scholarly journals Sharply Tuned pH Response of Genetic Competence Regulation in Streptococcus mutans: a Microfluidic Study of the Environmental Sensitivity ofcomX

2015 ◽  
Vol 81 (16) ◽  
pp. 5622-5631 ◽  
Author(s):  
Minjun Son ◽  
Delaram Ghoreishi ◽  
Sang-Joon Ahn ◽  
Robert A. Burne ◽  
Stephen J. Hagen
Keyword(s):  
Streptococcus Mutans ◽  
Physiological State ◽  
Transient State ◽  
Extracellular Ph ◽  
Genetic Competence ◽  
Content Type ◽  
Ph Response ◽  
Ph Range ◽  
Secreted Peptides

ABSTRACTGenetic competence inStreptococcus mutansis a transient state that is regulated in response to multiple environmental inputs. These include extracellular pH and the concentrations of two secreted peptides, designated CSP (competence-stimulating peptide) and XIP (comX-inducing peptide). The role of environmental cues in regulating competence can be difficult to disentangle from the effects of the organism's physiological state and its chemical modification of its environment. We used microfluidics to control the extracellular environment and study the activation of the key competence genecomX. We find that thecomXpromoter (PcomX) responds to XIP or CSP only when the extracellular pH lies within a narrow window, about 1 pH unit wide, near pH 7. Within this pH range, CSP elicits a strong PcomXresponse from a subpopulation of cells, whereas outside this range the proportion of cells expressingcomXdeclines sharply. Likewise, PcomXis most sensitive to XIP only within a narrow pH window. While previous work suggested thatcomXmay become refractory to CSP or XIP stimulus as cells exit early exponential phase, our microfluidic data show that extracellular pH dominates in determining sensitivity to XIP and CSP. The data are most consistent with an effect of pH on the ComR/ComS system, which has direct control over transcription ofcomXinS. mutans.

scholarly journals Oxidative Stressors Modify the Response of Streptococcus mutans to Its Competence Signal Peptides

2017 ◽  
Vol 83 (22) ◽  
Author(s):  
Matthew De Furio ◽  
Sang Joon Ahn ◽  
Robert A. Burne ◽  
Stephen J. Hagen
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Dental Caries ◽  
Signaling Pathway ◽  
Streptococcus Mutans ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Oral Biofilm ◽  
Genetic Competence ◽  
Content Type

ABSTRACTThe dental caries pathogenStreptococcus mutansis continually exposed to several types of stress in the oral biofilm environment. Oxidative stress generated by reactive oxygen species has a major impact on the establishment, persistence, and virulence ofS. mutans. Here, we combined fluorescent reporter-promoter fusions with single-cell imaging to study the effects of reactive oxygen species on activation of genetic competence inS. mutans. Exposure to paraquat, which generates superoxide anion, produced a qualitatively different effect on activation of expression of the gene for the master competence regulator, ComX, than did treatment with hydrogen peroxide (H2O2), which can yield hydroxyl radical. Paraquat suppressed peptide-mediated induction ofcomXin a progressive and cumulative fashion, whereas the response to H2O2displayed a strong threshold behavior. Low concentrations of H2O2had little effect on induction ofcomXor the bacteriocin genecipB, but expression of these genes declined sharply if extracellular H2O2exceeded a threshold concentration. These effects were not due to decreased reporter gene fluorescence. Two different threshold concentrations were observed in the response to H2O2, depending on the gene promoter that was analyzed and the pathway by which the competence regulon was stimulated. The results show that paraquat and H2O2affect theS. mutanscompetence signaling pathway differently, and that some portions of the competence signaling pathway are more sensitive to oxidative stress than others.IMPORTANCEStreptococcus mutansinhabits the oral biofilm, where it plays an important role in the development of dental caries. Environmental stresses such as oxidative stress influence the growth ofS. mutansand its important virulence-associated behaviors, such as genetic competence.S. mutanscompetence development is a complex behavior that involves two different signaling peptides and can exhibit cell-to-cell heterogeneity. Although oxidative stress is known to influenceS. mutanscompetence, it is not understood how oxidative stress interacts with the peptide signaling or affects heterogeneity. In this study, we used fluorescent reporters to probe the effect of reactive oxygen species on competence signaling at the single-cell level. Our data show that different reactive oxygen species have different effects onS. mutanscompetence, and that some portions of the signaling pathway are more acutely sensitive to oxidative stress than others.

