
Author(s):  
Brandy Haines-Menges ◽  
W. Brian Whitaker ◽  
E. Fidelma Boyd
Keyword(s):  
Stress Response ◽  
Vibrio Parahaemolyticus ◽  
Response Regulator ◽  
Cell Envelope ◽  
Polymyxin B ◽  
Content Type ◽  
Alternative Sigma Factors ◽  
Envelope Stress

ABSTRACTVibrio parahaemolyticusis a halophile that inhabits brackish waters and a wide range of hosts, including crustaceans, fish, mollusks, and humans. In humans, it is the leading cause of bacterial seafood-borne gastroenteritis. The focus of this work was to determine the role of alternative sigma factors in the stress response ofV. parahaemolyticusRIMD2210633, an O3:K6 pandemic isolate. Bioinformatics identified five putative extracytoplasmic function (ECF) family of alternative sigma factors: VP0055, VP2210, VP2358, VP2578, and VPA1690. ECF factors typically respond to cell wall/cell envelope stress, iron levels, and the oxidation state of the cell. We have demonstrated here that one such sigma factor, VP2578, a homologue of RpoE fromEscherichia coli, is important for survival under a number of cell envelope stress conditions and in gastrointestinal colonization of a streptomycin-treated adult mouse. In this study, we determined that anrpoEdeletion mutant strain BHM2578 compared to the wild type (WT) was significantly more sensitive to polymyxin B, ethanol, and high-temperature stresses. We demonstrated that inin vivocompetition assays between therpoEmutant and the WT marked with the β-galactosidase genelacZ(WBWlacZ), the mutant strain was defective in colonization compared to the WT. In contrast, deletion of therpoSstress response regulator did not affectin vivosurvival. In addition, we examined the role of the outer membrane protein, OmpU, which inV. choleraeis proposed to be the sole activator of RpoE. We found that anompUdeletion mutant was sensitive to bile salt stress but resistant to polymyxin B stress, indicating OmpU is not essential for the cell envelope stress responses or RpoE function. Overall, these data demonstrate that RpoE is a key cell envelope stress response regulator and, similar toE. coli, RpoE may have several factors that stimulate its function.

scholarly journals IdeR, a DtxR Family Iron Response Regulator, Controls Iron Homeostasis, Morphological Differentiation, Secondary Metabolism, and the Oxidative Stress Response inStreptomyces avermitilis

2018 ◽  
Vol 84 (22) ◽  
Author(s):  
Yaqing Cheng ◽  
Renjun Yang ◽  
Mengya Lyu ◽  
Shiwei Wang ◽  
Xingchao Liu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Secondary Metabolism ◽  
Iron Homeostasis ◽  
Morphological Differentiation ◽  
Oxidative Stress Response ◽  
Regulatory Role ◽  
Intracellular Iron ◽  
Content Type

ABSTRACTIron, an essential element for microorganisms, functions as a vital cofactor in a wide variety of key metabolic processes. On the other hand, excess iron may have toxic effects on bacteria by catalyzing the formation of reactive oxygen species through the Fenton reaction. The prevention of iron toxicity requires the precise control of intracellular iron levels in bacteria. Mechanisms of iron homeostasis in the genusStreptomyces(the producers of various antibiotics) are poorly understood.Streptomyces avermitilisis the industrial producer of avermectins, which are potent anthelmintic agents widely used in medicine, agriculture, and animal husbandry. We investigated the regulatory role of IdeR, a DtxR family regulator, inS. avermitilis. In the presence of iron, IdeR binds to a specific palindromic consensus sequence in promoters and regulates 14 targets involved in iron metabolism (e.g., iron acquisition, iron storage, heme metabolism, and Fe-S assembly). IdeR also directly regulates 12 targets involved in other biological processes, including morphological differentiation, secondary metabolism, carbohydrate metabolism, and the tricarboxylic acid (TCA) cycle.ideRtranscription is positively regulated by the peroxide-sensing transcriptional regulator OxyR. A newly constructedideRdeletion mutant (DideR) was found to be less responsive to iron levels and more sensitive to H2O2treatment than the wild-type strain, indicating thatideRis essential for oxidative stress responses. Our findings, taken together, demonstrate that IdeR plays a pleiotropic role in the overall coordination of metabolism inStreptomycesspp. in response to iron levels.IMPORTANCEIron is essential to almost all organisms, but in the presence of oxygen, iron is both poorly available and potentially toxic.Streptomycesspecies are predominantly present in soil where the environment is complex and fluctuating. So far, the mechanism of iron homeostasis inStreptomycesspp. remains to be elucidated. Here, we characterized the regulatory role of IdeR in the avermectin-producing organismS. avermitilis. IdeR maintains intracellular iron levels by regulating genes involved in iron absorption and storage. IdeR also directly regulates morphological differentiation, secondary metabolism, and central metabolism.ideRis under the positive control of OxyR and is indispensable for an efficient response to oxidative stress. This investigation uncovered that IdeR acts as a global regulator coordinating iron homeostasis, morphological differentiation, secondary metabolism, and oxidative stress response inStreptomycesspecies. Elucidation of the pleiotropic regulation function of IdeR provides new insights into the mechanisms of howStreptomycesspp. adapt to the complex environment.

