1
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Shapiro JA. A very brief note on why bacterial evolution has physiology. J Physiol 2024; 602:2395-2399. [PMID: 37641409 DOI: 10.1113/jp284409] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 08/16/2023] [Indexed: 08/31/2023] Open
Abstract
The majority of bacteria live and evolve in surface biofilms. Both growth in biofilms and horizontal transfer of DNA are regulated by quorum-sensing pheromone signals. The common regulation of bacterial surface growth and DNA transfers illustrates how physiology contributes to bacterial evolution.
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Affiliation(s)
- James A Shapiro
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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2
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Liu F, Luo Y, Xu T, Lin H, Qiu Y, Li B. Current examining methods and mathematical models of horizontal transfer of antibiotic resistance genes in the environment. Front Microbiol 2024; 15:1371388. [PMID: 38638913 PMCID: PMC11025395 DOI: 10.3389/fmicb.2024.1371388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 03/11/2024] [Indexed: 04/20/2024] Open
Abstract
The increasing prevalence of antibiotic resistance genes (ARGs) in the environment has garnered significant attention due to their health risk to human beings. Horizontal gene transfer (HGT) is considered as an important way for ARG dissemination. There are four general routes of HGT, including conjugation, transformation, transduction and vesiduction. Selection of appropriate examining methods is crucial for comprehensively understanding characteristics and mechanisms of different HGT ways. Moreover, combined with the results obtained from different experimental methods, mathematical models could be established and serve as a powerful tool for predicting ARG transfer dynamics and frequencies. However, current reviews of HGT for ARG spread mainly focus on its influencing factors and mechanisms, overlooking the important roles of examining methods and models. This review, therefore, delineated four pathways of HGT, summarized the strengths and limitations of current examining methods, and provided a comprehensive summing-up of mathematical models pertaining to three main HGT ways of conjugation, transformation and transduction. Finally, deficiencies in current studies were discussed, and proposed the future perspectives to better understand and assess the risks of ARG dissemination through HGT.
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Affiliation(s)
- Fan Liu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, China
| | - Yuqiu Luo
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, China
| | - Tiansi Xu
- School of Environment, Tsinghua University, Beijing, China
| | - Hai Lin
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, China
| | - Yong Qiu
- School of Environment, Tsinghua University, Beijing, China
| | - Bing Li
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, China
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3
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Michaelis C, Grohmann E. Horizontal Gene Transfer of Antibiotic Resistance Genes in Biofilms. Antibiotics (Basel) 2023; 12:antibiotics12020328. [PMID: 36830238 PMCID: PMC9952180 DOI: 10.3390/antibiotics12020328] [Citation(s) in RCA: 49] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 02/08/2023] Open
Abstract
Most bacteria attach to biotic or abiotic surfaces and are embedded in a complex matrix which is known as biofilm. Biofilm formation is especially worrisome in clinical settings as it hinders the treatment of infections with antibiotics due to the facilitated acquisition of antibiotic resistance genes (ARGs). Environmental settings are now considered as pivotal for driving biofilm formation, biofilm-mediated antibiotic resistance development and dissemination. Several studies have demonstrated that environmental biofilms can be hotspots for the dissemination of ARGs. These genes can be encoded on mobile genetic elements (MGEs) such as conjugative and mobilizable plasmids or integrative and conjugative elements (ICEs). ARGs can be rapidly transferred through horizontal gene transfer (HGT) which has been shown to occur more frequently in biofilms than in planktonic cultures. Biofilm models are promising tools to mimic natural biofilms to study the dissemination of ARGs via HGT. This review summarizes the state-of-the-art of biofilm studies and the techniques that visualize the three main HGT mechanisms in biofilms: transformation, transduction, and conjugation.
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Biofilm through the Looking Glass: A Microbial Food Safety Perspective. Pathogens 2022; 11:pathogens11030346. [PMID: 35335670 PMCID: PMC8954374 DOI: 10.3390/pathogens11030346] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/08/2022] [Accepted: 03/10/2022] [Indexed: 02/06/2023] Open
Abstract
Food-processing facilities harbor a wide diversity of microorganisms that persist and interact in multispecies biofilms, which could provide an ecological niche for pathogens to better colonize and gain tolerance against sanitization. Biofilm formation by foodborne pathogens is a serious threat to food safety and public health. Biofilms are formed in an environment through synergistic interactions within the microbial community through mutual adaptive response to their long-term coexistence. Mixed-species biofilms are more tolerant to sanitizers than single-species biofilms or their planktonic equivalents. Hence, there is a need to explore how multispecies biofilms help in protecting the foodborne pathogen from common sanitizers and disseminate biofilm cells from hotspots and contaminate food products. This knowledge will help in designing microbial interventions to mitigate foodborne pathogens in the processing environment. As the global need for safe, high-quality, and nutritious food increases, it is vital to study foodborne pathogen behavior and engineer new interventions that safeguard food from contamination with pathogens. This review focuses on the potential food safety issues associated with biofilms in the food-processing environment.
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5
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Conwell M, Dooley J, Naughton PJ. Enterococcal biofilm - a nidus for antibiotic resistance transfer? J Appl Microbiol 2022; 132:3444-3460. [PMID: 34990042 PMCID: PMC9306868 DOI: 10.1111/jam.15441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 08/03/2021] [Accepted: 01/03/2022] [Indexed: 11/30/2022]
Abstract
Enterococci, important agents of hospital acquired infection, are listed on the WHO list of multi-drug resistant pathogens commonly encountered in hospital acquired infections are now of increasing importance, due to the development of strains resistant to multiple antibiotics. Enterococci are also important microorganisms in the environment and their presence is frequently used as an indicator of faecal pollution. Their success is related to their ability to survive within a broad range of habitats and the ease by which they acquire mobile genetic elements, including plasmids, from other bacteria. The enterococci are frequently present within a bacterial biofilm which provides stability and protection to the bacterial population along with an opportunity for a variety of bacterial interactions. Enterococci can accept extrachromosomal DNA both from within its own species and from other bacterial species and this is enhanced by the proximity of the donor and recipient strains. It is this exchange of genetic material that makes the role of biofilm such an important aspect of the success of enterococci. There remain many questions regarding the most suitable model systems to study enterococci in biofilm and regarding the transfer of genetic material including antibiotic resistance in these biofilms. This review focuses on some important aspects of biofilm in the context of horizontal gene transfer (HGT) in enterococci.