scholarly journals Transcriptional Profiling of the Oral Pathogen Streptococcus mutans in Response to Competence Signaling Peptide XIP

mSystems ◽  
2017 ◽  
Vol 2 (1) ◽  
Author(s):  
Iwona B. Wenderska ◽  
Andrew Latos ◽  
Benjamin Pruitt ◽  
Sara Palmer ◽  
Grace Spatafora ◽  
...  
Keyword(s):  
Gene Expression ◽  
Amino Acid ◽  
Stress Response ◽  
Heat Shock ◽  
Streptococcus Mutans ◽  
Potential Role ◽  
Stringent Response ◽  
Amino Acid Starvation ◽  
Genetic Competence ◽  
Content Type

ABSTRACT Genetic competence provides bacteria with an opportunity to increase genetic diversity or acquire novel traits conferring a survival advantage. In the cariogenic pathogen Streptococcus mutans, DNA transformation is regulated by the competence stimulating peptide XIP (ComX-inducing peptide). The present study utilizes high-throughput RNA sequencing (RNAseq) to provide a greater understanding of how global gene expression patterns change in response to XIP. Overall, our work demonstrates that in S. mutans, XIP signaling induces a response that resembles the stringent response to amino acid starvation. We further identify a novel heat shock-responsive intergenic region with a potential role in competence shutoff. Together, our results provide further evidence that multiple stress response mechanisms are linked through the genetic competence signaling pathway in S. mutans. In the cariogenic Streptococcus mutans, competence development is regulated by the ComRS signaling system comprised of the ComR regulator and the ComS prepeptide to the competence signaling peptide XIP (ComX-inducing peptide). Aside from competence development, XIP signaling has been demonstrated to regulate cell lysis, and recently, the expression of bacteriocins, small antimicrobial peptides used by bacteria to inhibit closely related species. Our study further explores the effect of XIP signaling on the S. mutans transcriptome. RNA sequencing revealed that XIP induction resulted in a global change in gene expression that was consistent with a stress response. An increase in several membrane-bound regulators, including HdrRM and BrsRM, involved in bacteriocin production, and the VicRKX system, involved in acid tolerance and biofilm formation, was observed. Furthermore, global changes in gene expression corresponded to changes observed during the stringent response to amino acid starvation. Effects were also observed on genes involved in sugar transport and carbon catabolite repression and included the levQRST and levDEFG operons. Finally, our work identified a novel heat shock-responsive intergenic region, encoding a small RNA, with a potential role in competence shutoff. IMPORTANCE Genetic competence provides bacteria with an opportunity to increase genetic diversity or acquire novel traits conferring a survival advantage. In the cariogenic pathogen Streptococcus mutans, DNA transformation is regulated by the competence stimulating peptide XIP (ComX-inducing peptide). The present study utilizes high-throughput RNA sequencing (RNAseq) to provide a greater understanding of how global gene expression patterns change in response to XIP. Overall, our work demonstrates that in S. mutans, XIP signaling induces a response that resembles the stringent response to amino acid starvation. We further identify a novel heat shock-responsive intergenic region with a potential role in competence shutoff. Together, our results provide further evidence that multiple stress response mechanisms are linked through the genetic competence signaling pathway in S. mutans.

scholarly journals Sigma S-Dependent Antioxidant Defense Protects Stationary-Phase Escherichia coli against the Bactericidal Antibiotic Gentamicin

