scholarly journals Evidence for the Mycobacterial Mce4 Transporter Being a Multiprotein Complex

2021 ◽  
Vol 203 (10) ◽  
Author(s):  
Laura Rank ◽  
Laura E. Herring ◽  
Miriam Braunstein
Keyword(s):  
Mass Spectrometry ◽  
Abc Transporters ◽  
Mycobacterium Smegmatis ◽  
Cell Envelope ◽  
Cholesterol Transport ◽  
Content Type ◽  
Multiprotein Complexes ◽  
Body Of Knowledge ◽  
Unique Cell ◽  
First Time

ABSTRACT Mycobacteria possess Mce transporters that import lipids and are thought to function analogously to ATP-binding cassette (ABC) transporters. However, whereas ABC transporters import substrates using a single solute-binding protein (SBP) to deliver a substrate to permease proteins in the membrane, mycobacterial Mce transporters have a potential for six SBPs (MceA to MceF) working with a pair of permeases (YrbEA and YrbEB), a cytoplasmic ATPase (MceG), and multiple Mce-associated membrane (Mam) and orphaned Mam (Omam) proteins to transport lipids. In this study, we used the model mycobacterium Mycobacterium smegmatis to study the requirement for individual Mce, Mam, and Omam proteins in Mce4 transport of cholesterol. All of the Mce4 and Mam4 proteins we investigated were required for cholesterol uptake. However, not all Omam proteins, which are encoded by genes outside mce loci, proved to contribute to cholesterol import. OmamA and OmamB were required for cholesterol import, while OmamC, OmamD, OmamE, and OmamF were not. In the absence of any single Mce4, Mam4, or Omam protein that we tested, the abundance of Mce4A and Mce4E declined. This relationship between the levels of Mce4A and Mce4E and these additional proteins suggests a network of interactions that assemble and/or stabilize a multiprotein Mce4 transporter complex. Further support for Mce transporters being multiprotein complexes was obtained by immunoprecipitation-mass spectrometry, in which we identified every single Mce, YrbE, MceG, Mam, and Omam protein with a role in cholesterol transport as associating with Mce4A. This study represents the first time any of these Mce4 transporter proteins has been shown to associate. IMPORTANCE How lipids travel between membranes of diderm bacteria is a challenging mechanistic question because lipids, which are hydrophobic molecules, must traverse a hydrophilic periplasm. This question is even more complex for mycobacteria, which have a unique cell envelope that is highly impermeable to molecules. A growing body of knowledge identifies Mce transporters as lipid importers for mycobacteria. Here, using protein stability experiments and immunoprecipitation-mass spectrometry, we provide evidence for mycobacterial Mce transporters existing as multiprotein complexes.

scholarly journals Evolution of Mycolic Acid Biosynthesis Genes and Their Regulation during Starvation in Mycobacterium tuberculosis

2015 ◽  
Vol 197 (24) ◽  
pp. 3797-3811 ◽  
Author(s):  
Stevie Jamet ◽  
Yves Quentin ◽  
Coralie Coudray ◽  
Pauline Texier ◽  
Françoise Laval ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Outer Membrane ◽  
Cell Envelope ◽  
Stringent Response ◽  
Mycolic Acid ◽  
Content Type ◽  
New Targets ◽  
Key Enzyme ◽  
Unique Cell ◽  
Translational Apparatus

ABSTRACTMycobacterium tuberculosis, the etiological agent of tuberculosis, is a Gram-positive bacterium with a unique cell envelope composed of an essential outer membrane. Mycolic acids, which are very-long-chain (up to C100) fatty acids, are the major components of this mycomembrane. The enzymatic pathways involved in the biosynthesis and transport of mycolates are fairly well documented and are the targets of the major antituberculous drugs. In contrast, only fragmented information is available on the expression and regulation of the biosynthesis genes. In this study, we report that thehadA,hadB, andhadCgenes, which code for the mycolate biosynthesis dehydratase enzymes, are coexpressed with three genes that encode proteins of the translational apparatus. Consistent with the well-established control of the translation potential by nutrient availability, starvation leads to downregulation of thehadABCgenes along with most of the genes required for the synthesis, modification, and transport of mycolates. The downregulation of a subset of the biosynthesis genes is partially dependent on RelMtb, the key enzyme of the stringent response. We also report the phylogenetic evolution scenario that has shaped the current genetic organization, characterized by the coregulation of thehadABCoperon with genes of the translational apparatus and with genes required for the modification of the mycolates.IMPORTANCEMycobacterium tuberculosisinfects one-third of the human population worldwide, and despite the available therapeutic arsenal, it continues to kill millions of people each year. There is therefore an urgent need to identify new targets and develop a better understanding of how the bacterium is adapting itself to host defenses during infection. A prerequisite of this understanding is knowledge of how this adaptive skill has been implanted by evolution. Nutrient scarcity is an environmental condition the bacterium has to cope with during infection. In many bacteria, adaptation to starvation relies partly on the stringent response.M. tuberculosis's unique outer membrane layer, the mycomembrane, is crucial for its viability and virulence. Despite its being the target of the major antituberculosis drugs, only scattered information exists on how the genes required for biosynthesis of the mycomembrane are expressed and regulated during starvation. This work has addressed this issue as a step toward the identification of new targets in the fight againstM. tuberculosis.

