scholarly journals Lipopolysaccharide Transport System Links Physiological Roles of σ E and ArcA in the Cell Envelope Biogenesis in Shewanella oneidensis

2021 ◽  
Author(s):  
Peilu Xie ◽  
Huihui Liang ◽  
Jiahao Wang ◽  
Yujia Huang ◽  
Haichun Gao
Keyword(s):  
Cell Envelope ◽  
Critical Role ◽  
Shewanella Oneidensis ◽  
Regulatory System ◽  
Redox Status ◽  
Cellular Respiration ◽  
Bacterial Cells ◽  
Respiratory Enzymes ◽  
Content Type ◽  
Global Regulatory System

Arc is a well-characterized global regulatory system that modulates cellular respiration by responding to changes in the redox status in bacterial cells. In addition to regulating expression of respiratory enzymes, Shewanella oneidensis Arc also plays a critical role in cell envelope integrity.

scholarly journals Distinct Roles of Shewanella oneidensis Thioredoxin in Regulation of Cellular Responses to Hydrogen and Organic Peroxides

2019 ◽  
Vol 85 (21) ◽  
Author(s):  
Xue Feng ◽  
Weining Sun ◽  
Linggen Kong ◽  
Haichun Gao
Keyword(s):  
Oxidative Stress ◽  
Stress Response ◽  
Cellular Response ◽  
Critical Role ◽  
Shewanella Oneidensis ◽  
Redox Status ◽  
Antioxidant Systems ◽  
Organic Peroxides ◽  
Research Model ◽  
Content Type

ABSTRACT The thioredoxin (Trx) and glutaredoxin (Grx) antioxidant systems are deeply involved in bacterial response to oxidative stress, but to date, we know surprisingly little about the roles of these systems in response to reactive oxygen species (ROS) other than hydrogen peroxide (H2O2). In this study, we used Shewanella oneidensis, an environmental bacterium, as a research model to investigate the roles of Trx and Grx in oxidative stress response because it has functionally intertwined ROS responsive regulators OxyR and OhrR. We found that Trx1 is the major thiol/disulfide redox system and that in its absence a Grx system becomes essential under normal conditions. Although overshadowed by Trx1 in the wild type, Trx2 can fully replace Trx1 in physiology when overproduced. Trx1 is required for OxyR to function as a repressor but, more importantly, plays a critical role in the cellular response to organic peroxide (OP) by mediating the redox status of OhrR but not OP scavenger OhrA. While none of the trx and grx genes are OxyR dependent, trxA and trxC are affected by OhrR indirectly. Additional data suggest that depletion of glutathione is likely the cue to trigger induced expression of trxA and trxC. These findings underscore the particular importance of Trx in the bacterial OP stress response. IMPORTANCE The Trx and Grx systems are deeply involved in bacterial responses to H2O2-induced oxidative stress. However, little is known about their roles in response to other ROS, such as organic peroxides (OPs). In this study, we used S. oneidensis as a research model to investigate the interplay between Trx/Grx and OxyR/OhrR. We show that Trxs mediate the redox status of transcriptional OP-responding regulator OhrR. Although none of the trx or grx genes are directly controlled by OxyR or OhrR, expression of trxA and trxC is induced by tert-butyl hydroperoxide (t-BHP). We further show that the trxA and trxC genes respond to effects of glutathione (GSH) depletion rather than oxidation. These findings underscore the particular importance of Trx in the bacterial OP stress response.

scholarly journals Photobacterium damselaesubsp.damselae, a Generalist Pathogen with Unique Virulence Factors and High Genetic Diversity

2018 ◽  
Vol 200 (15) ◽  
Author(s):  
Carlos R. Osorio ◽  
Ana Vences ◽  
Xosé M. Matanza ◽  
Mateus S. Terceti
Keyword(s):  
Genetic Diversity ◽  
Virulence Factors ◽  
Cell Envelope ◽  
Fatal Outcome ◽  
Regulatory System ◽  
Cytolytic Activity ◽  
Conjugative Plasmid ◽  
Marine Animals ◽  
High Genetic Diversity ◽  
Content Type