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Affiliation(s)
- M Conwell
- The Nutrition Innovation Centre for Food and Health (NICHE), School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Co. Londonderry, BT52 1SA
| | - Jsg Dooley
- The Nutrition Innovation Centre for Food and Health (NICHE), School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Co. Londonderry, BT52 1SA
| | - P J Naughton
- The Nutrition Innovation Centre for Food and Health (NICHE), School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, Co. Londonderry, BT52 1SA
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6
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Barnes AMT, Frank KL, Dale JL, Manias DA, Powers JL, Dunny GM. Enterococcus faecalis colonizes and forms persistent biofilm microcolonies on undamaged endothelial surfaces in a rabbit endovascular infection model. FEMS MICROBES 2021; 2:xtab014. [PMID: 34734186 PMCID: PMC8557322 DOI: 10.1093/femsmc/xtab014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 09/23/2021] [Indexed: 01/03/2023] Open
Abstract
Infectious endocarditis (IE) is an uncommon disease with significant morbidity and mortality. The pathogenesis of IE has historically been described as a cascade of host-specific events beginning with endothelial damage and thrombus formation and followed by bacterial colonization of the nascent thrombus. Enterococcus faecalis is a Gram-positive commensal bacterial member of the gastrointestinal tract microbiota in most terrestrial animals and a leading cause of opportunistic biofilm-associated infections, including endocarditis. Here, we provide evidence that E. faecalis can colonize the endocardial surface without pre-existing damage and in the absence of thrombus formation in a rabbit endovascular infection model. Using previously described light and scanning electron microscopy techniques, we show that inoculation of a well-characterized E. faecalis lab strain in the marginal ear vein of New Zealand White rabbits resulted in rapid colonization of the endocardium throughout the heart within 4 days of administration. Unexpectedly, ultrastructural imaging revealed that the microcolonies were firmly attached directly to the endocardium in areas without morphological evidence of gross tissue damage. Further, the attached bacterial aggregates were not associated with significant cellular components of coagulation or host extracellular matrix damage repair (i.e. platelets). These results suggest that the canonical model of mechanical surface damage as a prerequisite for bacterial attachment to host sub-endothelial components is not required. Furthermore, these findings are consistent with a model of initial establishment of stable, endocarditis-associated E. faecalis biofilm microcolonies that may provide a reservoir for the eventual valvular infection characteristic of clinical endocarditis. The similarities between the E. faecalis colonization and biofilm morphologies seen in this rabbit endovascular infection model and our previously published murine gastrointestinal colonization model indicate that biofilm production and common host cell attachment factors are conserved in disparate mammalian hosts under both commensal and pathogenic contexts.
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Affiliation(s)
- Aaron M T Barnes
- Department of Microbiology and Immunology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA
| | - Kristi L Frank
- Department of Microbiology and Immunology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA
| | - Jennifer L Dale
- Department of Microbiology and Immunology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA
| | - Dawn A Manias
- Department of Microbiology and Immunology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA
| | - Jennifer L Powers
- Department of Microbiology and Immunology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA
| | - Gary M Dunny
- Department of Microbiology and Immunology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA
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7
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Comparative Biofilm Assays Using Enterococcus faecalis OG1RF Identify New Determinants of Biofilm Formation. mBio 2021; 12:e0101121. [PMID: 34126766 PMCID: PMC8262879 DOI: 10.1128/mbio.01011-21] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Enterococcus faecalis is a common commensal organism and a prolific nosocomial pathogen that causes biofilm-associated infections. Numerous E. faecalis OG1RF genes required for biofilm formation have been identified, but few studies have compared genetic determinants of biofilm formation and biofilm morphology across multiple conditions. Here, we cultured transposon (Tn) libraries in CDC biofilm reactors in two different media and used Tn sequencing (TnSeq) to identify core and accessory biofilm determinants, including many genes that are poorly characterized or annotated as hypothetical. Multiple secondary assays (96-well plates, submerged Aclar discs, and MultiRep biofilm reactors) were used to validate phenotypes of new biofilm determinants. We quantified biofilm cells and used fluorescence microscopy to visualize biofilms formed by six Tn mutants identified using TnSeq and found that disrupting these genes (OG1RF_10350, prsA, tig, OG1RF_10576, OG1RF_11288, and OG1RF_11456) leads to significant time- and medium-dependent changes in biofilm architecture. Structural predictions revealed potential roles in cell wall homeostasis for OG1RF_10350 and OG1RF_11288 and signaling for OG1RF_11456. Additionally, we identified growth medium-specific hallmarks of OG1RF biofilm morphology. This study demonstrates how E. faecalis biofilm architecture is modulated by growth medium and experimental conditions and identifies multiple new genetic determinants of biofilm formation.
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A Novel Biofilm Model System to Visualise Conjugal Transfer of Vancomycin Resistance by Environmental Enterococci. Microorganisms 2021; 9:microorganisms9040789. [PMID: 33918930 PMCID: PMC8070047 DOI: 10.3390/microorganisms9040789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 03/30/2021] [Accepted: 04/05/2021] [Indexed: 11/17/2022] Open
Abstract
Enterococci and biofilm-associated infections are a growing problem worldwide, given the rise in antibiotic resistance in environmental and clinical settings. The increasing incidence of antibiotic resistance and its propagation potential within enterococcal biofilm is a concern. This requires a deeper understanding of how enterococcal biofilm develops, and how antibiotic resistance transfer takes place in these biofilms. Enterococcal biofilm assays, incorporating the study of antibiotic resistance transfer, require a system which can accommodate non-destructive, real-time experimentation. We adapted a Gene Frame® combined with fluorescence microscopy as a novel non-destructive platform to study the conjugal transfer of vancomycin resistance in an established enterococcal biofilm.A multi-purpose fluorescent in situ hybridisation (FISH) probe, in a novel application, allowed the identification of low copy number mobile elements in the biofilm. Furthermore, a Hoechst stain and ENU 1470 FISH probe identified Enterococcus faecium transconjugants by excluding Enterococcus faecalis MF06036 donors. Biofilm created with a rifampicin resistant E. faecalis (MW01105Rif) recipient had a transfer efficiency of 2.01 × 10-3; double that of the biofilm primarily created by the donor (E. faecalis MF06036). Conjugation in the mixed enterococcal biofilm was triple the efficiency of donor biofilm. Double antibiotic treatment plus lysozyme combined with live/dead imaging provided fluorescent micrographs identifying de novo enterococcal vancomycin resistant transconjugants inside the biofilm. This is a model system for the further study of antibiotic resistance transfer events in enterococci. Biofilms promote the survival of enterococci and reduce the effectiveness of drug treatment in clinical settings, hence giving enterococci an advantage. Enterococci growing in biofilms exchange traits by means of horizontal gene transfer, but currently available models make study difficult. This work goes some way to providing a non-destructive, molecular imaging-based model system for the detection of antibiotic resistance gene transfer in enterococci.
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Tsegaye MM, Chouhan G, Fentie M, Tyagi P, Nand P. Therapeutic Potential of Green Synthesized Metallic Nanoparticles against Staphylococcus aureus. Curr Drug Res Rev 2021; 13:172-183. [PMID: 33634763 DOI: 10.2174/2589977513666210226123920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 09/08/2020] [Accepted: 11/06/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND The recent treatment challenges posed by the widespread emergence of pathogenic Multidrug-Resistant (MDR) bacterial strains are a cause of huge health troubles worldwide. Infections caused by MDR organisms are associated with longer period of hospitalization, increased mortality, and inflated healthcare costs. Staphylococcus aureus is one of these MDR organisms identified as an urgent threat to human health by the World Health Organization. Infections caused by S. aureus may range from simple cutaneous infestations to life threatening bacteremia. S. aureus infections get easily escalated in severely ill, hospitalized and or immunocompromised patients with incapacitated immune system. Also, in HIV-positive patients S. aureus ranks amongst one of the most common comorbidities where it can further worsen a patient's health condition. At present anti-staphylococcal therapy is reliant typically on chemotherapeutics that are gathering resistance and pose unfavorable side-effects. Thus, newer drugs are required that can bridge these shortcomings and aid effective control against S. aureus. OBJECTIVE In this review, we summarize drug resistance exhibited by S. aureus and lacunae in current anti-staphylococcal therapy, nanoparticles as an alternative therapeutic modality. The focus lays on various green synthesized nanoparticles, their mode of action and application as potent antibacterial compounds against S. aureus. CONCLUSION Use of nanoparticles as anti-bacterial drugs has gained momentum in recent past and green synthesized nanoparticles, which involves microorganisms and plants or their byproducts for synthesis of nanoparticles offer a potent, as well as environment friendly solution in warfare against MDR bacte.
