scholarly journals TetR-family transcription factors in Gram-negative bacteria: conservation, variation and implications for efflux-mediated antimicrobial resistance

BMC Genomics ◽  
2019 ◽  
Vol 20 (1) ◽  
Author(s):  
A. L. Colclough ◽  
J. Scadden ◽  
J. M. A. Blair
Keyword(s):  
Gene Expression ◽  
Antimicrobial Resistance ◽  
Biofilm Formation ◽  
Pathogenic Bacteria ◽  
Efflux Pump ◽  
Regulate Gene Expression ◽  
Gram Negative ◽  
Single Target ◽  
Dna Binding Factors ◽  
Wide Scale

Abstract Background TetR-family transcriptional regulators (TFTRs) are DNA binding factors that regulate gene expression in bacteria. Well-studied TFTRs, such as AcrR, which regulates efflux pump expression, are usually encoded alongside target operons. Recently, it has emerged that there are many TFTRs which act as global multi-target regulators. Our classical view of TFTRs as simple, single-target regulators therefore needs to be reconsidered. As some TFTRs regulate essential processes (e.g. metabolism) or processes which are important determinants of resistance and virulence (e.g. biofilm formation and efflux gene expression) and as TFTRs are present throughout pathogenic bacteria, they may be good drug discovery targets for tackling antimicrobial resistant infections. However, the prevalence and conservation of individual TFTR genes in Gram-negative species, has to our knowledge, not yet been studied. Results Here, a wide-scale search for TFTRs in available proteomes of clinically relevant pathogens Salmonella and Escherichia species was performed and these regulators further characterised. The majority of identified TFTRs are involved in efflux regulation in both Escherichia and Salmonella. The percentage variance in TFTR genes of these genera was found to be higher in those regulating genes involved in efflux, bleach survival or biofilm formation than those regulating more constrained processes. Some TFTRs were found to be present in all strains and species of these two genera, whereas others (i.e. TetR) are only present in some strains and some (i.e. RamR) are genera-specific. Two further pathogens on the WHO priority pathogen list (K. pneumoniae and P. aeruginosa) were then searched for the presence of the TFTRs conserved in Escherichia and Salmonella. Conclusions Through bioinformatics and literature analyses, we present that TFTRs are a varied and heterogeneous family of proteins required for the regulation of numerous important processes, with consequences to antimicrobial resistance and virulence, and that the roles and responses of these proteins are frequently underestimated.

scholarly journals Genetic Determinants of Salmonella Resistance to the Biofilm-Inhibitory Effects of a Synthetic 4-Oxazolidinone Analog

2020 ◽  
Vol 86 (20) ◽  
Author(s):  
K. F. Griewisch ◽  
J. G. Pierce ◽  
J. R. Elfenbein
Keyword(s):  
Gene Expression ◽  
Natural Products ◽  
Antimicrobial Resistance ◽  
Salmonella Enterica ◽  
Biofilm Formation ◽  
Efflux Pump ◽  
Single Gene ◽  
Synthetic Analogs ◽  
Content Type ◽  
Matrix Gene

ABSTRACT Biofilms formed by Salmonella enterica are a frequent source of food supply contamination. Since biofilms are inherently resistant to disinfection, new agents capable of preventing biofilm formation are needed. Synthetic analogs of 4-oxazolidinone containing natural products have shown promise as antibiofilm compounds against Gram-positive bacteria. The purpose of our study was 2-fold: to establish the antibiofilm effects and mechanism of action of a synthetic 4-oxazolidinone analog (JJM-ox-3-70) and to establish mechanisms of resistance to this compound in Salmonella enterica serovar Typhimurium (S. Typhimurium). JJM-ox-3-70 inhibited biofilm formation but had no effect on cell growth. The antibiofilm effects were linked to disruption of curli fimbriae and flagellar gene expression and alteration in swimming motility, suggesting an effect on multiple cellular processes. Using a 2-step screening approach of defined multigene and single-gene deletion mutant libraries, we identified 3 mutants that produced less biofilm in the presence of JJM-ox-3-70 than the isogenic WT, with phenotypes reversed by complementation in trans. Genes responsible for S. Typhimurium resistance to the compound included acrB, a component of the major drug efflux pump AcrAB-TolC, and two genes of unknown function (STM0437 and STM1292). The results of this study suggest that JJM-ox-3-70 inhibits biofilm formation by indirect inhibition of extracellular matrix production that may be linked to disruption of flagellar motility. Further work is needed to establish the role of the newly characterized genes as potential mechanisms of biofilm intrinsic antimicrobial resistance. IMPORTANCE Biofilms are resistant to killing by disinfectants and antimicrobials. S. enterica biofilms facilitate long-term host colonization and persistence in food processing environments. Synthetic analogs of 4-oxazolidinone natural products show promise as antibiofilm agents. Here, we show that a synthetic 4-oxazolidinone analog inhibits Salmonella biofilm through effects on both motility and biofilm matrix gene expression. Furthermore, we identify three genes that promote Salmonella resistance to the antibiofilm effects of the compound. This work provides insight into the mechanism of antibiofilm effects of a synthetic 4-oxazolidinone analog in Gram-negative bacteria and demonstrates new mechanisms of intrinsic antimicrobial resistance in Salmonella biofilms.