ABSTRACTPhotobacterium damselaesubsp.damselaecauses vibriosis in a variety of marine animals, including fish species of importance in aquaculture. It also may cause wound infections in humans that can progress to a fatal outcome. Two major virulence factors are encoded within the large conjugative plasmid pPHDD1, the phospholipase D damselysin (Dly) and the pore-forming toxin phobalysin P (PhlyP). The two toxins exert hemolytic and cytolytic activities in a synergistic manner. Even though PhlyP has close homologues in manyVibriospecies, it has unique features that differentiate it from related toxins. Dly phospholipase constitutes a singular trait ofP. damselaesubsp.damselaeamong theVibrionaceae, although related toxins are found in members of theAeromonadaceae. Fish farm outbreaks can also be caused by plasmidless strains. Such observations led to the characterization of two ubiquitous chromosome-encoded toxins with lesser cytolytic activity, the pore forming-toxin phobalysin C (PhlyC) and the phospholipase-hemolysin PlpV. The high genetic diversity of this pathogen deserves special attention, as it has a number of strain-specific features, including the cell envelope polysaccharide synthesis clusters. Fish outbreaks are likely caused by multiclonal populations which contain both plasmidless and pPHDD1-harboring isolates and not by well-adapted clonal complexes. Still, among such genetic heterogeneity, it is feasible to identify conserved weak points in the biology of this bacterium: the two-component regulatory system RstAB (CarSR) was found to be necessary for the maximal production of virulence factors, and its inactivation severely impaired virulence.

scholarly journals Correlation between Mutations inliaFSRof Enterococcus faecium and MIC of Daptomycin: Revisiting Daptomycin Breakpoints

2012 ◽  
Vol 56 (8) ◽  
pp. 4354-4359 ◽  
Author(s):  
Jose M. Munita ◽  
Diana Panesso ◽  
Lorena Diaz ◽  
Truc T. Tran ◽  
Jinnethe Reyes ◽  
...  
Keyword(s):  
Enterococcus Faecium ◽  
Cell Envelope ◽  
Strong Association ◽  
Brain Heart Infusion ◽  
Regulatory System ◽  
Content Type ◽  
Initial Event ◽  
Mueller Hinton ◽  
Envelope Stress ◽  
Mueller Hinton Agar

ABSTRACTMutations inliaFSR, a three-component regulatory system controlling cell-envelope stress response, were recently linked with the emergence of daptomycin (DAP) resistance in enterococci. Our previous work showed that aliaFmutation increased the DAP MIC of a vancomycin-resistantEnterococcus faecalisstrain from 1 to 3 μg/ml (the DAP breakpoint is 4 μg/ml), suggesting that mutations in theliaFSRsystem could be a pivotal initial event in the development of DAP resistance. With the hypothesis that clinical enterococcal isolates with DAP MICs between 3 and 4 μg/ml might harbor mutations inliaFSR, we studied 38Enterococcus faeciumbloodstream isolates, of which 8 had DAP MICs between 3 and 4 μg/ml by Etest in Mueller-Hinton agar. Interestingly, 6 of these 8 isolates had predicted amino acid changes in the LiaFSR system. Moreover, we previously showed that among 6 DAP-resistantE. faeciumisolates (MICs of >4 μg/ml), 5 had mutations inliaFSR. In contrast, none of 16E. faeciumisolates with a DAP MIC of ≤2 μg/ml harbored mutations in this system (P< 0.0001). All but one isolate withliaFSRchanges exhibited DAP MICs of ≥16 μg/ml by Etest using brain heart infusion agar (BHIA), a medium that better supports enterococcal growth. Our findings provide a strong association between DAP MICs within the upper susceptibility range and mutations in theliaFSRsystem. Concomitant susceptibility testing on BHIA may be useful for identifying theseE. faeciumfirst-step mutants. Our results also suggest that the current DAP breakpoint forE. faeciummay need to be reevaluated.

scholarly journals The Twin-Arginine Translocation System Is Important for Stress Resistance and Virulence of Brucella melitensis

2020 ◽  
Vol 88 (11) ◽  
Author(s):  
Xin Yan ◽  
Sen Hu ◽  
Yan Yang ◽  
Da Xu ◽  
Huoming Li ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Brucella Melitensis ◽  
Cell Envelope ◽  
Critical Role ◽  
Sodium Dodecyl ◽  
Methionine Sulfoxide Reductase ◽  
Content Type ◽  
Twin Arginine Translocation ◽  
Tat Pathway