scholarly journals Iron Deprivation Affects Drug Susceptibilities of Mycobacteria Targeting Membrane Integrity

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Rahul Pal ◽  
Saif Hameed ◽  
Zeeshan Fatima
Keyword(s):  
Mycobacterium Smegmatis ◽  
Cell Envelope ◽  
Membrane Integrity ◽  
Genotoxic Stress ◽  
Drug Susceptibility ◽  
First Line ◽  
Antitubercular Drugs ◽  
Iron Deprivation ◽  
Cellular Iron ◽  
First Time

Multidrug resistance (MDR) acquired byMycobacterium tuberculosis(MTB) through continuous deployment of antitubercular drugs warrants immediate search for novel targets and mechanisms. The ability of MTB to sense and become accustomed to changes in the host is essential for survival and confers the basis of infection. A crucial condition that MTB must surmount is iron limitation, during the establishment of infection, since iron is required by both bacteria and humans. This study focuses on how iron deprivation affects drug susceptibilities of known anti-TB drugs inMycobacterium smegmatis, a “surrogate of MTB.” We showed that iron deprivation leads to enhanced potency of most commonly used first line anti-TB drugs that could be reverted upon iron supplementation. We explored that membrane homeostasis is disrupted upon iron deprivation as revealed by enhanced membrane permeability and hypersensitivity to membrane perturbing agent leading to increased passive diffusion of drug and TEM images showing detectable differences in cell envelope thickness. Furthermore, iron seems to be indispensable to sustain genotoxic stress suggesting its possible role in DNA repair machinery. Taken together, we for the first time established a link between cellular iron and drug susceptibility of mycobacteria suggesting iron as novel determinant to combat MDR.

Performance of adaptive np-chart with estimated parameter

2016 ◽  
Vol 33 (6) ◽  
pp. 769-791 ◽  
Author(s):  
S. Mohammad Hashemian ◽  
Rassoul Noorossana ◽  
Ali Keyvandarian ◽  
Maryam Shekary A.
Keyword(s):  
Phase I ◽  
Control Chart ◽  
Performance Measures ◽  
Control Charts ◽  
Process Parameter ◽  
The Body ◽  
Content Type ◽  
Average Time To Signal ◽  
Body Of Knowledge ◽  
First Time

Purpose – The purpose of this paper is to compare the performances of np-VP control chart with estimated parameter to the np-VP control chart with known parameter using average time-to-signal (ATS), standard deviation of the time-to-signal (SDTS), and average number of observations to signal (ANOS) as performance measures. Design/methodology/approach – The approach used in this study is probabilistic in which the expected values of performance measures are calculated using probabilities of different estimators used to estimate process parameter. Findings – Numerical results indicate different performances for the np-VP control chart in known and estimated parameter cases. It is obvious that when process parameter is not known and is estimated using Phase I data, the chart does not perform as user expects. To tackle this issue, optimal Phase I estimation scenarios are recommended to obtain the best performance from the chart in the parameter estimation case in terms of performance measures. Practical implications – This research adds to the body of knowledge in quality control of process monitoring systems. This paper may be of particular interest to practitioners of quality systems in factories where products are monitored to reduce the number of defectives and np chart parameter needs to be estimated. Originality/value – The originality of this paper lies within the context in which an adaptive np control chart is studied and the process parameter unlike previous studies is assumed unknown. Although other types of control charts have been studied when process parameter is unknown but this is the first time that adaptive np chart performance with estimated process parameter is studied.

