Staphylococcus aureusUses the GraXRS Regulatory System To Sense and Adapt to the Acidified Phagolysosome in Macrophages

ABSTRACTMacrophages are critical to innate immunity due to their ability to phagocytose bacteria. The macrophage phagolysosome is a highly acidic organelle with potent antimicrobial properties, yet remarkably, ingestedStaphylococcus aureusreplicates within this niche. Herein we demonstrate thatS. aureusrequires the GraXRS regulatory system for growth within this niche, while the SaeRS and AgrAC two-component regulatory systems and the α-phenol soluble modulins are dispensable. Importantly, we find that it is exposure to acidic pH that is required for optimal growth ofS. aureusinside fully acidified macrophage phagolysosomes. Exposure ofS. aureusto acidic pH evokes GraS signaling, which in turn elicits an adaptive response that endows the bacteria with increased resistance to antimicrobial effectors, such as antimicrobial peptides, encountered inside macrophage phagolysosomes. Notably, pH-dependent induction of antimicrobial peptide resistance inS. aureusrequires the GraS sensor kinase. GraS and MprF, a member of the GraS regulon, play an important role for bacterial survival in the acute stages of systemic infection, where in murine models of infection,S. aureusresides within liver-resident Kupffer cells. We conclude that GraXRS represents a vital regulatory system that functions to allowS. aureusto evade killing, prior to commencement of replication, within host antibacterial immune cells.IMPORTANCES. aureuscan infect any site of the body, including the microbicidal phagolysosome of the macrophage. The ability ofS. aureusto infect diverse niches necessitates that the bacteria be highly adaptable. Here we show thatS. aureusresponds to phagolysosome acidification to evoke changes in gene expression that enable the bacteria to resist phagolysosomal killing and to promote replication. Toxin production is dispensable for this response; however, the bacteria require the sensor kinase GraS, which transduces signals in response to acidic pH. GraS is necessary for phagolysosomal replication and survival ofS. aureusin the acute stage of systemic infection. Disruption of thisS. aureusadaptation would renderS. aureussusceptible to phagocyte restriction.

Download Full-text

The Formation of Streptococcus mutans Persisters Induced by the Quorum-Sensing Peptide Pheromone Is Affected by the LexA Regulator

Journal of Bacteriology ◽

10.1128/jb.02496-14 ◽

2015 ◽

Vol 197 (6) ◽

pp. 1083-1094 ◽

Cited By ~ 23

Author(s):

Vincent Leung ◽

Dragana Ajdic ◽

Stephanie Koyanagi ◽

Céline M. Lévesque

Keyword(s):

Quorum Sensing ◽

Streptococcus Mutans ◽

Bacterial Species ◽

Regulatory System ◽

Bacterial Survival ◽

Chronic Infections ◽

Persister Cells ◽

Gene Encoding ◽

Content Type ◽

Peptide Pheromone

The presence of multidrug-tolerant persister cells within microbial populations has been implicated in the resiliency of bacterial survival against antibiotic treatments and is a major contributing factor in chronic infections. The mechanisms by which these phenotypic variants are formed have been linked to stress response pathways in various bacterial species, but many of these mechanisms remain unclear. We have previously shown that in the cariogenic organismStreptococcus mutans, the quorum-sensing peptide CSP (competence-stimulating peptide) pheromone was a stress-inducible alarmone that triggered an increased formation of multidrug-tolerant persisters. In this study, we characterized SMU.2027, a CSP-inducible gene encoding a LexA ortholog. We showed that in addition to exogenous CSP exposure, stressors, including heat shock, oxidative stress, and ofloxacin antibiotic, were capable of triggering expression oflexAin an autoregulatory manner akin to that of LexA-like transcriptional regulators. We demonstrated the role of LexA and its importance in regulating tolerance toward DNA damage in a noncanonical SOS mechanism. We showed its involvement and regulatory role in the formation of persisters induced by the CSP-ComDE quorum-sensing regulatory system. We further identified key genes involved in sugar and amino acid metabolism, the clustered regularly interspaced short palindromic repeat (CRISPR) system, and autolysin from transcriptomic analyses that contribute to the formation of quorum-sensing-induced persister cells.