ABSTRACT Brucella, the causative agent of brucellosis, is a stealthy intracellular pathogen that is highly pathogenic to a range of mammals, including humans. The twin-arginine translocation (Tat) pathway transports folded proteins across the cytoplasmic membrane and has been implicated in virulence in many bacterial pathogens. However, the roles of the Tat system and related substrates in Brucella remain unclear. We report here that disruption of Tat increases the sensitivity of Brucella melitensis M28 to the membrane stressor sodium dodecyl sulfate (SDS), indicating cell envelope defects, as well as to EDTA. In addition, mutating Tat renders M28 bacteria more sensitive to oxidative stress caused by H2O2. Further, loss of Tat significantly attenuates B. melitensis infection in murine macrophages ex vivo. Using a mouse model for persistent infection, we demonstrate that Tat is required for full virulence of B. melitensis M28. Genome-wide in silico prediction combined with an in vivo amidase reporter assay indicates that at least 23 proteins are authentic Tat substrates, and they are functionally categorized into solute-binding proteins, oxidoreductases, cell envelope biosynthesis enzymes, and others. A comprehensive deletion study revealed that 6 substrates contribute significantly to Brucella virulence, including an l,d-transpeptidase, an ABC transporter solute-binding protein, and a methionine sulfoxide reductase. Collectively, our work establishes that the Tat pathway plays a critical role in Brucella virulence.

scholarly journals Pseudomonas aeruginosa ExsA Regulates a Metalloprotease, ImpA, That Inhibits Phagocytosis of Macrophages

2019 ◽  
Vol 87 (12) ◽  
Author(s):  
Zhenyang Tian ◽  
Sen Cheng ◽  
Bin Xia ◽  
Yongxin Jin ◽  
Fang Bai ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Critical Role ◽  
Surface Protein ◽  
Host Cells ◽  
Bacterial Cells ◽  
Mobility Shift ◽  
Content Type ◽  
Direct Binding ◽  
Mobility Shift Assay ◽  
Opportunistic Pathogenic

ABSTRACT Pseudomonas aeruginosa is an opportunistic pathogenic bacterium whose type III secretion system (T3SS) plays a critical role in acute infections. Translocation of the T3SS effectors into host cells induces cytotoxicity. In addition, the T3SS promotes the intracellular growth of P. aeruginosa during host infections. The T3SS regulon genes are regulated by an AraC-type regulator, ExsA. In this study, we found that an extracellular metalloprotease encoded by impA (PA0572) is under the regulation of ExsA. An ExsA consensus binding sequence was identified upstream of the impA gene, and direct binding of the site by ExsA was demonstrated via an electrophoretic mobility shift assay. We further demonstrate that secreted ImpA cleaves the macrophage surface protein CD44, which inhibits the phagocytosis of the bacterial cells by macrophages. Combined, our results reveal a novel ExsA-regulated virulence factor that cooperatively inhibits the functions of macrophages with the T3SS.

The impact of artificial intelligence and machine learning on the global economy and its implication for the hospitality sector in India

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sudhanshu Bhushan
Keyword(s):  
Artificial Intelligence ◽  
Machine Learning ◽  
Global Economy ◽  
Regulatory System ◽  
Content Type ◽  
Original Contribution ◽  
Hospitality Sector ◽  
Global Regulatory System ◽  
The Impact ◽  
Practical Implications

Purpose The purpose of this paper is to explore and evaluate the existing and future impact of artificial intelligence (AI) and machine learning on the global economy. It includes viewing the inclusion of AI in different sectors, its impact on industries, the trends of the forerunning companies that are capitalizing on AI and the idea of crystalizing exponential growth while maintaining a balance between the understanding of humans and the subsequent possibilities of AI. Design/methodology/approach This paper is based on secondary research, reviewing literature based on different industries and perspectives. Findings The global potential of AI is exponential; the development of AI should be effective. Globally, we see contrasting views, defining the consequences of AI. Hence, the balance between humans and AI, protocols and a global regulatory system needs to be established to prevent catastrophic results soon. Practical implications The benefits of AI are enormous. The rising incorporation of AI must take into consideration the basic safety fundamentals for a better future. Social implications This paper will enable readers to understand the importance of AI in the global economy, its current involvement in major industries and the subsequent need for balance in technology. Originality/value This conceptual review is by its nature and original contribution and, specifically, an interpretation for India.

Recruitment of the TolA protein to cell constriction sites in Escherichia coli via three separate mechanisms, and a critical role for FtsWI activity in recruitment of both TolA and TolQ.