scholarly journals Can't you hear me knocking: contact-dependent competition and cooperation in bacteria

2017 ◽  
Vol 1 (1) ◽  
pp. 75-83 ◽  
Author(s):  
Allison M. Jones ◽  
David A. Low ◽  
Christopher S. Hayes
Keyword(s):  
Gene Expression ◽  
Biofilm Formation ◽  
Gram Negative Bacteria ◽  
Competitive Growth ◽  
Regulate Gene Expression ◽  
Gram Negative ◽  
Competition And Cooperation ◽  
Dependent Growth ◽  
Contact Dependent Growth Inhibition ◽  
Regulate Gene

Microorganisms are in constant competition for growth niches and environmental resources. In Gram-negative bacteria, contact-dependent growth inhibition (CDI) systems link the fate of one cell with its immediate neighbor through touch-dependent, receptor-mediated toxin delivery. Though discovered for their ability to confer a competitive growth advantage, CDI systems also play significant roles in intersibling cooperation, promoting both auto-aggregation and biofilm formation. In this review, we detail the mechanisms of CDI toxin delivery and consider how toxin exchange between isogenic sibling cells could regulate gene expression.

scholarly journals Antimicrobial Susceptibility Pattern of Gram-Negative Bacterial Isolates from Raw Chicken Meat Samples

2019 ◽  
Vol 6 ◽  
pp. 89-95
Author(s):  
Neha Gautam ◽  
Rojan Poudel ◽  
Binod Lekhak ◽  
Milan Kumar Upreti
Keyword(s):  
Antimicrobial Resistance ◽  
Pathogenic Bacteria ◽  
Chicken Meat ◽  
Food Microbiology ◽  
Diffusion Method ◽  
Resistance Pattern ◽  
Kathmandu Valley ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Meat Samples

Objectives: This research aims to study the microbial quality of chicken meat available in retail shop of Kathmandu Valley. Methods:  This Study was conducted from June to December 2018 in three different districts of Kathmandu Valley. Samples were collected in sterile plastic bags, labeled properly and stored in an icebox and transported to the Food Microbiology laboratory of Golden Gate International College.  During sample preparation, 25 grams of each sample was taken and transferred to sterile flasks containing 225 ml of buffered peptone water. Potential pathogenic Gram-negative bacteria were isolated by using respective selective media and identified by biochemical test. Antibiotic susceptibility profile of isolates was carried out by Kirby-Bauer disc diffusion method according to CLSI 2017 guideline. Results: Of total 81 chicken meat samples processed; 201 Gram negative bacteria were isolated.  E. coli (100%) was the dominant Gram-negative isolates, followed by Citrobacter spp (62.96%), Pseudomonas spp (40.74%), Proteus spp (19.75%), Salmonella spp (16.04%) and Klebsiella spp (8.64%) respectively. No any multidrug isolates were detected. Conclusion: The study showed that the raw chicken meat samples of Kathmandu valley was highly contaminated with Gram negative potential pathogenic bacteria. Antimicrobial resistance pattern shown by the isolates may indicates that there is not overuse of drug in animals and the less chance of risk of increasing antimicrobial resistance.

scholarly journals The carbon source influences the efflux pump-mediated antimicrobial resistance in clinically important Gram-negative bacteria

2012 ◽  
Vol 67 (4) ◽  
pp. 921-927 ◽  
Author(s):  
N. A. Villagra ◽  
J. A. Fuentes ◽  
M. R. Jofre ◽  
A. A. Hidalgo ◽  
P. Garcia ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Carbon Source ◽  
Efflux Pump ◽  
Gram Negative Bacteria ◽  
Gram Negative

scholarly journals Two Component Regulatory Systems and Antibiotic Resistance in Gram-Negative Pathogens