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Affiliation(s)
- Meron Moges Tsegaye
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Knowledge Park III, Greater Noida, Uttar Pradesh. India
| | - Garima Chouhan
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Knowledge Park III, Greater Noida, Uttar Pradesh. India
| | - Molla Fentie
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Knowledge Park III, Greater Noida, Uttar Pradesh. India
| | - Priya Tyagi
- Department of Biotechnology, School of Engineering and Technology, Sharda University, Knowledge Park III, Greater Noida, Uttar Pradesh. India
| | - Parma Nand
- School of Engineering and Technology, Sharda University, Knowledge Park III, Greater Noida, Uttar Pradesh. India
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10
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Zwanzig M. The ecology of plasmid-coded antibiotic resistance: a basic framework for experimental research and modeling. Comput Struct Biotechnol J 2020; 19:586-599. [PMID: 33510864 PMCID: PMC7807137 DOI: 10.1016/j.csbj.2020.12.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 12/16/2020] [Accepted: 12/20/2020] [Indexed: 12/27/2022] Open
Abstract
Many antibiotic resistance genes are associated with plasmids. The ecological success of these mobile genetic elements within microbial communities depends on varying mechanisms to secure their own propagation, not only on environmental selection. Among the most important are the cost of plasmids and their ability to be transferred to new hosts through mechanisms such as conjugation. These are regulated by dynamic control systems of the conjugation machinery and genetic adaptations that plasmid-host pairs can acquire in coevolution. However, in complex communities, these processes and mechanisms are subject to a variety of interactions with other bacterial species and other plasmid types. This article summarizes basic plasmid properties and ecological principles particularly important for understanding the persistence of plasmid-coded antibiotic resistance in aquatic environments. Through selected examples, it further introduces to the features of different types of simulation models such as systems of ordinary differential equations and individual-based models, which are considered to be important tools to understand these complex systems. This ecological perspective aims to improve the way we study and understand the dynamics, diversity and persistence of plasmids and associated antibiotic resistance genes.
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Affiliation(s)
- Martin Zwanzig
- Faculty of Environmental Sciences, Technische Universität Dresden, Pienner Str. 8, D-01737 Tharandt, Germany
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11
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Banderas A, Carcano A, Sia E, Li S, Lindner AB. Ratiometric quorum sensing governs the trade-off between bacterial vertical and horizontal antibiotic resistance propagation. PLoS Biol 2020; 18:e3000814. [PMID: 32797039 PMCID: PMC7449403 DOI: 10.1371/journal.pbio.3000814] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 08/26/2020] [Accepted: 07/20/2020] [Indexed: 11/19/2022] Open
Abstract
Plasmid-mediated horizontal gene transfer of antibiotic resistance and virulence in pathogenic bacteria underlies a major public health issue. Understanding how, in the absence of antibiotic-mediated selection, plasmid-bearing cells avoid being outnumbered by plasmid-free cells is key to developing counterstrategies. Here, we quantified the induction of the plasmidial sex pheromone pathway of Enterococcus faecalis to show that the integration of the stimulatory (mate-sensing) and inhibitory (self-sensing) signaling modules from the pCF10 conjugative plasmid provides a precise measure of the recipient-to-donor ratio, agnostic to variations in population size. Such ratiometric control of conjugation favors vertical plasmid transfer under low mating likelihood and allows activation of conjugation functions only under high mating likelihood. We further show that this strategy constitutes a cost-effective investment into mating effort because overstimulation produces unproductive self-aggregation and growth rate reduction. A mathematical model suggests that ratiometric control of conjugation increases plasmid fitness and predicts a robust long-term, stable coexistence of donors and recipients. Our results demonstrate how population-level parameters can control transfer of antibiotic resistance in bacteria, opening the door for biotic control strategies. The pathogenic bacterium Enterococcus faecalis controls the horizontal gene transfer of antibiotic resistance according to the ratio of non-resistant to resistant bacteria, while remaining agnostic to variation in the total culture density. This ratiometric twist on the well-known phenomenon of quorum-sensing allows investment in expensive conjugative transfer of plasmids only when chances are high, akin to sexual systems in more complex organisms.
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Affiliation(s)
- Alvaro Banderas
- INSERM U1284, Systems engineering and evolution dynamics, Paris, France
- Center for Research and Interdisciplinarity, Université de Paris, Paris, France
- * E-mail: (AB); (ABL)
| | - Arthur Carcano
- INRIA Saclay–Ile-de-France, Palaiseau, France
- USR 3756 IP CNRS, Institut Pasteur, Paris, France
| | - Elisa Sia
- INSERM U1284, Systems engineering and evolution dynamics, Paris, France
- Center for Research and Interdisciplinarity, Université de Paris, Paris, France
| | - Shuang Li
- INSERM U1284, Systems engineering and evolution dynamics, Paris, France
- Center for Research and Interdisciplinarity, Université de Paris, Paris, France
| | - Ariel B. Lindner
- INSERM U1284, Systems engineering and evolution dynamics, Paris, France
- Center for Research and Interdisciplinarity, Université de Paris, Paris, France
- * E-mail: (AB); (ABL)
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12
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Single-Cell Analysis Reveals that the Enterococcal Sex Pheromone Response Results in Expression of Full-Length Conjugation Operon Transcripts in All Induced Cells. J Bacteriol 2020; 202:JB.00685-19. [PMID: 32041799 DOI: 10.1128/jb.00685-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 02/03/2020] [Indexed: 02/07/2023] Open
Abstract
For high-frequency transfer of pCF10 between E. faecalis cells, induced expression of the pCF10 genes encoding conjugative machinery from the prgQ operon is required. This process is initiated by the cCF10 (C) inducer peptide produced by potential recipient cells. The expression timing of prgB, an "early" gene just downstream of the inducible promoter, has been studied extensively in single cells. However, several previous studies suggest that only 1 to 10% of donors induced for early prgQ gene expression actually transfer plasmids to recipients, even at a very high recipient population density. One possible explanation for this is that only a minority of pheromone-induced donors actually transcribe the entire prgQ operon. Such cells would not be able to functionally conjugate but might play another role in the group behavior of donors. Here, we sought to (i) simultaneously assess the presence of RNAs produced from the proximal (early induced transcripts [early Q]) and distal (late Q) portions of the prgQ operon in individual cells, (ii) investigate the prevalence of heterogeneity in induced transcript length, and (iii) evaluate the temporality of induced transcript expression. Using fluorescent in situ hybridization chain reaction (HCR) transcript labeling and single-cell microscopic analysis, we observed that most cells expressing early transcripts (QL, prgB, and prgA) also expressed late transcripts (prgJ, pcfC, and pcfG). These data support the conclusion that, after induction is initiated, transcription likely extends through the end of the conjugation machinery operon for most, if not all, induced cells.IMPORTANCE In Enterococcus faecalis, conjugative plasmids like pCF10 often carry antibiotic resistance genes. With antibiotic treatment, bacteria benefit from plasmid carriage; however, without antibiotic treatment, plasmid gene expression may have a fitness cost. Transfer of pCF10 is mediated by cell-to-cell signaling, which activates the expression of conjugation genes and leads to efficient plasmid transfer. Yet, not all donor cells in induced populations transfer the plasmid. We examined whether induced cells might not be able to functionally conjugate due to premature induced transcript termination. Single-cell analysis showed that most induced cells do, in fact, express all of the genes required for conjugation, suggesting that premature transcription termination within the prgQ operon does not account for failure of induced donor cell gene transfer.