2021 ◽  
Author(s):  
Cynthia A. Hale ◽  
Logan Persons ◽  
Piet A. J. de Boer
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Cell Envelope ◽  
Critical Role ◽  
Gram Negative Bacteria ◽  
Bacterial Cells ◽  
Future Studies ◽  
E Coli ◽  
Middle Domain ◽  
Fundamental Biological Process

The Tol-Pal system of Gram-negative bacteria helps maintain integrity of the cell envelope and ensures that invagination of the envelope layers during cell fission occurs in a well-coordinated manner. In E. coli , the five Tol-Pal proteins (TolQ, R, A, B and Pal) accumulate at cell constriction sites in a manner that normally requires the activity of the cell constriction initiation protein FtsN. While septal recruitment of TolR, TolB and Pal also requires the presence of TolQ and/or TolA, each of the the latter two can recognize constriction sites independently of the other system proteins. What attracts TolQ or TolA to these sites is unclear. We show that FtsN attracts both proteins in an indirect fashion, and that PBP1A, PBP1B and CpoB are dispensable for their septal recruitment. However, the β-lactam aztreonam readily interferes with septal accumulation of both TolQ and TolA, indicating that FtsN-stimulated production of septal peptidoglycan by the FtsWI synthase is critical to their recruitment. We also discovered that each of TolA's three domains can recognize division sites in a separate fashion. Notably, the middle domain (TolAII) is responsible for directing TolA to constriction sites in the absence of other Tol-Pal proteins and CpoB, while recruitment of TolAI and TolAIII requires TolQ and a combination of TolB, Pal, and CpoB, respectively. Additionally, we describe the construction and use of functional fluorescent sandwich fusions of the ZipA division protein, which should be more broadly valuable in future studies of the E. coli cell division machinery. IMPORTANCE Cell division (cytokinesis) is a fundamental biological process that is incompletely understood for any organism. Division of bacterial cells relies on a ring-like machinery called the septal ring or divisome that assembles along the circumference of the mother cell at the site where constriction will eventually occur. In the well-studied bacterium Escherichia coli , this machinery contains over thirty distinct proteins. We studied how two such proteins, TolA and TolQ, which also play a role in maintaining integrity of the outer-membrane, are recruited to the machinery. We find that TolA can be recruited by three separate mechanisms, and that both proteins rely on the activity of a well-studied cell division enzyme for their recruitment.

scholarly journals A Matter of Timing: Contrasting Effects of Hydrogen Sulfide on Oxidative Stress Response in Shewanella oneidensis

2015 ◽  
Vol 197 (22) ◽  
pp. 3563-3572 ◽  
Author(s):  
Genfu Wu ◽  
Fen Wan ◽  
Huihui Fu ◽  
Ning Li ◽  
Haichun Gao
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Sulfide ◽  
Shewanella Oneidensis ◽  
Inhibitory Effect ◽  
Time Dependent ◽  
Bacterial Cells ◽  
Bacterial Survival ◽  
Intracellular Iron ◽  
Content Type ◽  
Stress Responding

ABSTRACTHydrogen sulfide (H2S), well known for its toxic properties, has recently become a research focus in bacteria, in part because it has been found to prevent oxidative stress caused by treatment with some antibiotics. H2S has the ability to scavenge reactive oxygen species (ROS), thus preventing oxidative stress, but it is also toxic, leading to conflicting reports of its effects in different organisms. Here, withShewanella oneidensisas a model, we report that the effects of H2S on the response to oxidative stress are time dependent. When added simultaneously with H2O2, H2S promoted H2O2toxicity by inactivating catalase, KatB, a heme-containing enzyme involved in H2O2degradation. Such an inhibitory effect may apply to other heme-containing proteins, such as cytochromecbb3oxidase. When H2O2was supplied 20 min or later after the addition of H2S, the oxidative-stress-responding regulator OxyR was activated, resulting in increased resistance to H2O2. The activation of OxyR was likely triggered by the influx of iron, a response to lowered intracellular iron due to the iron-sequestering property of H2S. Given thatShewanellabacteria thrive in redox-stratified environments that have abundant sulfur and iron species, our results imply that H2S is more important for bacterial survival in such environmental niches than previously believed.IMPORTANCEPrevious studies have demonstrated that H2S is either detrimental or beneficial to bacterial cells. While it can act as a growth-inhibiting molecule by damaging DNA and denaturing proteins, it helps cells to combat oxidative stress. Here we report that H2S indeed has these contrasting biological functions and that its effects are time dependent. Immediately after H2S treatment, there is growth inhibition due to damage of heme-containing proteins, at least to catalase and cytochromecoxidase. In contrast, when added a certain time later, H2S confers an enhanced ability to combat oxidative stress by activating the H2O2-responding regulator OxyR. Our data reconcile conflicting observations about the functions of H2S.