scholarly journals KpnEF, a New Member of the Klebsiella pneumoniae Cell Envelope Stress Response Regulon, Is an SMR-Type Efflux Pump Involved in Broad-Spectrum Antimicrobial Resistance

2013 ◽  
Vol 57 (9) ◽  
pp. 4449-4462 ◽  
Author(s):  
Vijaya Bharathi Srinivasan ◽  
Govindan Rajamohan
Keyword(s):  
Klebsiella Pneumoniae ◽  
Efflux Pump ◽  
Cell Envelope ◽  
Sodium Dodecyl ◽  
Multidrug Resistant ◽  
Content Type ◽  
Enhanced Sensitivity ◽  
Envelope Stress ◽  
Phenotype Analysis ◽  
First Time

ABSTRACTKlebsiella pneumoniaehas been frequently associated with nosocomial infections. Efflux systems are ubiquitous transporters that also function in drug resistance. Genome analysis ofK. pneumoniaestrain NTUH-K2044 revealed the presence of ∼15 putative drug efflux systems. We discuss here for the first time the characterization of a putative SMR-type efflux pump, anebrABhomolog (denoted here askpnEF) with respect toKlebsiellaphysiology and the multidrug-resistant phenotype. Analysis of hypermucoviscosity revealed direct involvement ofkpnEFin capsule synthesis. The ΔkpnEFmutant displayed higher sensitivity to hyperosmotic (∼2.8-fold) and high bile (∼4.0-fold) concentrations. Mutation inkpnEFresulted in increased susceptibility to cefepime, ceftriaxone, colistin, erythromycin, rifampin, tetracycline, and streptomycin; mutated strains changed from being resistant to being susceptible, and the resistance was restored upon complementation. The ΔkpnEFmutant displayed enhanced sensitivity toward structurally related compounds such as sodium dodecyl sulfate, deoxycholate, and dyes, including clinically relevant disinfectants such as benzalkonium chloride, chlorhexidine, and triclosan. The prevalence ofkpnEFin clinical strains broadens the diversity of antibiotic resistance inK. pneumoniae. Experimental evidence of CpxR binding to the efflux pump promoter and quantification of its expression in acpxARmutant background demonstratedkpnEFto be a member of the Cpx regulon. This study helps to elucidate the unprecedented biological functions of the SMR-type efflux pump inKlebsiellaspp.

Challenges of implementing lean construction in the construction industry in Bangladesh

2019 ◽  
Vol 9 (2) ◽  
pp. 174-207 ◽  
Author(s):  
Shakil Ahmed ◽  
Md Habibur Rahman Sobuz
Keyword(s):  
Construction Industry ◽  
Economic Status ◽  
Skills Training ◽  
Lean Construction ◽  
The Body ◽  
Content Type ◽  
Body Of Knowledge ◽  
Construction Organizations ◽  
Management Commitment ◽  
First Time

Purpose Construction management is ameliorated by the lean construction concept in many direct and indirect ways to reduce waste of construction process and improve the value. The purpose of this paper is to identify the challenges of the implementation of lean construction in the Bangladeshi construction industry and to prioritize these factors that constitute these challenges. Design/methodology/approach A comprehensive literature review was used for shorting the global challenges of implementing lean construction. Subsequently, these challenges were incorporated into a structured questionnaire for survey. A total of 164 valid responses were collected from Bangladeshi construction practitioners involved in different types of construction organizations. The results were analyzed using the Relative Important Index (RII) and Mann–Whitney U test. Findings The findings revealed 41 challenges of lean construction implementation in the Bangladeshi construction industry. The highest ranking challenges are the lack of awareness about lean construction, lack of skills, training and lean techniques, unwillingness to change the existing culture, lack of management commitment, fragmented and cyclic nature of the construction project and unavailing communication between all project participants. The study also discusses some universally applicable solutions to overcome these challenges. Originality/value By the findings of this study, the Bangladeshi construction industry could get a new insight into the challenges of implementing lean construction. It could play a very important part in the body of knowledge, as it reveals the challenges of implementing lean construction for the first time with the socio-economic context of Bangladesh. Exploring the findings, the study could help the stakeholders, companies, academician, researchers and government to focus their effort and resources on the significantly appropriate issues. Furthermore, this study may beneficial to those developing countries especially in South Asia, who have shared the same socio-economic status with Bangladesh.