2019 ◽  
Vol 20 (7) ◽  
pp. 1781 ◽  
Author(s):  
Anjali Y. Bhagirath ◽  
Yanqi Li ◽  
Rakesh Patidar ◽  
Katherine Yerex ◽  
Xiaoxue Ma ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Antimicrobial Resistance ◽  
Pathogenic Bacteria ◽  
Current Knowledge ◽  
Regulation Of Gene Expression ◽  
Gram Negative ◽  
Environmental Signals ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

Gram-negative pathogens such as Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa are the leading cause of nosocomial infections throughout the world. One commonality shared among these pathogens is their ubiquitous presence, robust host-colonization and most importantly, resistance to antibiotics. A significant number of two-component systems (TCSs) exist in these pathogens, which are involved in regulation of gene expression in response to environmental signals such as antibiotic exposure. While the development of antimicrobial resistance is a complex phenomenon, it has been shown that TCSs are involved in sensing antibiotics and regulating genes associated with antibiotic resistance. In this review, we aim to interpret current knowledge about the signaling mechanisms of TCSs in these three pathogenic bacteria. We further attempt to answer questions about the role of TCSs in antimicrobial resistance. We will also briefly discuss how specific two-component systems present in K. pneumoniae, A. baumannii, and P. aeruginosa may serve as potential therapeutic targets.

scholarly journals Involvement of the AcrAB-TolC Efflux Pump in the Resistance, Fitness, and Virulence of Enterobacter cloacae

2012 ◽  
Vol 56 (4) ◽  
pp. 2084-2090 ◽  
Author(s):  
Astrid Pérez ◽  
Margarita Poza ◽  
Ana Fernández ◽  
Maria del Carmen Fernández ◽  
Susana Mallo ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Pathogenic Bacteria ◽  
Efflux Pump ◽  
Enterobacter Cloacae ◽  
Efflux Pumps ◽  
Clinical Isolates ◽  
Wild Type ◽  
Content Type

ABSTRACTMultidrug efflux pumps have emerged as important mechanisms of antimicrobial resistance in bacterial pathogens. In order to cause infection, pathogenic bacteria require mechanisms to avoid the effects of host-produced compounds, and express efflux pumps may accomplish this task. In this study, we evaluated the effect of the inactivation of AcrAB-TolC on antimicrobial resistance, fitness, and virulence inEnterobacter cloacae, an opportunistic pathogen usually involved in nosocomial infections. Two different clinical isolates ofE. cloacaewere used, EcDC64 (multidrug resistance overexpressing the AcrAB-TolC efflux pump) and Jc194 (basal AcrAB-TolC expression). TheacrAandtolCgenes were deleted in strains EcDC64 and Jc194 to produce, respectively, EcΔacrAand EcΔtolCand JcΔacrAand JcΔtolCknockout (KO) derivatives. Antibiotic susceptibility testing was performed with all isolates, and we discovered that these mechanisms are involved in the resistance ofE. cloacaeto several antibiotics. Competition experiments were also performed with wild-type and isogenic KO strains. The competition index (CI), defined as the mutant/wild-type ratio, revealed that theacrAandtolCgenes both affect the fitness ofE. cloacae, as fitness was clearly reduced in theacrAandtolCKO strains. The median CI values obtainedin vitroandin vivowere, respectively, 0.42 and 0.3 for EcDC64/EcΔacrA, 0.24 and 0.38 for EcDC64/EcΔtolC, 0.15 and 0.11 for Jc194/JcΔacrA, and 0.38 and 0.39 for Jc194/JcΔtolC. Use of an intraperitoneal mouse model of systemic infection revealed reduced virulence in bothE. cloacaeclinical strains when either theacrAortolCgene was inactivated. In conclusion, the structural components of the AcrAB-TolC efflux pump appear to play a role in antibiotic resistance as well as environmental adaptation and host virulence in clinical isolates ofE. cloacae.

scholarly journals roles Hrp-dependent effector proteins and hrp gene regulation as determinants of virulence and host-specificity in Erwinia stewartii and E. herbicola pvs. gypsophilae and betae