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13
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Novais C, Freitas AR, León-Sampedro R, Peixe L, Coque TM. Methods to Quantify DNA Transfer in Enterococcus. Methods Mol Biol 2020; 2075:111-122. [PMID: 31584158 DOI: 10.1007/978-1-4939-9877-7_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
DNA uptake in Enterococcus normally occurs by conjugation, a natural process that is replicated in biomedical research to assess the transferability of different mobile genetic elements and chromosomal regions as well as to study the host range of plasmids and other conjugative elements. More efficient artificial methods to transform cells with foreign DNA as chemotransformation and electroporation are widely used in molecular genetics. Here, we described conjugation protocols to quantify DNA transfer among Enterococcus and revise current perspectives and lab strains. Protocols of electrotransformation have been previously described in this series.
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Affiliation(s)
- Carla Novais
- Laboratory of Microbiology, Biological Sciences Department, Faculty of Pharmacy, UCIBIO/REQUIMTE, University of Porto, Porto, Portugal.
| | - Ana R Freitas
- Laboratory of Microbiology, Biological Sciences Department, Faculty of Pharmacy, UCIBIO/REQUIMTE, University of Porto, Porto, Portugal
| | - Ricardo León-Sampedro
- Department of Microbiology, Ramón y Cajal Health Research Institute (IRYCIS), Unidad de Resistencia a Antibióticos y Virulencia Bacteriana (RYC-CSIC), CIBER en Epidemiología y Salud Pública (CIBER-ESP), Ramón y Cajal University Hospital, Madrid, Spain
| | - Luísa Peixe
- Laboratory of Microbiology, Biological Sciences Department, Faculty of Pharmacy, UCIBIO/REQUIMTE, University of Porto, Porto, Portugal
| | - Teresa M Coque
- Department of Microbiology, Ramón y Cajal Research Institute (IRYCIS), Madrid, Spain.
- CIBER in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
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14
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Ch’ng JH, Chong KKL, Lam LN, Wong JJ, Kline KA. Biofilm-associated infection by enterococci. Nat Rev Microbiol 2018; 17:82-94. [DOI: 10.1038/s41579-018-0107-z] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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15
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Fernández L, González S, Quiles-Puchalt N, Gutiérrez D, Penadés JR, García P, Rodríguez A. Lysogenization of Staphylococcus aureus RN450 by phages ϕ11 and ϕ80α leads to the activation of the SigB regulon. Sci Rep 2018; 8:12662. [PMID: 30139986 PMCID: PMC6107660 DOI: 10.1038/s41598-018-31107-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 08/10/2018] [Indexed: 12/18/2022] Open
Abstract
Staphylococcus aureus is a major opportunistic pathogen that commonly forms biofilms on various biotic and abiotic surfaces. Also, most isolates are known to carry prophages in their genomes. With this in mind, it seems that acquiring a better knowledge of the impact of prophages on the physiology of S. aureus biofilm cells would be useful for developing strategies to eliminate this pathogen. Here, we performed RNA-seq analysis of biofilm cells formed by S. aureus RN450 and two derived strains carrying prophages ϕ11 and ϕ80α. The lysogenic strains displayed increased biofilm formation and production of the carotenoid pigment staphyloxanthin. These phenotypes could be partly explained by the differences in gene expression displayed by prophage-harboring strains, namely an activation of the alternative sigma factor (SigB) regulon and downregulation of genes controlled by the Agr quorum-sensing system, especially the decreased transcription of genes encoding dispersion factors like proteases. Nonetheless, spontaneous lysis of part of the population could also contribute to the increased attached biomass. Interestingly, it appears that the phage CI protein plays a role in orchestrating these phage-host interactions, although more research is needed to confirm this possibility. Likewise, future studies should examine the impact of these two prophages during the infection.
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Affiliation(s)
- Lucía Fernández
- Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n 33300 -, Villaviciosa, Asturias, Spain.
| | - Silvia González
- Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n 33300 -, Villaviciosa, Asturias, Spain
| | - Nuria Quiles-Puchalt
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8TA, Glasgow, UK
| | - Diana Gutiérrez
- Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n 33300 -, Villaviciosa, Asturias, Spain
| | - José R Penadés
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8TA, Glasgow, UK
| | - Pilar García
- Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n 33300 -, Villaviciosa, Asturias, Spain
| | - Ana Rodríguez
- Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n 33300 -, Villaviciosa, Asturias, Spain
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16
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Mechanistic Features of the Enterococcal pCF10 Sex Pheromone Response and the Biology of Enterococcus faecalis in Its Natural Habitat. J Bacteriol 2018; 200:JB.00733-17. [PMID: 29437851 DOI: 10.1128/jb.00733-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Conjugative transfer of plasmids in enterococci is promoted by intercellular communication using peptide pheromones. The regulatory mechanisms that control transfer have been extensively studied in vitro However, the complicated systems that regulate the spread of these plasmids did not evolve in the laboratory test tube, and remarkably little is known about this form of signaling in the intestinal tract, the primary niche of these organisms. Because the evolution of Enterococcus faecalis strains and their coresident pheromone-inducible plasmids, such as pCF10, have occurred in the gastrointestinal (GI) tract, it is important to consider the functions controlled by pheromones in light of this ecology. This review summarizes our current understanding of the pCF10-encoded pheromone response. We consider how selective pressures in the natural environment may have selected for the complex and very tightly regulated systems controlling conjugation, and we pay special attention to the ecology of enterococci and the pCF10 plasmid as a gut commensal. We summarize the results of recent studies of the pheromone response at the single-cell level, as well as those of the first experiments demonstrating a role for pheromone signaling in plasmid transfer and in GI tract competitive fitness. These results will serve as a foundation for further in vivo studies that could lead to novel interventions to reduce opportunistic infections and the spread of antibiotic resistance.
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Lim SY, Teh CSJ, Thong KL. Biofilm-Related Diseases and Omics: Global Transcriptional Profiling of Enterococcus faecium Reveals Different Gene Expression Patterns in the Biofilm and Planktonic Cells. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2018; 21:592-602. [PMID: 29049010 DOI: 10.1089/omi.2017.0119] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Enterococcus faecium is an opportunistic pathogen with a remarkable ability to acquire resistance toward multiple antibiotics, including those of last-resort drugs such as vancomycin and daptomycin. The occurrence of vancomycin-resistant E. faecium is on the rise and there is a need to understand the virulence of this organism. One of the factors that contributes to the virulence is the ability to form biofilms. Since bacteria in biofilm state are more resistant to antibiotics and host immune response, understanding the molecular mechanism of biofilm development is important to control biofilm-related diseases. The aim of this study was to determine the global gene expression profiles of an E. faecium strain, VREr5, during the early event of sessile growth compared with its planktonic phase through RNA-sequencing approach. The results clearly illustrated distinct expression profiles of the planktonic and biofilm cells. A total of 177 genes were overexpressed in the biofilm cells. Most of them encode for proteins involved in adherence, such as the ebpABCfm locus. Genes associated with plasmid replication, gene exchange, and protein synthesis were also upregulated during the early event of biofilm development. Furthermore, the transcriptome analysis also identified genes such as fsrB, luxS, and spx that might suppress biofilm formation in VREr5. The putative biofilm-related bee locus was found to be downregulated. These new findings could provide caveats for future studies on the regulation and maintenance of biofilm and development of biomarkers for biofilm-related diseases.