Download Full-text

Novel Functions and Signaling Specificity for the GraS Sensor Kinase of Staphylococcus aureus in Response to Acidic pH

Journal of Bacteriology ◽

10.1128/jb.00219-20 ◽

2020 ◽

Vol 202 (22) ◽

Author(s):

Robert C. Kuiack ◽

Ruud A. W. Veldhuizen ◽

Martin J. McGavin

Keyword(s):

Fatty Acids ◽

Staphylococcus Aureus ◽

Cell Surface ◽

Antimicrobial Peptides ◽

Sensor Kinase ◽

Acidic Ph ◽

Content Type ◽

Enhanced Resistance ◽

Secreted Proteases ◽

Arachidonic Acids

ABSTRACT Although the GraS sensor kinase of Staphylococcus aureus is known for the sensing of and resistance to cationic antimicrobial peptides (CAMPs), we recently established that it also signals in response to acidic pH, which is encountered on human skin concurrently with CAMPs, antimicrobial unsaturated free fatty acids (uFFA), and calcium. We therefore evaluated how these environmental signals would affect GraS function and resistance to antimicrobial uFFA. Growth at pH 5.5 promoted increased resistance of S. aureus USA300 to linoleic and arachidonic acids but not palmitoleic or sapienic acid. However, enhanced resistance to these C16:1 uFFA was achieved by supplementing acidic medium with 0.5 mM calcium or subinhibitory CAMPs. Enhanced resistance to uFFA at acidic pH was dependent on GraS and GraS-dependent expression of the lysyl-phosphatidylglycerol synthase enzyme MprF, through a mechanism that did not require the lysyl-transferase function of MprF. In addition to enhanced resistance to antimicrobial uFFA, acidic pH also promoted increased production of secreted proteases in a GraS-dependent manner. During growth at pH 5.5, downstream phenotypes of signaling through GraS, including resistance to uFFA, MprF-dependent addition of positive charge to the cell surface, and increased production of secreted proteases, all occurred independently of acidic amino acids in the extracytoplasmic sensor loop of GraS that were previously found to be required for sensing of CAMPs. Cumulatively, our data indicate that signaling through GraS at acidic pH occurs through a mechanism that is distinct from that described for CAMPs, leading to increased resistance to antimicrobial uFFA and production of secreted proteases. IMPORTANCE Staphylococcus aureus asymptomatically colonizes 30% of humans but is also a leading cause of infectious morbidity and mortality. Since infections are typically initiated by the same strain associated with asymptomatic colonization of the nose or skin, it is important to understand how the microbe can endure exposure to harsh conditions that successfully restrict the growth of other bacteria, including a combination of acidic pH, antimicrobial peptides, and antimicrobial fatty acids. The significance of our research is in showing that acidic pH combined with antimicrobial peptide or environmental calcium can signal through a single membrane sensor protein to promote traits that may aid in survival, including modification of cell surface properties, increased resistance to antimicrobial fatty acids, and enhanced production of secreted proteases.

Download Full-text

Site-Specific Mutation of the Sensor Kinase GraS in Staphylococcus aureus Alters the Adaptive Response to Distinct Cationic Antimicrobial Peptides

Infection and Immunity ◽

10.1128/iai.02480-14 ◽

2014 ◽

Vol 82 (12) ◽

pp. 5336-5345 ◽

Cited By ~ 23

Author(s):

Ambrose L. Cheung ◽

Arnold S. Bayer ◽

Michael R. Yeaman ◽

Yan Q. Xiong ◽

Alan J. Waring ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Antimicrobial Peptides ◽

Target Genes ◽

Regulatory System ◽

Direct Interaction ◽

Sensor Kinase ◽

Target Tissue ◽

Cationic Antimicrobial Peptides ◽

Content Type

ABSTRACTTheStaphylococcus aureustwo-component regulatory system, GraRS, is involved in resistance to killing by distinct host defense cationic antimicrobial peptides (HD-CAPs). It is believed to regulate downstream target genes such asmprFanddltABCDto modify theS. aureussurface charge. However, the detailed mechanism(s) by which the histidine kinase, GraS, senses specific HD-CAPs is not well defined. Here, we studied a well-characterized clinical methicillin-resistantS. aureus(MRSA) strain (MW2), its isogenicgraSdeletion mutant (ΔgraSstrain), a nonameric extracellular loop mutant (ΔEL strain), and four residue-specific ΔEL mutants (D37A, P39A, P39S, and D35G D37G D41G strains). The ΔgraSand ΔEL strains were unable to inducemprFanddltAexpression and, in turn, demonstrated significantly increased susceptibilities to daptomycin, polymyxin B, and two prototypical HD-CAPs (hNP-1 and RP-1). Further, P39A, P39S, and D35G-D37G-D41G ΔEL mutations correlated with moderate increases in HD-CAP susceptibility. Reductions ofmprFanddltAinduction by PMB were also found in the ΔEL mutants, suggesting these residues are pivotal to appropriate activation of the GraS sensor kinase. Importantly, a synthetic exogenous soluble EL mimic of GraS protected the parental MW2 strain against hNP-1- and RP-1-mediated killing, suggesting a direct interaction of the EL with HD-CAPs in GraS activation.In vivo, the ΔgraSand ΔEL strains displayed dramatic reductions in achieved target tissue MRSA counts in an endocarditis model. Taken together, our results provide new insights into potential roles of GraS inS. aureussensing of HD-CAPs to induce adaptive survival responses to these molecules.