scholarly journals Characterization of a Regulatory Network of Peptide Antibiotic Detoxification Modules in Lactobacillus casei BL23

2013 ◽  
Vol 79 (10) ◽  
pp. 3160-3170 ◽  
Author(s):  
Ainhoa Revilla-Guarinos ◽  
Susanne Gebhard ◽  
Cristina Alcántara ◽  
Anna Staroń ◽  
Thorsten Mascher ◽  
...  
Keyword(s):  
Abc Transporter ◽  
Abc Transporters ◽  
Lactobacillus Casei ◽  
Cell Envelope ◽  
Peptide Antibiotic ◽  
Content Type ◽  
Component Systems ◽  
Two Component Systems ◽  
Intracellular Changes

ABSTRACTTwo-component systems (TCS) are major signal transduction pathways that allow bacteria to detect and respond to environmental and intracellular changes. A group of TCS has been shown to be involved in the response against antimicrobial peptides (AMPs). These TCS are characterized by the possession of intramembrane-sensing histidine kinases, and they are usually associated with ABC transporters of the peptide-7 exporter family (Pep7E).Lactobacillus caseiBL23 encodes two TCS belonging to this group (TCS09 and TCS12) that are located next to two ABC transporters (ABC09 and ABC12), as well as a third Pep7E ABC transporter not genetically associated with any TCS (orphan ABC). This study addressed the involvement of modules TCS09/ABC09 and TCS12/ABC12 in AMP resistance. Results showed that both systems contribute toL. caseiresistance to AMPs, and that each TCS constitutes a functional unit with its corresponding ABC transporter. Analysis of transcriptional levels showed that module 09 is required for the induction of ABC09 expression in response to nisin. In contrast, module 12 controls a wider regulon that encompasses the orphan ABC, thedltoperon (d-alanylation of teichoid acids), and themprFgene (l-lysinylation of phospholipids), thereby controlling properties of the cell envelope. Furthermore, the characterization of adltAmutant showed that Dlt plays a major role in AMP resistance inL. casei. This is the first report on the regulation of the response ofL. caseito AMPs, giving insight into its ability to adapt to the challenging environments that it encounters as a probiotic microorganism.

scholarly journals e-Tendering readiness in construction: the posterior model

2018 ◽  
Vol 18 (2) ◽  
Author(s):  
Moath Al Yahya ◽  
Martin Skitmore ◽  
Adrian Bridge ◽  
Madhav Nepal ◽  
David Cattell
Keyword(s):  
Saudi Arabia ◽  
Conceptual Model ◽  
Structural Equation ◽  
Service Providers ◽  
Empirical Test ◽  
Research Literature ◽  
The Body ◽  
Content Type ◽  
Body Of Knowledge ◽  
First Time

Purpose The purpose of this paper is to varied a conceptual model for e-Tendering readiness in any construction organisation prior of implementing e-Tendering system. Design/methodology/approach Based on conceptual model called e-Tendering readiness model (e-TRM), this paper empirically examines the e-TRM’s interactions and causal relationships between e-Tendering constructs and e-Tendering readiness. The paper uses the structural equation modelling technique to test the hypothesised positive inter-relationships. A questionnaire survey is conducted for respondents of construction organisations in Saudi Arabia to understand their current e-Tendering readiness and importance of e-Tendering variables. Findings Supported by empirical evidence, this paper recognised that three out of nine constructs have direct influences on the e-Tendering readiness. However, one of the constructs, which is for the first time hypothesised and tested has the most effect. Research limitations/implications Ultimately, the empirical test for the e-TRM is conducted in certain case (Saudi Arabia); however, the e-TRM needs to be tested in other case area for more verification. Practical implications The study findings update previous information technology/information system models in construction by adding this tested model to the research literature on traditional and electronic tendering and the body of knowledge in the construction industry. Originality/value The service providers construct is proposed and tested for the first time, which is necessary to support the successful e-Tendering implementation.

scholarly journals Multidrug-ResistantAcinetobacter baumanniiChloramphenicol Resistance Requires an Inner Membrane Permease