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Affiliation(s)
- Shu Yong Lim
- 1 Institute of Biological Sciences, Faculty of Science, University of Malaya , Kuala Lumpur, Malaysia
| | - Cindy Shuan Ju Teh
- 2 Department of Medical Microbiology, Faculty of Medicine, University of Malaya , Kuala Lumpur, Malaysia
| | - Kwai Lin Thong
- 1 Institute of Biological Sciences, Faculty of Science, University of Malaya , Kuala Lumpur, Malaysia
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18
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Stochasticity in the enterococcal sex pheromone response revealed by quantitative analysis of transcription in single cells. PLoS Genet 2017; 13:e1006878. [PMID: 28671948 PMCID: PMC5515443 DOI: 10.1371/journal.pgen.1006878] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 07/18/2017] [Accepted: 06/19/2017] [Indexed: 12/23/2022] Open
Abstract
In Enterococcus faecalis, sex pheromone-mediated transfer of antibiotic resistance plasmids can occur under unfavorable conditions, for example, when inducing pheromone concentrations are low and inhibiting pheromone concentrations are high. To better understand this paradox, we adapted fluorescence in situ hybridization chain reaction (HCR) methodology for simultaneous quantification of multiple E. faecalis transcripts at the single cell level. We present direct evidence for variability in the minimum period, maximum response level, and duration of response of individual cells to a specific inducing condition. Tracking of induction patterns of single cells temporally using a fluorescent reporter supported HCR findings. It also revealed subpopulations of rapid responders, even under low inducing pheromone concentrations where the overall response of the entire population was slow. The strong, rapid induction of small numbers of cells in cultures exposed to low pheromone concentrations is in agreement with predictions of a stochastic model of the enterococcal pheromone response. The previously documented complex regulatory circuitry controlling the pheromone response likely contributes to stochastic variation in this system. In addition to increasing our basic understanding of the biology of a horizontal gene transfer system regulated by cell-cell signaling, demonstration of the stochastic nature of the pheromone response also impacts any future efforts to develop therapeutic agents targeting the system. Quantitative single cell analysis using HCR also has great potential to elucidate important bacterial regulatory mechanisms not previously amenable to study at the single cell level, and to accelerate the pace of functional genomic studies.
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19
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Gu H, Kolewe KW, Ren D. Conjugation in Escherichia coli Biofilms on Poly(dimethylsiloxane) Surfaces with Microtopographic Patterns. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3142-3150. [PMID: 28253620 DOI: 10.1021/acs.langmuir.6b04679] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Bacterial biofilms are highly tolerant to antimicrobials and play an important role in the development and spread of antibiotic resistance based on horizontal gene transfer due to close cell-to-cell contact. As an important surface property, topography has been shown to affect bacterial adhesion and biofilm formation. Here, we demonstrate that micrometer-scale surface topographies also affect horizontal gene transfer through conjugation in bacterial biofilms. Specifically, biofilm formation and associated conjugation on poly(dimethylsiloxane) (PDMS) surfaces with 10 μm tall protruding patterns were studied using fluorescently labeled donor and recipient strains of Escherichia coli. The results demonstrate that square-shaped topographic patterns with side length of 20, 50, and 100 μm and interpattern distance equal to or larger than 10 μm promote biofilm formation and conjugation compared to the smooth control. The vertical sides of these topographic features were found to be the "hot spots" for bacterial conjugation compared to the top of patterns and grooves between topographic features. The increase in conjugation frequency on the sides of topographic patterns was attributed to the high cell density of recipient cells at these locations. A motility (motB) mutant of the recipient strain exhibited defects in biofilm formation at the "hot spots" and conjugation, which were recovered by complementing the motB gene on a plasmid. These results also provided guidance for designing surface topographies that can reduce conjugation. Specifically, 10 μm tall hexagon-shaped topographic patterns with side length of 15 μm and interpattern distance of 2 μm were prepared to reduce biofilm formation on the side of protruding patterns and interrupt cell-cell interaction in the grooves. This topography exhibited 85% and 46% reduction of biofilm formation and associated conjugation, respectively, compared to the smooth control.
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Affiliation(s)
- Huan Gu
- Department of Biomedical and Chemical Engineering, ‡Syracuse Biomaterials Institute, §Department of Civil and Environmental Engineering, and ∥Department of Biology, Syracuse University , Syracuse, New York 13244, United States
| | - Kristopher W Kolewe
- Department of Biomedical and Chemical Engineering, ‡Syracuse Biomaterials Institute, §Department of Civil and Environmental Engineering, and ∥Department of Biology, Syracuse University , Syracuse, New York 13244, United States
| | - Dacheng Ren
- Department of Biomedical and Chemical Engineering, ‡Syracuse Biomaterials Institute, §Department of Civil and Environmental Engineering, and ∥Department of Biology, Syracuse University , Syracuse, New York 13244, United States
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20
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Conwell M, Daniels V, Naughton PJ, Dooley JSG. Interspecies transfer of vancomycin, erythromycin and tetracycline resistance among Enterococcus species recovered from agrarian sources. BMC Microbiol 2017; 17:19. [PMID: 28100194 PMCID: PMC5241992 DOI: 10.1186/s12866-017-0928-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 01/09/2017] [Indexed: 11/10/2022] Open
Abstract
Background Enterococci are now well recognised for their ability to transfer antibiotic resistance and for their association with nosocomial infections, but less is known regarding their relevance in the wider environment. Enterococcus faecalis and Enterococcus faecium were isolated from a range of agrarian associated sources (low-flow water, septic tank, poultry litter, high flow water, slurry/soil) and were assessed for latent ability to transfer antimicrobial resistance. Results The isolates were tested for phenotypic clumping in the presence of cell-free supernatant from other isolates. Some isolates were identified which demonstrated clumping, indicating that they possessed peptide sex pheromone conjugal machinery. All isolates were also tested for antibiotic resistance phenotypes using both disc diffusion and minimum inhibitory concentration (MIC) assays. These tests revealed that the enterococci demonstrated both phenotypic clumping and antibiotic resistance phenotypes. Based on these selection criteria, the isolates were identified as having the potential for horizontal gene transfer and were used to investigate the transfer of multiple antibiotic resistance phenotypes. Conjugal transfer of antibiotic resistance phenotypes was determined using a solid agar mating method followed by a standard antibiotic selection test resulting in different transfer patterns. An interspecies conjugal transfer of vancomycin resistance from E. faecalis to E. faecium was identified while the remaining reactions were within the same species. Transfer efficiencies ranging from 2 × 10−1 to 2.3 × 10−5 were determined based on the reactions of three donor isolates (MF06036, MF0410 and MF06035) and two recipient isolates (MW01105Rif and ST01109Rif), with the transfer of vancomycin, erythromycin and tetracycline resistance genes. Conclusions The conjugation reactions and selection conditions used in this study resulted in a variety of co-transferred resistance phenotypes suggesting the presence of different mobile elements in the set of natural isolates. This study highlights the potential for extensive horizontal gene transfer in a previously neglected reservoir for enterococci.