Download Full-text

Streptococcus suis Uptakes Carbohydrate Source from Host Glycoproteins by N-glycans Degradation System for Optimal Survival and Full Virulence during Infection

Pathogens ◽

10.3390/pathogens9050387 ◽

2020 ◽

Vol 9 (5) ◽

pp. 387 ◽

Cited By ~ 2

Author(s):

Jiale Ma ◽

Ze Zhang ◽

Zihao Pan ◽

Qiankun Bai ◽

Xiaojun Zhong ◽

...

Keyword(s):

Virulent Strain ◽

Carbon Sources ◽

Systemic Infection ◽

Optimal Growth ◽

Streptococcus Suis ◽

Bacterial Survival ◽

Carbohydrate Source ◽

Virulent Strains ◽

High Mannose ◽

Swine Serum

Infection with the epidemic virulent strain of Streptococcus suis serotype 2 (SS2) can cause septicemia in swine and humans, leading to pneumonia, meningitis and even cytokine storm of Streptococcal toxic shock-like syndrome. Despite some progress concerning the contribution of bacterial adhesion, biofilm, toxicity and stress response to the SS2 systemic infection, the precise mechanism underlying bacterial survival and growth within the host bloodstream remains elusive. Here, we reported the SS2 virulent strains with a more than 20 kb endoSS-related insertion region that showed significantly higher proliferative ability in swine serum than low-virulent strains. Further study identified a complete N-glycans degradation system encoded within this insertion region, and found that both GH92 and EndoSS contribute to bacterial virulence, but that only DndoSS was required for optimal growth of SS2 in host serum. The supplement of hydrolyzed high-mannose-containing glycoprotein by GH92 and EndoSS could completely restore the growth deficiency of endoSS deletion mutant in swine serum. EndoSS only hydrolyzed a part of the model glycoprotein RNase B with high-mannose N-linked glycoforms into a low molecular weight form, and the solo activity of GH92 could not show any changes comparing with the blank control in SDS-PAGE gel. However, complete hydrolyzation was observed under the co-incubation of EndoSS and GH92, suggesting GH92 may degrade the high-mannose arms of N-glycans to generate a substrate for EndoSS. In summary, these findings provide compelling evidences that EndoSS-related N-glycans degradation system may enable SS2 to adapt to host serum-specific availability of carbon sources from glycoforms, and be required for optimal colonization and full virulence during systemic infection.

Download Full-text

User-driven efforts in creating knowledge graph information system

Digital Library Perspectives ◽

10.1108/dlp-12-2019-0043 ◽

2020 ◽

Vol 36 (2) ◽

pp. 97-111

Author(s):

Stanislava Gardasevic

Keyword(s):

Information System ◽

Information Seeking ◽

Information Needs ◽

Resource Discovery ◽

The Body ◽

Knowledge Graph ◽

Structured Interviews ◽

Community Members ◽

Study Objective ◽

Content Type

Purpose This paper presents the results of a qualitative study that involved students of an interdisciplinary PhD program. The study objective was to gather requirements to create a knowledge graph information system. The purpose of this study was to determine information-seeking practices and information needs of this community, to inform the functionalities of a proposed system, intended to help students with relevant resource discovery and decision-making. Design/methodology/approach The study design included semi-structured interviews with eight members of the community, followed by a website usability study with the same student participants. Findings Two main information-seeking styles are recognized and reported through user personas of international and domestic (USA) students. The findings show that the useful information resides within the community and not so much on the program website. Students rely on peer communication, although they report lack of opportunities to connect. Students’ information needs and information seeking are dependent on their progress through the program, as well as their motivation and the projected timeline. Practical implications Considering the current information needs and practices, a knowledge graph hosting both information on social networks and the knowledge produced by the activities of the community members would be useful. By recording data on their activities (for example, collaboration with professors and coursework), students would reveal further useful system functionalities and facilitate transfer of tacit knowledge. Originality/value Aside from the practical value of this research that is directly influencing the design of a system, it contributes to the body of knowledge on interdisciplinary PhD programs.