2014 ◽  
Vol 58 (10) ◽  
pp. 5964-5975 ◽  
Author(s):  
Jing-Hung Wang ◽  
Rachna Singh ◽  
Michael Benoit ◽  
Mimi Keyhan ◽  
Matthew Sylvester ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Stationary Phase ◽  
Antioxidant Defense ◽  
Physiological State ◽  
Pentose Phosphate ◽  
Phase Cell ◽  
Content Type

ABSTRACTStationary-phase bacteria are important in disease. The σs-regulated general stress response helps them become resistant to disinfectants, but the role of σsin bacterial antibiotic resistance has not been elucidated. Loss of σsrendered stationary-phaseEscherichia colimore sensitive to the bactericidal antibiotic gentamicin (Gm), and proteomic analysis suggested involvement of a weakened antioxidant defense. Use of the psfiAgenetic reporter, 3′-(p-hydroxyphenyl) fluorescein (HPF) dye, and Amplex Red showed that Gm generated more reactive oxygen species (ROS) in the mutant. HPF measurements can be distorted by cell elongation, but Gm did not affect stationary-phase cell dimensions. Coadministration of the antioxidantN-acetyl cysteine (NAC) decreased drug lethality particularly in the mutant, as did Gm treatment under anaerobic conditions that prevent ROS formation. Greater oxidative stress, due to insufficient quenching of endogenous ROS and/or respiration-linked electron leakage, therefore contributed to the greater sensitivity of the mutant; infection by a uropathogenic strain in mice showed this to be the case alsoin vivo. Disruption of antioxidant defense by eliminating the quencher proteins, SodA/SodB and KatE/SodA, or the pentose phosphate pathway proteins, Zwf/Gnd and TalA, which provide NADPH for ROS decomposition, also generated greater oxidative stress and killing by Gm. Thus, besides its established mode of action, Gm also kills stationary-phase bacteria by generating oxidative stress, and targeting the antioxidant defense ofE. colican enhance its efficacy. Relevant aspects of the current controversy on the role of ROS in killing by bactericidal drugs of exponential-phase bacteria, which represent a different physiological state, are discussed.

scholarly journals Expression of an Extracellular Protein (SMU.63) Is Regulated by SprV in Streptococcus mutans

2020 ◽  
Vol 86 (24) ◽  
Author(s):  
Satya Deo Pandey ◽  
Indranil Biswas
Keyword(s):  
Streptococcus Mutans ◽  
Biofilm Formation ◽  
Ion Concentration ◽  
Magnesium Ion ◽  
Genetic Competence ◽  
Ionization Time ◽  
Content Type ◽  
Flight Mass Spectrometry ◽  
Tolerance Response ◽  
Pleiotropic Regulator

ABSTRACT In Streptococcus mutans, SprV (SMU.2137) is a pleiotropic regulator that differentially regulates genes related to competence, mutacin production, biofilm formation, and the stress tolerance response, along with some other pathways. In this study, we established a link between SprV and an ∼67-kDa protein in the culture supernatant of strain UA159 that was later confirmed as SMU.63 by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) analysis. We discovered that SprV downregulates the transcription and translation of SMU.63. We found that the seven amino acids from the C-terminal region of SprV were also crucial for the expression of SMU.63. Deletion of smu.63 led to increased sucrose-independent biofilm formation and competence. The sprV deletion also increased biofilm formation although this could be partially attributed to the downregulation of smu.63. In an smu.63 sprV double mutant, a synergistic effect was observed in biofilm formation in contrast to effects on competence development. We found that low or excess magnesium ion repressed sprV transcription that, in turn, affected the expression of smu.63. As expected, a magnesium ion-dependent effect of competence and biofilm formation was observed in the UA159 strain. We also replicated the results of SMU.63 expression and competence in S. mutans GS5 that encodes both SprV and SMU.63 homologs and found that the GS5 strain behaves similarly to the UA159 strain, indicating that SprV’s effect is strain independent. IMPORTANCE We previously identified a pleiotropic regulator, SprV, in Streptococcus mutans. This regulator appears to be highly conserved among streptococci. Here, we showed that SprV regulates the expression of a secreted protein encoded by SMU.63 in S. mutans. SMU.63 has been known to impact biofilm formation and genetic competence, two important characteristics that help in colonization of the organism. SMU.63 is also unique since it is known to form amyloid fiber. We found that SprV regulates the expression of SMU.63 at both the transcriptional and translational levels. We also found that the expression of SprV is regulated by magnesium ion concentration. Interestingly, both low and high magnesium ion concentrations affected biofilm formation and genetic competence. Since SMU.63 is also highly conserved among streptococci, we hypothesized that SprV will have a similar effect on its expression.