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Affiliation(s)
- M Conwell
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, BT52 1SA, UK
| | - V Daniels
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, BT52 1SA, UK
| | - P J Naughton
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, BT52 1SA, UK.
| | - J S G Dooley
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine, BT52 1SA, UK
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21
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Bhatty M, Camacho MI, Gonzalez-Rivera C, Frank KL, Dale JL, Manias DA, Dunny GM, Christie PJ. PrgU: a suppressor of sex pheromone toxicity in Enterococcus faecalis. Mol Microbiol 2016; 103:398-412. [PMID: 27785854 DOI: 10.1111/mmi.13563] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Upon sensing of the peptide pheromone cCF10, Enterococcus faecalis cells carrying pCF10 produce three surface adhesins (PrgA, PrgB or Aggregation Substance, PrgC) and the Prg/Pcf type IV secretion system and, in turn, conjugatively transfer the plasmid at high frequencies to recipient cells. Here, we report that cCF10 induction is highly toxic to cells sustaining a deletion of prgU, a small orf located immediately downstream of prgB on pCF10. Upon pheromone exposure, these cells overproduce the Prg adhesins and display impaired envelope integrity, as evidenced by antibiotic susceptibility, misplaced division septa and cell lysis. Compensatory mutations in regulatory loci controlling expression of pCF10-encoded prg/pcf genes, or constitutive PrgU overproduction, block production of the Prg adhesins and render cells insensitive to pheromone. Cells engineered to overproduce PrgB, even independently of other pCF10-encoded proteins, have severely compromised cell envelopes and strong growth defects. PrgU has an RNA-binding fold, and prgB-prgU gene pairs are widely distributed among E. faecalis isolates and other enterococcal and staphylococcal species. Together, our findings support a model in which PrgU proteins represent a novel class of RNA-binding regulators that act to mitigate toxicity accompanying overproduction of PrgB-like adhesins in E. faecalis and other clinically-important Gram-positive species.
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Affiliation(s)
- Minny Bhatty
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St, Houston, Texas, 77030, USA
| | - Martha I Camacho
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St, Houston, Texas, 77030, USA
| | - Christian Gonzalez-Rivera
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St, Houston, Texas, 77030, USA
| | - Kristi L Frank
- Department of Microbiology and Immunology, University of Minnesota Medical School, Microbiology Research Facility, 689 23rd Ave, S.E, Minneapolis, Minnesota, 55455, USA
| | - Jennifer L Dale
- Department of Microbiology and Immunology, University of Minnesota Medical School, Microbiology Research Facility, 689 23rd Ave, S.E, Minneapolis, Minnesota, 55455, USA
| | - Dawn A Manias
- Department of Microbiology and Immunology, University of Minnesota Medical School, Microbiology Research Facility, 689 23rd Ave, S.E, Minneapolis, Minnesota, 55455, USA
| | - Gary M Dunny
- Department of Microbiology and Immunology, University of Minnesota Medical School, Microbiology Research Facility, 689 23rd Ave, S.E, Minneapolis, Minnesota, 55455, USA
| | - Peter J Christie
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St, Houston, Texas, 77030, USA
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22
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Barnes AMT, Dale JL, Chen Y, Manias DA, Greenwood Quaintance KE, Karau MK, Kashyap PC, Patel R, Wells CL, Dunny GM. Enterococcus faecalis readily colonizes the entire gastrointestinal tract and forms biofilms in a germ-free mouse model. Virulence 2016; 8:282-296. [PMID: 27562711 DOI: 10.1080/21505594.2016.1208890] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The mammalian gastrointestinal (GI) tract is a complex organ system with a twist-a significant portion of its composition is a community of microbial symbionts. The microbiota plays an increasingly appreciated role in many clinically-relevant conditions. It is important to understand the details of biofilm development in the GI tract since bacteria in this state not only use biofilms to improve colonization, biofilm bacteria often exhibit high levels of resistance to common, clinically relevant antibacterial drugs. Here we examine the initial colonization of the germ-free murine GI tract by Enterococcus faecalis-one of the first bacterial colonizers of the naïve mammalian gut. We demonstrate strong morphological similarities to our previous in vitro E. faecalis biofilm microcolony architecture using 3 complementary imaging techniques: conventional tissue Gram stain, immunofluorescent imaging (IFM) of constitutive fluorescent protein reporter expression, and low-voltage scanning electron microscopy (LV-SEM). E. faecalis biofilm microcolonies were readily identifiable throughout the entire lower GI tract, from the duodenum to the colon. Notably, biofilm development appeared to occur as discrete microcolonies directly attached to the epithelial surface rather than confluent sheets of cells throughout the GI tract even in the presence of high (>109) fecal bacterial loads. An in vivo competition experiment using a pool of 11 select E. faecalis mutant strains containing sequence-defined transposon insertions showed the potential of this model to identify genetic factors involved in E. faecalis colonization of the murine GI tract.
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Affiliation(s)
- Aaron M T Barnes
- a Departments of Microbiology & Immunology , University of Minnesota Medical School , Minneapolis , MN , USA
| | - Jennifer L Dale
- a Departments of Microbiology & Immunology , University of Minnesota Medical School , Minneapolis , MN , USA
| | - Yuqing Chen
- a Departments of Microbiology & Immunology , University of Minnesota Medical School , Minneapolis , MN , USA
| | - Dawn A Manias
- a Departments of Microbiology & Immunology , University of Minnesota Medical School , Minneapolis , MN , USA
| | - Kerryl E Greenwood Quaintance
- b Department of Laboratory Medicine and Pathology , Division of Clinical Microbiology, Mayo Clinic , Rochester , MN , USA
| | - Melissa K Karau
- b Department of Laboratory Medicine and Pathology , Division of Clinical Microbiology, Mayo Clinic , Rochester , MN , USA
| | - Purna C Kashyap
- c Division of Gastroenterology , Department of Medicine , Mayo Clinic , Rochester , MN , USA
| | - Robin Patel
- b Department of Laboratory Medicine and Pathology , Division of Clinical Microbiology, Mayo Clinic , Rochester , MN , USA.,d Department of Medicine , Division of Infectious Disease, Mayo Clinic , Rochester , MN , USA
| | - Carol L Wells
- a Departments of Microbiology & Immunology , University of Minnesota Medical School , Minneapolis , MN , USA.,e Laboratory Medicine and Pathology , University of Minnesota Medical School , Minneapolis , MN , USA
| | - Gary M Dunny
- a Departments of Microbiology & Immunology , University of Minnesota Medical School , Minneapolis , MN , USA
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23
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Antagonistic Donor Density Effect Conserved in Multiple Enterococcal Conjugative Plasmids. Appl Environ Microbiol 2016; 82:4537-45. [PMID: 27208137 DOI: 10.1128/aem.00363-16] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/11/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Enterococcus faecalis, a common causative agent of hospital-acquired infections, is resistant to many known antibiotics. Its ability to acquire and transfer resistance genes and virulence determinants through conjugative plasmids poses a serious concern for public health. In some cases, induction of transfer of E. faecalis plasmids results from peptide pheromones produced by plasmid-free recipient cells, which are sensed by the plasmid-bearing donor cells. These plasmids generally encode an inhibitory peptide that competes with the pheromone and suppresses self-induction of donors. We recently demonstrated that the inhibitor peptide encoded on plasmid pCF10 is part of a unique quorum-sensing system in which it functions as a "self-sensing signal," reducing the response to the pheromone in a density-dependent fashion. Based on the similarities between regulatory features controlling conjugation in pAD1 and pAM373 and those controlling conjugation in pCF10, we hypothesized that these plasmids are likely to exhibit similar quorum-sensing behaviors. Experimental findings indicate that for both pAD1 and pAM373, high donor densities indeed resulted in decreased induction of the conjugation operon and reduced conjugation frequencies. This effect was restored by the addition of exogenous inhibitor, confirming that the inhibitor serves as an indicator for donor density. Donor density also affects cross-species conjugative plasmid transfer. Based on our experimental results, we propose models for induction and shutdown of the conjugation operon in pAD1 and pAM373. IMPORTANCE Enterococcus faecalis is a leading cause of hospital-acquired infections. Its ability to transfer antibiotic resistance and virulence determinants by sharing its genetic material with other bacteria through direct cell-cell contact via conjugation poses a serious threat. Two antagonistic signaling peptides control the transfer of plasmids pAD1 and pAM373: a peptide pheromone produced by plasmid-free recipients triggers the conjugative transfer in plasmid-containing donors, and an inhibitor peptide encoded on the plasmid and produced by donor cells serves to modulate the donor response in accordance with the relative abundance of donors and recipients. We demonstrate that high donor density reduces the conjugation frequency of both of these plasmids, which is a consequence of increased inhibitor concentration in high-donor-density cultures. While most antibiotic strategies end up selecting resistant strains and disrupting the community balance, manipulating bacterial signaling mechanisms can serve as an alternate strategy to prevent the spread of antibiotic resistance.