scholarly journals The Mechanism behind Bacterial Lipoprotein Release: Phenol-Soluble Modulins Mediate Toll-Like Receptor 2 Activation via Extracellular Vesicle Release from Staphylococcus aureus

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Katja Schlatterer ◽  
Christian Beck ◽  
Dennis Hanzelmann ◽  
Marco Lebtig ◽  
Birgit Fehrenbacher ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cytoplasmic Membrane ◽  
Cell Envelope ◽  
Membrane Vesicles ◽  
Extracellular Vesicle ◽  
Host Cells ◽  
Bacterial Cells ◽  
Toll Like Receptor ◽  
Vesicle Release ◽  
Content Type

ABSTRACT The innate immune system uses Toll-like receptor (TLR) 2 to detect conserved bacterial lipoproteins of invading pathogens. The lipid anchor attaches lipoproteins to the cytoplasmic membrane and prevents their release from the bacterial cell envelope. How bacteria release lipoproteins and how these molecules reach TLR2 remain unknown. Staphylococcus aureus has been described to liberate membrane vesicles. The composition, mode of release, and relevance for microbe-host interaction of such membrane vesicles have remained ambiguous. We recently reported that S. aureus can release lipoproteins only when surfactant-like small peptides, the phenol-soluble modulins (PSMs), are expressed. Here we demonstrate that PSM peptides promote the release of membrane vesicles from the cytoplasmic membrane of S. aureus via an increase in membrane fluidity, and we provide evidence that the bacterial turgor is the driving force for vesicle budding under hypotonic osmotic conditions. Intriguingly, the majority of lipoproteins are released by S. aureus as components of membrane vesicles, and this process depends on surfactant-like molecules such as PSMs. Vesicle disruption at high detergent concentrations promotes the capacity of lipoproteins to activate TLR2. These results reveal that vesicle release by bacterium-derived surfactants is required for TLR2-mediated inflammation. IMPORTANCE Our study highlights the roles of surfactant-like molecules in bacterial inflammation with important implications for the prevention and therapy of inflammatory disorders. It describes a potential pathway for the transfer of hydrophobic bacterial lipoproteins, the major TLR2 agonists, from the cytoplasmic membrane of Gram-positive bacteria to the TLR2 receptor at the surface of host cells. Moreover, our study reveals a molecular mechanism that explains how cytoplasmic and membrane-embedded bacterial proteins can be released by bacterial cells without using any of the typical protein secretion routes, thereby contributing to our understanding of the processes used by bacteria to communicate with host organisms and the environment.

scholarly journals Fate of Mutation Rate Depends onagrLocus Expression during Oxacillin-Mediated Heterogeneous-Homogeneous Selection in Methicillin-Resistant Staphylococcus aureus Clinical Strains

2011 ◽  
Vol 55 (7) ◽  
pp. 3176-3186 ◽  
Author(s):  
Konrad B. Plata ◽  
Roberto R. Rosato ◽  
Adriana E. Rosato
Keyword(s):  
Staphylococcus Aureus ◽  
Mutation Rate ◽  
Selection Process ◽  
Critical Role ◽  
Ectopic Expression ◽  
Regulatory System ◽  
Methicillin Resistant ◽  
Content Type ◽  
Heterogeneous Expression ◽  
Mrsa Strains

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) strains are characterized by a heterogeneous expression of resistance. We have previously shown in clinical oxacillin-susceptible,mecA-positive MRSA strains that selection from a very heterogeneous (HeR) to highly homogeneous (HoR) resistant phenotype was mediated by acquisition of mutations through an oxacillin-induced SOS response. In the present study, we used a spotted DNA microarray to evaluate differential gene expression during HeR-HoR selection and found increased expression of theagrtwo-component regulatory system. We hypothesized that increased expression ofagrrepresents a mechanistically relevant component of this process. We demonstrated that inactivation ofagrduring the HeR-HoR selection process results in a significant increase in mutation rate; these effects were reversed by complementing theagrmutant. Furthermore, we found that extemporal ectopic expression ofagrand, more specifically, RNAII inagr-null mutant HeR cells suppressed mutation frequency and the capacity of these cells to undergo the HeR-HoR selection. These findings sustain the concept that increased expression ofagrduring HeR-HoR selection plays a critical role in regulating the β-lactam-induced increased mutation rate in very heterogeneous MRSA strains. Moreover, they indicate that a temporally controlled increase inagrexpression is required to tightly modulate SOS-mediated mutation rates, which then allows for full expression of oxacillin homogeneous resistance in very heterogeneous clinical MRSA strains.

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