scholarly journals Intercellular Communication via the comX-Inducing Peptide (XIP) of Streptococcus mutans

2017 ◽  
Vol 199 (21) ◽  
Author(s):  
Justin Kaspar ◽  
Simon A. M. Underhill ◽  
Robert C. Shields ◽  
Adrian Reyes ◽  
Suzanne Rosenzweig ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Intercellular Communication ◽  
Stress Responses ◽  
Processing System ◽  
Model Systems ◽  
Extracellular Dna ◽  
Intercellular Signaling ◽  
Genetic Competence ◽  
Content Type ◽  
Communication Signal

ABSTRACT Gram-positive bacteria utilize exported peptides to coordinate genetic and physiological processes required for biofilm formation, stress responses, and ecological competitiveness. One example is activation of natural genetic competence by ComR and the com X -inducing peptide (XIP) in Streptococcus mutans. Although the competence pathway can be activated by the addition of synthetic XIP in defined medium, the hypothesis that XIP is able to function as an intercellular signaling molecule has not been rigorously tested. Coculture model systems were developed that included a “sender” strain that overexpressed the XIP precursor (ComS) and a “responder” strain harboring a green fluorescent protein (GFP) reporter fused to a ComR-activated gene (comX) promoter. The ability of the sender strain to provide a signal to activate GFP expression was monitored at the individual cell and population levels using (i) planktonic culture systems, (ii) cells suspended in an agarose matrix, or (iii) cells growing in biofilms. XIP was shown to be freely diffusible, and XIP signaling between the S. mutans sender and responder strains did not require cell-to-cell contact. The presence of a sucrose-derived exopolysaccharide matrix diminished the efficiency of XIP signaling in biofilms, possibly by affecting the spatial distribution of XIP senders and potential responders. Intercellular signaling was greatly impaired in a strain lacking the primary autolysin, AtlA, and was substantially greater when the sender strain underwent lysis. Collectively, these data provide evidence that S. mutans XIP can indeed function as a peptide signal between cells and highlight the importance of studying signaling with an endogenously produced peptide(s) in populations in various environments and physiologic states. IMPORTANCE The comX-inducing peptide (XIP) of Streptococcus mutans is a key regulatory element in the activation of genetic competence, which allows cells to take up extracellular DNA. XIP has been found in cell culture fluids, and the addition of synthetic XIP to physiologically receptive cells can robustly induce competence gene expression. However, there is a lack of consensus as to whether XIP can function as an intercellular communication signal. Here, we show that XIP indeed signals between cells in S. mutans, but that cell lysis may be a critical factor, as opposed to a dedicated secretion/processing system, in allowing for release of XIP into the environment. The results have important implications in the context of the ecology, virulence, and evolution of a ubiquitous human pathogen and related organisms.

scholarly journals CovR and VicRKX Regulate Transcription of the Collagen Binding Protein Cnm ofStreptococcus mutans

2018 ◽  
Vol 200 (23) ◽  
Author(s):  
Lívia Araújo Alves ◽  
Tridib Ganguly ◽  
Renata O. Mattos-Graner ◽  
Jessica Kajfasz ◽  
Erika N. Harth-Chu ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Bacterial Infections ◽  
Regulatory Region ◽  
Core Gene ◽  
Negative Regulator ◽  
Mobility Shift ◽  
Content Type ◽  
Intracellular Invasion ◽  
Systemic Infections