Download Full-text

Signal Transduction and Regulatory Mechanisms Involved in Control of the σS (RpoS) Subunit of RNA Polymerase

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.66.3.373-395.2002 ◽

2002 ◽

Vol 66 (3) ◽

pp. 373-395 ◽

Cited By ~ 651

Author(s):

Regine Hengge-Aronis

Keyword(s):

Rna Polymerase ◽

Translational Control ◽

Current Knowledge ◽

Response Regulator ◽

Regulatory System ◽

Stress Conditions ◽

Acidic Ph ◽

High Osmolarity ◽

Multiple Signal ◽

Rpos Mrna

SUMMARY The σS (RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little σS, exposure to many different stress conditions results in rapid and strong σS induction. Consequently, transcription of numerous σS-dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular σS level is achieved by rpoS transcriptional and translational control as well as by regulated σS proteolysis, with various stress conditions differentially affecting these levels of σS control. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of σS, which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of σS regulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For σS proteolysis, the response regulator RssB is essential. RssB is a specific direct σS recognition factor, whose affinity for σS is modulated by phosphorylation of its receiver domain. RssB delivers σS to the ClpXP protease, where σS is unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.

Download Full-text

Understanding Semantic Web: a conceptual model

Library Review ◽

10.1108/lr-09-2014-0097 ◽

2015 ◽

Vol 64 (1/2) ◽

pp. 82-100 ◽

Cited By ~ 3

Author(s):

Michael Calaresu ◽

Ali Shiri

Keyword(s):

Semantic Web ◽

Conceptual Model ◽

The Body ◽

Three Dimensional Model ◽

Conceptual Approach ◽

Web Based ◽

Content Type ◽

Software Applications ◽

Web Architecture ◽

The Web

Purpose – The purpose of this article is to explore and conceptualize the Semantic Web as a term that has been widely mentioned in the literature of library and information science. More specifically, its aim is to shed light on the evolution of the Web and to highlight a previously proposed means of attempting to improve automated manipulation of Web-based data in the context of a rapidly expanding base of both users and digital content. Design/methodology/approach – The conceptual analysis presented in this paper adopts a three-dimensional model for the discussion of Semantic Web. The first dimension focuses on Semantic Web’s basic nature, purpose and history, as well as the current state and limitations of modern search systems and related software agents. The second dimension focuses on critical knowledge structures such as taxonomies, thesauri and ontologies which are understood as fundamental elements in the creation of a Semantic Web architecture. In the third dimension, an alternative conceptual model is proposed, one, which unlike more commonly prevalent Semantic Web models, offers a greater emphasis on describing the proposed structure from an interpretive viewpoint, rather than a technical one. This paper adopts an interpretive, historical and conceptual approach to the notion of the Semantic Web by reviewing the literature and by analyzing the developments associated with the Web over the past three decades. It proposes a simplified conceptual model for easy understanding. Findings – The paper provides a conceptual model of the Semantic Web that encompasses four key strata, namely, the body of human users, the body of software applications facilitating creation and consumption of documents, the body of documents themselves and a proposed layer that would improve automated manipulation of Web-based data by the software applications. Research limitations/implications – This paper will facilitate a better conceptual understanding of the Semantic Web, and thereby contribute, in a small way, to the larger body of discourse surrounding it. The conceptual model will provide a reference point for education and research purposes. Originality/value – This paper provides an original analysis of both conceptual and technical aspects of Semantic Web. The proposed conceptual model provides a new perspective on this subject.

Download Full-text

Operations management body of knowledge and its relevance to manufacturing and service organizations

Revista de Gestão ◽

10.1108/rege-03-2018-0049 ◽

2018 ◽

Vol 25 (4) ◽

pp. 373-389 ◽

Cited By ~ 2

Author(s):

Jurandir Peinado ◽

Alexandre Reis Graeml ◽

Fernando Vianna

Keyword(s):

Operations Management ◽

Lean Manufacturing ◽

Process Management ◽

Work Organization ◽

The Body ◽

Service Organizations ◽

Manufacturing Companies ◽

Content Type ◽

Service Companies ◽

Body Of Knowledge

Purpose The purpose of this paper is to assess the differences in importance assigned by manufacturing or service organizations to topics related to operations management and its attendant body of knowledge. Design/methodology/approach The authors did this by cataloguing and analyzing vacancy announcements related to operations management, presented by manufacturing and services companies in major Brazilian human resources websites. Findings The results show that manufacturing companies primarily hire personnel with skills in routine process management, quality management, lean manufacturing, ergonomics and work organization. Service companies generally seek professionals with knowledge and experience in logistics, supply chain management and project management. Research limitations/implications This study presents some limitations that reduce the power of its conclusions. There is some degree of subjectivity in the interpretation of the contents of the analyzed ads. In order to reduce this problem, the authors who did the tabulation of data marked the situations for which there were some doubts about the classification, discussing them with the other author, until they reached a consensus on the best way to classify each one. Originality/value The discussion about the importance assigned by manufacturing and service companies to the topics of operations management is crucial for not only the results obtained, but also to stimulate the debate on topics that comprise or should comprise the body of knowledge of operations management, and the way they are incorporated into business practice. This provides an additional opportunity to reflect on the potential of operations management in supporting business managers now and in the future.