2005 ◽  
Author(s):  
David L. Coplin ◽  
Shulamit Manulis ◽  
Isaac Barash
Keyword(s):  
Gene Expression ◽  
Host Specificity ◽  
Pathogenic Bacteria ◽  
Effector Proteins ◽  
Host Cells ◽  
Secretion Systems ◽  
Gram Negative ◽  
Regulatory Cascade ◽  
Effector Genes ◽  
Erwinia Stewartii

Gram-negative plant pathogenic bacteria employ specialized type-III secretion systems (TTSS) to deliver an arsenal of pathogenicity proteins directly into host cells. These secretion systems are encoded by hrp genes (for hypersensitive response and pathogenicity) and the effector proteins by so-called dsp or avr genes. The functions of effectors are to enable bacterial multiplication by damaging host cells and/or by blocking host defenses. We characterized essential hrp gene clusters in the Stewart's Wilt of maize pathogen, Pantoea stewartii subsp. stewartii (Pnss; formerly Erwinia stewartii) and the gall-forming bacterium, Pantoea agglomerans (formerly Erwinia herbicola) pvs. gypsophilae (Pag) and betae (Pab). We proposed that the virulence and host specificity of these pathogens is a function of a) the perception of specific host signals resulting in bacterial hrp gene expression and b) the action of specialized signal proteins (i.e. Hrp effectors) delivered into the plant cell. The specific objectives of the proposal were: 1) How is the expression of the hrp and effector genes regulated in response to host cell contact and the apoplastic environment? 2) What additional effector proteins are involved in pathogenicity? 3) Do the presently known Pantoea effector proteins enter host cells? 4) What host proteins interact with these effectors? We characterized the components of the hrp regulatory cascade (HrpXY ->7 HrpS ->7 HrpL ->7 hrp promoters), showed that they are conserved in both Pnss and Fag, and discovered that the regulation of the hrpS promoter (hrpSp) may be a key point in integrating apoplastic signals. We also analyzed the promoters recognized by HrpL and demonstrated the relationship between their composition and efficiency. Moreover, we showed that promoter strength can influence disease expression. In Pnss, we found that the HrpXY two-component signal system may sense the metabolic status of the bacterium and is required for full hrp gene expression in planta. In both species, acyl-homoserine lactone-mediated quorum sensing may also regulate epiphytic fitness and/or pathogenicity. A common Hrp effector protein, DspE/WtsE, is conserved and required for virulence of both species. When introduced into corn cells, Pnss WtsE protein caused water-soaked lesions. In other plants, it either caused cell death or acted as an Avr determinant. Using a yeast- two-hybrid system, WtsE was shown to interact with a number of maize signal transduction proteins that are likely to have roles in either programmed cell death or disease resistance. In Pag and Pab, we have characterized the effector proteins HsvG, HsvB and PthG. HsvG and HsvB are homologous proteins that determine host specificity of Pag and Pab on gypsophila and beet, respectively. Both possess a transcriptional activation domain that functions in yeast. PthG was found to act as an Avr determinant on multiple beet species, but was required for virulence on gypsophila. In addition, we demonstrated that PthG acts within the host cell. Additional effector genes have been characterized on the pathogenicity plasmid, pPATHₚₐg, in Pag. A screen for HrpL- regulated genes in Pnsspointed up 18 candidate effector proteins and four of these were required for full virulence. It is now well established that the virulence of Gram-negative plant pathogenic bacteria is governed by Hrp-dependent effector proteins. However; the mode of action of many effectors is still unresolved. This BARD supported research will significantly contribute to the understanding of how Hrp effectors operate in Pantoea spp. and how they control host specificity and affect symptom production. This may lead to novel approaches for genetically engineering plants resistant to a wide range of bacterial pathogens by inactivating the Hrp effectors with "plantabodies" or modifying their receptors, thereby blocking the induction of the susceptible response. Alternatively, innovative technologies could be used to interfere with the Hrp regulatory cascade by blocking a critical step or mimicking plant or quorum sensing signals.   

scholarly journals ToxR mediates the antivirulence activity of phenyl-arginine-β-naphthylamide to attenuate Vibrio cholerae virulence.