ABSTRACTCnm is a surface-associated protein present in a subset ofStreptococcus mutansstrains that mediates binding to extracellular matrices, intracellular invasion, and virulence. Here, we showed thatcnmtranscription is controlled by the global regulators CovR and VicRKX.In silicoanalysis identified multiple putative CovR- and VicR-binding motifs in the regulatory region ofcnmas well as in the downstream genepgfS, which is associated with the posttranslational modification of Cnm. Electrophoretic mobility shift assays revealed that CovR and VicR specifically and independently bind to thecnmandpgfSpromoter regions. Quantitative real-time PCR and Western blot analyses of ΔcovRand ΔvicKstrains as well as of a strain overexpressingvicRKXrevealed that CovR functions as a positive regulator ofcnm, whereas VicRKX acts as a negative regulator. In agreement with the role of VicRKX as a repressor, the ΔvicKstrain showed enhanced binding to collagen and laminin and higher intracellular invasion rates. Overexpression ofvicRKXwas associated with decreased rates of intracellular invasion but did not affect collagen or lamin binding activities, suggesting that this system controls additional genes involved in binding to these extracellular matrix proteins. As expected, based on the role of CovR incnmregulation, the ΔcovRstrain showed decreased intracellular invasion rates, but, unexpectedly collagen and laminin binding activities were increased in this mutant strain. Collectively, the results presented here expand the repertoire of virulence-related genes regulated by CovR and VicRKX to include the core genepgfSand the noncore genecnm.IMPORTANCEStreptococcus mutansis a major pathogen associated with dental caries and also implicated in systemic infections, in particular, infective endocarditis. The Cnm adhesin ofS. mutansis an important virulence factor associated with systemic infections and caries severity. Despite its role in virulence, the regulatory mechanisms governingcnmexpression are poorly understood. Here, we describe the identification of two independent regulatory systems controlling the transcription ofcnmand the downstreampgfS-pgfM1-pgfE-pgfM2operon. A better understanding of the mechanisms controlling expression of virulence factors like Cnm can facilitate the development of new strategies to treat bacterial infections.

scholarly journals Genome-Wide Screens Reveal New Gene Products That Influence Genetic Competence in Streptococcus mutans

2017 ◽  
Vol 200 (2) ◽  
Author(s):  
Robert C. Shields ◽  
Greg O'Brien ◽  
Natalie Maricic ◽  
Alexandria Kesterson ◽  
Megan Grace ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Cell Envelope ◽  
Transposon Mutagenesis ◽  
Gene Products ◽  
Dna Uptake ◽  
Novel Genes ◽  
Genetic Competence ◽  
Specific Chemical ◽  
Genetic Traits ◽  
Content Type

ABSTRACTA network of genes and at least two peptide signaling molecules tightly control whenStreptococcus mutansbecomes competent to take up DNA from its environment. Widespread changes in the expression of genes occur whenS. mutansis presented with competence signal peptidesin vitro, including the increased production of the alternative sigma factor, ComX, which activates late competence genes. Still, the way that gene products that are regulated by competence peptides influence DNA uptake and cellular physiology are not well understood. Here, we developed and employed comprehensive transposon mutagenesis of theS. mutansgenome, with a screen to identify mutants that aberrantly expressedcomX, coupled with transposon sequencing (Tn-seq) to gain a more thorough understanding of the factors modulatingcomXexpression and progression to the competent state. The screens effectively identified genes known to affect competence, e.g.,comR,comS,comD,comE,cipB,clpX,rcrR, andciaH, but disclosed an additional 20 genes that were not previously competence associated. The competence phenotypes of mutants were characterized, including by fluorescence microscopy to determine at which stage the mutants were impaired forcomXactivation. Among the novel genes studied were those implicated in cell division, the sensing of cell envelope stress, cell envelope biogenesis, and RNA stability. Our results provide a platform for determining the specific chemical and physical cues that are required for genetic competence inS. mutans, while highlighting the effectiveness of using Tn-seq inS. mutansto discover and study novel biological processes.IMPORTANCEStreptococcus mutansacquires DNA from its environment by becoming genetically competent, a physiologic state triggered by cell-cell communication using secreted peptides. Competence is important for acquiring novel genetic traits and has a strong influence on the expression of virulence-associated traits ofS. mutans. Here, we used transposon mutagenesis and genomic technologies to identify novel genes involved in competence development. In addition to identifying genes previously known to be required forcomXexpression, 20 additional genes were identified and characterized. The findings create opportunities to diminish the pathogenic potential ofS. mutans, while validating technologies that can rapidly advance our understanding of the physiology, biology, and genetics ofS. mutansand related pathogens.