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Abstract
Conjugative transfer is the most important means of spreading antibiotic resistance and virulence factors among bacteria. The key vehicles of this horizontal gene transfer are a group of mobile genetic elements, termed conjugative plasmids. Conjugative plasmids contain as minimum instrumentation an origin of transfer (oriT), DNA-processing factors (a relaxase and accessory proteins), as well as proteins that constitute the trans-envelope transport channel, the so-called mating pair formation (Mpf) proteins. All these protein factors are encoded by one or more transfer (tra) operons that together form the DNA transport machinery, the Gram-positive type IV secretion system. However, multicellular Gram-positive bacteria belonging to the streptomycetes appear to have evolved another mechanism for conjugative plasmid spread reminiscent of the machinery involved in bacterial cell division and sporulation, which transports double-stranded DNA from donor to recipient cells. Here, we focus on the protein key players involved in the plasmid spread through the two different modes and present a new secondary structure homology-based classification system for type IV secretion protein families. Moreover, we discuss the relevance of conjugative plasmid transfer in the environment and summarize novel techniques to visualize and quantify conjugative transfer in situ.
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25
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Bhatty M, Cruz MR, Frank KL, Gomez JAL, Andrade F, Garsin DA, Dunny GM, Kaplan HB, Christie PJ. Enterococcus faecalis pCF10-encoded surface proteins PrgA, PrgB (aggregation substance) and PrgC contribute to plasmid transfer, biofilm formation and virulence. Mol Microbiol 2014; 95:660-77. [PMID: 25431047 DOI: 10.1111/mmi.12893] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2014] [Indexed: 01/24/2023]
Abstract
Enterococcus faecalis pCF10 transfers at high frequencies upon pheromone induction of the prgQ transfer operon. This operon codes for three cell wall-anchored proteins - PrgA, PrgB (aggregation substance) and PrgC - and a type IV secretion system through which the plasmid is delivered to recipient cells. Here, we defined the contributions of the Prg surface proteins to plasmid transfer, biofilm formation and virulence using the Caenorhabditis elegans infection model. We report that a combination of PrgB and extracellular DNA (eDNA), but not PrgA or PrgC, was required for extensive cellular aggregation and pCF10 transfer at wild-type frequencies. In addition to PrgB and eDNA, production of PrgA was necessary for extensive binding of enterococci to abiotic surfaces and development of robust biofilms. However, although PrgB is a known virulence factor in mammalian infection models, we determined that PrgA and PrgC, but not PrgB, were required for efficient killing in the worm infection model. We propose that the pheromone-responsive, conjugative plasmids of E. faecalis have retained Prg-like surface functions over evolutionary time for attachment, colonization and robust biofilm development. In natural settings, these biofilms are polymicrobial in composition and constitute optimal environments for signal exchange, mating pair formation and widespread lateral gene transfer.
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Affiliation(s)
- Minny Bhatty
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin Street, Houston, TX, 77030, USA
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26
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Abstract
Gram-positive bacteria are leading causes of many types of human infection, including pneumonia, skin and nasopharyngeal infections, as well as urinary tract and surgical wound infections among hospitalized patients. These infections have become particularly problematic because many of the species causing them have become highly resistant to antibiotics. The role of mobile genetic elements, such as plasmids, in the dissemination of antibiotic resistance among Gram-positive bacteria has been well studied; less well understood is the role of mobile elements in the evolution and spread of virulence traits among these pathogens. While these organisms are leading agents of infection, they are also prominent members of the human commensal ecology. It appears that these bacteria are able to take advantage of the intimate association between host and commensal, via virulence traits that exacerbate infection and cause disease. However, evolution into an obligate pathogen has not occurred, presumably because it would lead to rejection of pathogenic organisms from the host ecology. Instead, in organisms that exist as both commensal and pathogen, selection has favored the development of mechanisms for variability. As a result, many virulence traits are localized on mobile genetic elements, such as virulence plasmids and pathogenicity islands. Virulence traits may occur within a minority of isolates of a given species, but these minority populations have nonetheless emerged as a leading problem in infectious disease. This chapter reviews virulence plasmids in nonsporulating Gram-positive bacteria, and examines their contribution to disease pathogenesis.
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27
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Santoro F, Vianna ME, Roberts AP. Variation on a theme; an overview of the Tn916/Tn1545 family of mobile genetic elements in the oral and nasopharyngeal streptococci. Front Microbiol 2014; 5:535. [PMID: 25368607 PMCID: PMC4202715 DOI: 10.3389/fmicb.2014.00535] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 09/25/2014] [Indexed: 11/17/2022] Open
Abstract
The oral and nasopharyngeal streptococci are a major part of the normal microbiota in humans. Most human associated streptococci are considered commensals, however, a small number of them are pathogenic, causing a wide range of diseases including oral infections such as dental caries and periodontitis and diseases at other body sites including sinusitis and endocarditis, and in the case of Streptococcus pneumoniae, meningitis. Both phenotypic and sequence based studies have shown that the human associated streptococci from the mouth and nasopharynx harbor a large number of antibiotic resistance genes and these are often located on mobile genetic elements (MGEs) known as conjugative transposons or integrative and conjugative elements of the Tn916/Tn1545 family. These MGEs are responsible for the spread of the resistance genes between streptococci and also between streptococci and other bacteria. In this review we describe the resistances conferred by, and the genetic variations between the many different Tn916-like elements found in recent studies of oral and nasopharyngeal streptococci and show that Tn916-like elements are important mediators of antibiotic resistance genes within this genus. We will also discuss the role of the oral environment and how this is conducive to the transfer of these elements and discuss the contribution of both transformation and conjugation on the transfer and evolution of these elements in different streptococci.