2021 ◽  
Author(s):  
Yuding Weng ◽  
Thomas F. Bina ◽  
X. Renee Bina ◽  
James E. Bina
Keyword(s):  
Antimicrobial Resistance ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Efflux Pump ◽  
Feedback Mechanism ◽  
Gram Negative ◽  
Factor Production ◽  
Regulatory Circuit ◽  
Efflux Pump Inhibitors ◽  
Virulence Factor Production

Multidrug efflux systems belonging to the resistance-nodulation-cell division (RND) family are ubiquitous in Gram negative bacteria and critical for antimicrobial resistance. This realization has led to efforts to develop efflux pump inhibitors (EPI) for use as adjuvants for antibiotic treatment of resistant organisms. However, the functions of RND transporters extend beyond antimicrobial resistance to include physiological functions that are critical for pathogenesis, suggesting that EPIs could also be used as antivirulence therapeutics. This was documented in the enteric pathogen Vibrio cholerae where EPIs were shown to attenuate the production of the critical virulence factors cholera toxin (CT) and the toxin coregulated pilus (TCP). In this study we investigated the antivirulence mechanism of action of the EPI phenyl-arginine-β-naphthylamide (PAβN) on V. cholerae. Using bioassays, we documented that PAβN inhibited virulence factor production in three epidemic V. cholerae isolates. Transcriptional reporter studies and mutant analysis indicated that PAβN initiated a ToxR-dependent regulatory circuit to activate leuO expression and that LeuO repressed the expression of the critical virulence activator aphA to attenuate CT and TCP production. The antivirulence activity of PAβN was found to be dependent on the ToxR periplasmic sensing domain suggesting that a feedback mechanism was involved in its activity. Collectively the data indicated that PAβN inhibited V. cholerae virulence factor production by activating a ToxR-dependent metabolic feedback mechanism to repress the expression of the ToxR virulence regulon. This suggests that efflux pump inhibitors could be used as antivirulence therapeutics for the treatment of cholera and perhaps other gram negative pathogens.

scholarly journals Dynamic Boolean modelling reveals the influence of energy supply on bacterial efflux pump expression

2021 ◽  
Author(s):  
Ryan Kerr ◽  
Sara Jabbari ◽  
Jessica M A Blair ◽  
Iain Johnston
Keyword(s):  
Gene Expression ◽  
Antimicrobial Resistance ◽  
Energy Supply ◽  
Regulatory Networks ◽  
Efflux Pump ◽  
Bacterial Species ◽  
Efflux Pumps ◽  
Resistant Bacteria ◽  
Energy Availability ◽  
Bacterial Populations

Antimicrobial resistance (AMR) is a global health issue. One key factor contributing to AMR is the ability of bacteria to export drugs through efflux pumps, which relies on the ATP-dependent expression and interaction of several controlling genes. Recent studies have shown significant cell-to-cell ATP variability exists within clonal bacterial populations, but the contribution of intrinsic cell-to-cell ATP heterogeneity is generally overlooked in understanding efflux pumps. Here, we consider how ATP variability influences gene regulatory networks controlling expression of efflux pump genes in two bacterial species. We develop and apply a generalisable Boolean modelling framework, developed to incorporate the dependence of gene expression dynamics on available cellular energy supply. Theoretical results show differences in energy availability can cause pronounced downstream heterogeneity in efflux gene expression. Cells with higher energy availability have a superior response to stressors. Further, in the absence of stress, model bacteria develop heterogeneous pulses of efflux pump gene expression which contribute to a sustained sub-population of cells with increased efflux expression activity, potentially conferring a continuous pool of intrinsically resistant bacteria. This modelling approach thus reveals an important source of heterogeneity in cell responses to antimicrobials and sheds light on potentially targetable aspects of efflux pump-related antimicrobial resistance.

scholarly journals PATHOGENIC BACTERIA IN WATERS AND DRINKING WATER-ASSOCIATED BIOFILMS

2017 ◽  
pp. 50-61
Author(s):  
Zvezdimira Tsvetanova ◽  
Hristo Najdenski
Keyword(s):  
Drinking Water ◽  
Antimicrobial Resistance ◽  
Biofilm Formation ◽  
Pathogenic Bacteria ◽  
Natural Waters ◽  
Interspecies Interactions ◽  
Formation Potential ◽  
Current State ◽  
Biofilm Community

In this review, the dissemination of bacterial pathogens in natural waters and the mechanisms of their transmission in drinking water, and the role of water-associated biofilms for their survival or growth are discussed. The current state of the studies on biofilm-formation potential of the emerged pathogens in drinking water and the role of interspecies interactions for attachment and survival of pathogenic bacteria in the biofilm community is summarized. The contribution of the biofilms for increasing antimicrobial resistance of pathogens is discussed.

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