scholarly journals Sterol-Response Pathways Mediate Alkaline Survival in Diverse Fungi

mBio ◽  
2020 ◽  
Vol 11 (3) ◽  
Author(s):  
Hannah E. Brown ◽  
Calla L. Telzrow ◽  
Joseph W. Saelens ◽  
Larissa Fernandes ◽  
J. Andrew Alspaugh
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogens ◽  
Fungal Infections ◽  
Membrane Integrity ◽  
Extracellular Ph ◽  
Alkaline Ph ◽  
Content Type ◽  
Alkaline Environment ◽  
Ph Response ◽  
The Impact

ABSTRACT The ability for cells to maintain homeostasis in the presence of extracellular stress is essential for their survival. Stress adaptations are especially important for microbial pathogens to respond to rapidly changing conditions, such as those encountered during the transition from the environment to the infected host. Many fungal pathogens have acquired the ability to quickly adapt to changes in extracellular pH to promote their survival in the various microenvironments encountered during a host infection. For example, the fungus-specific Rim/Pal alkaline response pathway has been well characterized in many fungal pathogens, including Cryptococcus neoformans. However, alternative mechanisms for sensing and responding to host pH have yet to be extensively studied. Recent observations from a genetic screen suggest that the C. neoformans sterol homeostasis pathway is required for growth at elevated pH. This work explores interactions among mechanisms of membrane homeostasis, alkaline pH tolerance, and Rim pathway activation. We find that the sterol homeostasis pathway is necessary for growth in an alkaline environment and that an elevated pH is sufficient to induce Sre1 activation. This pH-mediated activation of the Sre1 transcription factor is linked to the biosynthesis of ergosterol but is not dependent on Rim pathway signaling, suggesting that these two pathways are responding to alkaline pH independently. Furthermore, we discover that C. neoformans is more susceptible to membrane-targeting antifungals under alkaline conditions, highlighting the impact of microenvironmental pH on the treatment of invasive fungal infections. Together, these findings further connect membrane integrity and composition with the fungal pH response and pathogenesis. IMPORTANCE The work described here further elucidates how microorganisms sense and adapt to changes in their environment to establish infections in the human host. Specifically, we uncover a novel mechanism by which an opportunistic human fungal pathogen, Cryptococcus neoformans, responds to increases in extracellular pH in order to survive and thrive within the relatively alkaline environment of the human lung. This mechanism, which is intimately linked with fungal membrane sterol homeostasis, is independent of the previously well-studied alkaline response Rim pathway. Furthermore, this ergosterol-dependent alkaline pH response is present in Candida albicans, indicating that this mechanism spans diverse fungal species. These results are also relevant for novel antimicrobial drug development as we show that currently used ergosterol-targeting antifungals are more active in alkaline environments.

scholarly journals Different Roles of Membrane Potentials in Electrotaxis and Chemotaxis of Dictyostelium Cells