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Affiliation(s)
- Francesco Santoro
- Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of SienaSiena, Italy
| | - Morgana E. Vianna
- Unit of Endodontology, UCL Eastman Dental Institute, University College LondonLondon, UK
| | - Adam P. Roberts
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College LondonLondon, UK
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Abstract
The field of plasmid biology has historically focused on bacteria growing in liquid culture. Surface attached communities of bacterial biofilms have recently been understood to be the normal environment of bacteria in the natural world. Thus, studies examining plasmid replication, maintenance, and transfer in biofilms are essential for a true understanding of bacterial plasmid biology. This chapter reviews the current knowledge of the interplay between bacterial biofilms and plasmids, focusing on the role of plasmids in biofilm development and the role of biofilms in plasmid maintenance, copy number control, and transfer. The studies examined herein highlight the importance of biofilms as an important ecological niche in which bacterial plasmids play an essential role.
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Affiliation(s)
| | - Gary M. Dunny
- Department of Microbiology, University of Minnesota, 1460 Mayo Bldg., MMC196, 420 Delaware St., SE, Minneapolis MN, 55455
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29
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30
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Affiliation(s)
- Gary M. Dunny
- Department of Microbiology, University of Minnesota, Minneapolis, Minnesota 55455;
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31
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Shu CC, Chatterjee A, Hu WS, Ramkrishna D. Role of intracellular stochasticity in biofilm growth. Insights from population balance modeling. PLoS One 2013; 8:e79196. [PMID: 24232571 PMCID: PMC3827321 DOI: 10.1371/journal.pone.0079196] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 09/19/2013] [Indexed: 11/21/2022] Open
Abstract
There is increasing recognition that stochasticity involved in gene regulatory processes may help cells enhance the signal or synchronize expression for a group of genes. Thus the validity of the traditional deterministic approach to modeling the foregoing processes cannot be without exception. In this study, we identify a frequently encountered situation, i.e., the biofilm, which has in the past been persistently investigated with intracellular deterministic models in the literature. We show in this paper circumstances in which use of the intracellular deterministic model appears distinctly inappropriate. In Enterococcus faecalis, the horizontal gene transfer of plasmid spreads drug resistance. The induction of conjugation in planktonic and biofilm circumstances is examined here with stochastic as well as deterministic models. The stochastic model is formulated with the Chemical Master Equation (CME) for planktonic cells and Reaction-Diffusion Master Equation (RDME) for biofilm. The results show that although the deterministic model works well for the perfectly-mixed planktonic circumstance, it fails to predict the averaged behavior in the biofilm, a behavior that has come to be known as stochastic focusing. A notable finding from this work is that the interception of antagonistic feedback loops to signaling, accentuates stochastic focusing. Moreover, interestingly, increasing particle number of a control variable could lead to an even larger deviation. Intracellular stochasticity plays an important role in biofilm and we surmise by implications from the model, that cell populations may use it to minimize the influence from environmental fluctuation.
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Affiliation(s)
- Che-Chi Shu
- School of Chemical Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Anushree Chatterjee
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Wei-Shou Hu
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Doraiswami Ramkrishna
- School of Chemical Engineering, Purdue University, West Lafayette, Indiana, United States of America
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de la Fuente-Núñez C, Reffuveille F, Fernández L, Hancock REW. Bacterial biofilm development as a multicellular adaptation: antibiotic resistance and new therapeutic strategies. Curr Opin Microbiol 2013; 16:580-9. [PMID: 23880136 DOI: 10.1016/j.mib.2013.06.013] [Citation(s) in RCA: 495] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 06/27/2013] [Accepted: 06/28/2013] [Indexed: 12/20/2022]
Abstract
Bacteria have evolved the ability to form multicellular, surface-adherent communities called biofilms that allow survival in hostile environments. In clinical settings, bacteria are exposed to various sources of stress, including antibiotics, nutrient limitation, anaerobiosis, heat shock, etc., which in turn trigger adaptive responses in bacterial cells. The combination of this and other defense mechanisms results in the formation of highly (adaptively) resistant multicellular structures that are recalcitrant to host immune clearance mechanisms and very difficult to eradicate with the currently available antimicrobial agents, which are generally developed for the eradication of free-swimming (planktonic) bacteria. However, novel strategies that specifically target the biofilm mode of growth have been recently described, thus providing the basis for future anti-biofilm therapy.
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Affiliation(s)
- César de la Fuente-Núñez
- Centre for Microbial Diseases and Immunity Research, Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
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Effects of biofilm growth on plasmid copy number and expression of antibiotic resistance genes in Enterococcus faecalis. Antimicrob Agents Chemother 2013; 57:1850-6. [PMID: 23380728 DOI: 10.1128/aac.02010-12] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biofilm growth causes increased average plasmid copy number as well as increased copy number heterogeneity in Enterococcus faecalis cells carrying plasmid pCF10. In this study, we examined whether biofilm growth affected the copy number and expression of antibiotic resistance determinants for several plasmids with diverse replication systems. Four different E. faecalis plasmids, unrelated to pCF10, demonstrated increased copy number in biofilm cells. In biofilm cells, we also observed increased transcription of antibiotic resistance genes present on these plasmids. The increase in plasmid copy number correlated with increased plating efficiency on high concentrations of antibiotics. Single-cell analysis of strains carrying two different plasmids suggested that the increase in plasmid copy number associated with biofilm growth was restricted to a subpopulation of biofilm cells. Regrowth of harvested biofilm cells in liquid culture resulted in a rapid reduction of plasmid copy number to that observed in the planktonic state. These results suggest a possible mechanism by which biofilm growth could reduce susceptibility to antibiotics in clinical settings.
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In vivo and in vitro analyses of regulation of the pheromone-responsive prgQ promoter by the PrgX pheromone receptor protein. J Bacteriol 2012; 194:3386-94. [PMID: 22544272 DOI: 10.1128/jb.00364-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of conjugative transfer and virulence functions of the Enterococcus faecalis antibiotic resistance plasmid pCF10 is regulated by the interaction of the pheromone receptor protein PrgX with two DNA binding operator sites (XBS1 and XBS2) upstream from the transcription start site of the prgQ operon (encoding the pCF10 transfer machinery) and by posttranscriptional mechanisms. Occupancy of both binding sites by PrgX dimers results in repression of the prgQ promoter. Structural and genetic studies suggest that the peptide pheromone cCF10 functions by binding to PrgX and altering its oligomerization state, resulting in reduced occupancy of XBSs and increased prgQ transcription. The DNA binding activity of PrgX has additional indirect regulatory effects on prgQ transcript levels related to the position of the convergently transcribed prgX operon. This has complicated interpretation of previous analyses of the control of prgQ expression by PrgX. We report here the results of in vivo and in vitro experiments examining the direct effects of PrgX on transcription from the prgQ promoter, as well as quantitative correlation between the concentrations of XBSs, PrgX protein, and prgQ promoter activity in vivo. The results of electrophoretic mobility shift assays and quantitative analysis of prgQ transcription in vitro and in vivo support the predicted roles of the PrgX DNA binding sites in prgQ transcription regulation. The results also suggest the existence of other factors that impede PrgX repression or enhance its antagonism by cCF10 in vivo.
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