scholarly journals Role of Intracellular Proteases in the Antibiotic Resistance, Motility, and Biofilm Formation of Pseudomonas aeruginosa

2011 ◽  
Vol 56 (2) ◽  
pp. 1128-1132 ◽  
Author(s):  
Lucía Fernández ◽  
Elena B. M. Breidenstein ◽  
Diana Song ◽  
Robert E. W. Hancock
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Biofilm Formation ◽  
Regulatory Networks ◽  
Swarming Motility ◽  
Content Type ◽  
Adverse Conditions ◽  
Related Proteins ◽  
Intracellular Proteases

ABSTRACTPseudomonas aeruginosapossesses complex regulatory networks controlling virulence and survival under adverse conditions, including antibiotic pressure, which are interconnected and share common regulatory proteins. Here, we screen a panel of 13 mutants defective in intracellular proteases and demonstrate that, in addition to the known alterations in Lon and AsrA mutants, mutation of three protease-related proteins PfpI, ClpS, and ClpP differentially affected antibiotic resistance, swarming motility, and biofilm formation.

scholarly journals Divergent Targets of Candida albicans Biofilm Regulator Bcr1In VitroandIn Vivo

2012 ◽  
Vol 11 (7) ◽  
pp. 896-904 ◽  
Author(s):  
Saranna Fanning ◽  
Wenjie Xu ◽  
Norma Solis ◽  
Carol A. Woolford ◽  
Scott G. Filler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Candida Albicans ◽  
Stress Response ◽  
Growth Conditions ◽  
Gene Expression Measurement ◽  
Content Type ◽  
New Genes

ABSTRACTCandida albicansis a causative agent of oropharyngeal candidiasis (OPC), a biofilm-like infection of the oral mucosa. Biofilm formation depends upon theC. albicanstranscription factor Bcr1, and previous studies indicate that Bcr1 is required for OPC in a mouse model of infection. Here we have used a nanoString gene expression measurement platform to elucidate the role of Bcr1 in OPC-related gene expression. We chose for assays a panel of 134 genes that represent a range of morphogenetic and cell cycle functions as well as environmental and stress response pathways. We assayed gene expression in whole infected tongue samples. The results sketch a portrait ofC. albicansgene expression in which numerous stress response pathways are activated during OPC. This one set of experiments identifies 64 new genes with significantly altered RNA levels during OPC, thus increasing substantially the number of known genes in this expression class. Thebcr1Δ/Δ mutant had a much more limited gene expression defect during OPC infection than previously reported forin vitrogrowth conditions. Among major functional Bcr1 targets, we observed thatALS3was Bcr1 dependentin vivowhileHWP1was not. We used null mutants and complemented strains to verify that Bcr1 and Hwp1 are required for OPC infection in this model. The role of Als3 is transient and mild, though significant. Our findings suggest that the versatility ofC. albicansas a pathogen may reflect its ability to persist in the face of multiple stresses and underscore that transcriptional circuitry during infection may be distinct from that detailed duringin vitrogrowth.

scholarly journals RNase III and RNase E Influence Posttranscriptional Regulatory Networks Involved in Virulence Factor Production, Metabolism, and Regulatory RNA Processing in Bordetella pertussis

mSphere ◽  
2021 ◽  
Vol 6 (4) ◽  
Author(s):  
Gyles Ifill ◽  
Travis Blimkie ◽  
Amy Huei-Yi Lee ◽  
George A. Mackie ◽  
Qing Chen ◽  
...  
Keyword(s):  
Bordetella Pertussis ◽  
Regulatory Networks ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Rnase E ◽  
Rnase Iii ◽  
Content Type ◽  
Regulatory Rnas ◽  
Critical Components

Noncoding, regulatory RNAs in bacterial pathogens are critical components required for rapid changes in gene expression profiles. However, little is known about the role of regulatory RNAs in the growth and pathogenesis of Bordetella pertussis .

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