2011 ◽  
Vol 10 (9) ◽  
pp. 1251-1256 ◽  
Author(s):  
Run-chi Gao ◽  
Xiao-dong Zhang ◽  
Yao-hui Sun ◽  
Yoichiro Kamimura ◽  
Alex Mogilner ◽  
...  
Keyword(s):  
Electric Fields ◽  
Membrane Potentials ◽  
Extracellular Ph ◽  
Acidic Ph ◽  
Alkaline Ph ◽  
Microelectrode Recording ◽  
Random Motility ◽  
Content Type ◽  
Chemotactic Index

ABSTRACT Many types of cells migrate directionally in direct current (DC) electric fields (EFs), a phenomenon termed galvanotaxis or electrotaxis. The directional sensing mechanisms responsible for this response to EFs, however, remain unknown. Exposing cells to an EF causes changes in plasma membrane potentials ( V m ). Exploiting the ability of Dictyostelium cells to tolerate drastic V m changes, we investigated the role of V m in electrotaxis and, in parallel, in chemotaxis. We used three independent factors to control V m : extracellular pH, extracellular [K + ], and electroporation. Changes in V m were monitored with microelectrode recording techniques. Depolarized V m was observed under acidic (pH 5.0) and alkaline (pH 9.0) conditions as well as under higher extracellular [K + ] conditions. Electroporation permeabilized the cell membrane and significantly reduced the V m , which gradually recovered over 40 min. We then recorded the electrotactic behaviors of Dictyostelium cells with a defined V m using these three techniques. The directionality (directedness of electrotaxis) was quantified and compared to that of chemotaxis (chemotactic index). We found that a reduced V m significantly impaired electrotaxis without significantly affecting random motility or chemotaxis. We conclude that extracellular pH, [K + ], and electroporation all significantly affected electrotaxis, which appeared to be mediated by the changes in V m . The initial directional sensing mechanisms for electrotaxis therefore differ from those of chemotaxis and may be mediated by changes in resting V m .

scholarly journals Synergy between Nutritional Immunity and Independent Host Defenses Contributes to the Importance of the MntABC Manganese Transporter duringStaphylococcus aureusInfection

2018 ◽  
Vol 87 (1) ◽  
Author(s):  
Jana N. Radin ◽  
Jamie Zhu ◽  
Erin B. Brazel ◽  
Christopher A. McDevitt ◽  
Thomas E. Kehl-Fie
Keyword(s):  
Multiple Stressors ◽  
Critical Role ◽  
Staphylococcal Infection ◽  
Host Defenses ◽  
Content Type ◽  
Immune Effector ◽  
Nutritional Immunity ◽  
Infection Models ◽  
Ph Range

ABSTRACTDuring infection, the host utilizes a diverse array of processes to combat invaders, including the restriction of availability of essential nutrients such as manganese. Similarly to many other pathogens,Staphylococcus aureuspossesses two manganese importers, MntH and MntABC. Several infection models have revealed a critical role for MntABC during staphylococcal infection. However, culture-based studies have suggested parity between the two transporters when cells are resisting manganese starvation imposed by the manganese binding immune effector calprotectin. In this investigation, initial elemental analysis revealed that MntABC is the primary transporter responsible for obtaining manganese in culture in the presence of calprotectin. MntABC was also necessary to maintain wild-type levels of manganese-dependent superoxide dismutase activity in the presence of calprotectin. Building on this framework, we investigated if MntABC enabledS. aureusto resist the synergistic actions of nutritional immunity and other host defenses. This analysis revealed that MntABC critically contributes to staphylococcal growth whenS. aureusis subjected to manganese limitations and exposed to oxidative stress. This transporter was also important for growth in manganese-limited environments whenS. aureuswas forced to consume glucose as an energy source, which occurs when it encounters nitric oxide. MntABC also expanded the pH range conducive forS. aureusgrowth under conditions of manganese scarcity. Collectively, the data presented in this work provide a robust molecular basis for the crucial role of MntABC in staphylococcal virulence. Further, this work highlights the importance of synergy between host defenses and the necessity of evaluating the contribution of virulence factors to pathogenesis in the presence of multiple stressors.

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