2018 ◽  
Vol 62 (8) ◽  
Author(s):  
Andrew P.-A. Karalewitz ◽  
Samuel I. Miller
Keyword(s):  
Cell Envelope ◽  
Multidrug Resistant ◽  
Permeability Barrier ◽  
Gram Negative ◽  
Content Type ◽  
Primary Determinant ◽  
Unique Cell ◽  
Content Support ◽  
Hospital Acquired ◽  
Small Hydrophobic

ABSTRACTAcinetobacter baumanniiis a Gram-negative organism that is a cause of hospital-acquired multidrug-resistant (MDR) infections.A. baumanniihas a unique cell surface compared to those of many other Gram-negative pathogens in that it can live without lipopolysaccharide (LPS) and it has a high content of cardiolipin in the outer membrane. Therefore, to better understand the cell envelope and mechanisms of MDRA. baumannii, we screened a transposon library for mutants with defective permeability barrier function, defined as a deficiency in the ability to exclude the phosphatase chromogenic substrate 5-bromo-4-chloro-3-indolylphosphate (XP). We identified multiple mutants with mutations in the ABUW_0982 gene, predicted to encode a permease broadly present inA. baumanniiisolates with increased susceptibility to the ribosome-targeting antibiotic chloramphenicol (CHL). Moreover, compared to other known CHL resistance genes, such as chloramphenicol acyltransferase genes, we found that ABUW_0982 is the primary determinant of intrinsic CHL resistance inA. baumanniistrain 5075 (Ab5075), an important isolate responsible for severe MDR infections in humans. Finally, studies measuring the efflux of chloramphenicol and expression of ABUW_0982 in CHL-susceptibleEscherichia colisupport the conclusion that ABUW_0982 encodes a single-component efflux protein with specificity for small, hydrophobic molecules, including CHL.

The art of tastings: enhancing the arts festival experience

2018 ◽  
Vol 9 (3) ◽  
pp. 246-265 ◽  
Author(s):  
Armand Viljoen ◽  
Martinette Kruger ◽  
Melville Saayman
Keyword(s):  
The Body ◽  
Sparkling Wine ◽  
Content Type ◽  
Body Of Knowledge ◽  
Arts Festivals ◽  
The Arts ◽  
Art And Culture ◽  
Arts Festival ◽  
First Time ◽  
Practical Implications

PurposeThe role and importance of arts festivals are well documented within the festival and events literature. Art and culture, as well as the subsequent enhancement thereof, are especially significant in multicultural societies. However, little is known regarding the role of culinary experiences within an arts festival setting. The paper aims to discuss these issues.Design/methodology/approachThe case study was a well-known and popular Afrikaans national arts festival held annually in Potchefstroom, South Africa. Visitors to three distinct tasting experiences (brandy, whisky and sparkling wine, including Méthode Cap Classique), offered as part of the festival programme, were surveyed.FindingsIn the analyses, 292 completed questionnaires were included, which revealed three managerial factors for a successful tasting experience, as well as six tasting experience dimensions. In all cases, the experiences exceeded the expectations. This research greatly contributes towards the body of knowledge regarding tasting experiences at national arts festivals, an aspect that has not been researched to date.Practical implicationsBased on the results, practical implications are provided to enhance the current tasting experiences as well as visitor loyalty. This research is a stepping stone towards understanding the needs and preferences of the visitors, as well as identifying how the festival can capitalise on delivering these experiences.Originality/valueThis research identified for the first time the factors that contribute to a memorable tasting experience, as well as evaluated the tasting experience dimensions.

Zeolites Fit For A Crown: Probing Host-Guest Interactions with Thermogravimetric Methods

2018 ◽  
Author(s):  
Asel Sartbaeva ◽  
Paul R. Raithby ◽  
Remi Castaing ◽  
Antony Nearchou
Keyword(s):  
Mass Spectrometry ◽  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Petrochemical Industry ◽  
Rational Use ◽  
New Methodologies ◽  
First Time ◽  
Kinetics Of

Through a combination of thermogravimetry, mass spectrometry and differential thermal analysis, we demonstrate for the first time that all four zeolites show experimental differences in their host-guest interactions with 18C6. In addition, we have estimated the kinetics of 18C6 decomposition, which is a technique that has not been applied to zeolites previously. Using these findings as a toolkit, a more rational use of OSDAs can be utilised to prepare designer zeolites. Furthermore, the new methodologies presented herein can be applied to current zeolites, such as MFI-type zeolites used in the petrochemical industry.

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