Download Full-text

Natural Disruption of Two Regulatory Networks in Serotype M3 Group A Streptococcus Isolates Contributes to the Virulence Factor Profile of This Hypervirulent Serotype

Infection and Immunity ◽

10.1128/iai.01639-13 ◽

2014 ◽

Vol 82 (5) ◽

pp. 1744-1754 ◽

Cited By ~ 24

Author(s):

Tram N. Cao ◽

Zhuyun Liu ◽

Tran H. Cao ◽

Kathryn J. Pflughoeft ◽

Jeanette Treviño ◽

...

Keyword(s):

Virulence Factor ◽

Regulatory Networks ◽

Molecular Mechanisms ◽

Group A Streptococcus ◽

Regulatory System ◽

Mrna Levels ◽

Bacterial Strains ◽

Content Type ◽

Small Regulatory Rna ◽

Group A

ABSTRACTDespite the public health challenges associated with the emergence of new pathogenic bacterial strains and/or serotypes, there is a dearth of information regarding the molecular mechanisms that drive this variation. Here, we began to address the mechanisms behind serotype-specific variation between serotype M1 and M3 strains of the human pathogenStreptococcus pyogenes(the group AStreptococcus[GAS]). Spatially diverse contemporary clinical serotype M3 isolates were discovered to contain identical inactivating mutations within genes encoding two regulatory systems that control the expression of important virulence factors, including the thrombolytic agent streptokinase, the protease inhibitor-binding protein-G-related α2-macroglobulin-binding (GRAB) protein, and the antiphagocytic hyaluronic acid capsule. Subsequent analysis of a larger collection of isolates determined that M3 GAS, since at least the 1920s, has harbored a 4-bp deletion in thefasCgene of thefasBCAXregulatory system and an inactivating polymorphism in therivRregulator-encoding gene. ThefasCandrivRmutations in M3 isolates directly affect the virulence factor profile of M3 GAS, as evident by a reduction in streptokinase expression and an enhancement of GRAB expression. Complementation of thefasCmutation in M3 GAS significantly enhanced levels of the small regulatory RNA FasX, which in turn enhanced streptokinase expression. Complementation of therivRmutation in M3 GAS restored the regulation ofgrabmRNA abundance but did not alter capsule mRNA levels. While important, thefasCandrivRmutations do not provide a full explanation for why serotype M3 strains are associated with unusually severe invasive infections; thus, further investigation is warranted.

Download Full-text

Global food safety: determinants are Codex standards and WTO's SPS food safety regulations

Journal of Advances in Management Research ◽

10.1108/jamr-01-2013-0007 ◽

2014 ◽

Vol 11 (2) ◽

pp. 176-191 ◽

Cited By ~ 5

Author(s):

Rajneesh Mahajan ◽

Suresh Garg ◽

P.B. Sharma

Keyword(s):

Food Safety ◽

Research Work ◽

The Body ◽

Successful Implementation ◽

Processed Food ◽

Food Sector ◽

Content Type ◽

Safety Regulations ◽

Food Safety Regulations ◽

Global Food

Purpose – The purpose of this paper is to investigate perspective in explaining how global food safety can be created through stringent implementation of Codex and World Trade Organization (WTOs) Sanitary and Phytosanitary food safety regulations and suggests the appropriate food safety system for India. Design/methodology/approach – The study has been deployed a survey questionnaire using a sample of Indian Processed food sector. In order to collect data 1,000 supply chain professional were contacted for seeking their consent to be part of the survey. Whereas total responses collected were 252 from Delhi and NCR, with response rate 25.2 percent. The data collected was empirical tested using descriptive statistics, correlation analysis, regression and ANOVA. Findings – The results and discussions indicate that all the global food safety norms laid down by WTO such as goods manufacturing practices, good hygienic practice, hazard analysis critical control point, has been developed to embody principles of safe food processing sector globally. India has also developed their food safety norms as per laid down principles by WTO. Originality/value – The present research work makes an important contribution to the body of literature on global food safety. The paper has important implications for the processed food sector since it tries to bring out practices which would help in successful implementation of global food safety standards. It is useful for academic food research as well as for processed food corporate.

Download Full-text