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Soto-Aceves MP, González-Valdez A, Cocotl-Yañez M, Soberón-Chávez G. Pseudomonas aeruginosa LasR overexpression leads to a RsaL-independent pyocyanin production inhibition in a low phosphate condition. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 36301076 DOI: 10.1099/mic.0.001262] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Several Pseudomonas aeruginosa virulence-related traits like pyocyanin are regulated by an intricate regulatory network called quorum sensing (QS) that relies on transcriptional regulators that are activated through binding to a self-produced molecule called an autoinducer (AI). QS is composed of three systems, Las, Rhl and Pqs. In the Las system, the regulatory protein LasR interacts with its AI to activate the other two QS systems. In turn, the Rhl and Pqs systems regulate the expression of multiple virulence-related genes, such as the genes of the reiterated operons phzA1B1C1D1E1F1G1 and phzA2B2C2D2E2F2G2 involved in pyocyanin production. The Las system also regulates the negative regulator RsaL, which provides negative feedback to the QS-response, including repression of pyocyanin synthesis genes. In this work, we describe that LasR can act as a negative regulator of phzA1 transcription and hence of pyocyanin production and that this regulation is independent of RsaL activity. This work contributes to the understanding of QS-dependent pyocyanin production and demonstrates a previously uncharacterized role of LasR as a repressor.
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Affiliation(s)
- Martín Paolo Soto-Aceves
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico.,Present address: Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Miguel Cocotl-Yañez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
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Abstract
Quorum sensing (QS) is used to coordinate social behaviors, such as virulence and biofilm formation, across bacterial populations. However, the role of QS in regulating phage-bacterium interactions remains unclear. Preventing phage recognition and adsorption are the first steps of bacterial defense against phages; however, both phage recognition and adsorption are a prerequisite for the successful application of phage therapy. In the present study, we report that QS upregulated the expression of phage receptors, thus increasing phage adsorption and infection rates in Pseudomonas aeruginosa. In P. aeruginosa PAO1, we found that las QS, instead of rhl QS, upregulated the expression of galU for lipopolysaccharide synthesis. Lipopolysaccharides act as the receptor of the phage vB_Pae_QDWS. This las QS-mediated phage susceptibility is a dynamic process, depending on host cell density. Our data suggest that inhibiting QS may reduce the therapeutic efficacy of phages. IMPORTANCE Phage resistance is a major limitation of phage therapy, and understanding the mechanisms by which bacteria block phage infection is critical for the successful application of phage therapy. In the present study, we found that Pseudomonas aeruginosa PAO1 uses las QS to promote phage infection by upregulating the expression of galU, which is necessary for the synthesis of phage receptor lipopolysaccharides. In contrast to the results of previous reports, we showed that QS increases the efficacy of phage-mediated bacterial killing. Since QS upregulates the expression of virulence factors and promotes biofilm development, which are positively correlated with lipopolysaccharide production in P. aeruginosa, increased phage susceptibility is a novel QS-mediated trade-off. QS inhibition may increase the efficacy of antibiotic treatment, but it will reduce the effectiveness of phage therapy.
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Zhao K, Liu L, Chen X, Huang T, Du L, Lin J, Yuan Y, Zhou Y, Yue B, Wei K, Chu Y. Behavioral heterogeneity in quorum sensing can stabilize social cooperation in microbial populations. BMC Biol 2019; 17:20. [PMID: 30841874 PMCID: PMC6889464 DOI: 10.1186/s12915-019-0639-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 02/19/2019] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Microbial communities are susceptible to the public goods dilemma, whereby individuals can gain an advantage within a group by utilizing, but not sharing the cost of producing, public goods. In bacteria, the development of quorum sensing (QS) can establish a cooperation system in a population by coordinating the production of costly and sharable extracellular products (public goods). Cooperators with intact QS system and robust ability in producing public goods are vulnerable to being undermined by QS-deficient defectors that escape from QS but benefit from the cooperation of others. Although microorganisms have evolved several mechanisms to resist cheating invasion in the public goods game, it is not clear why cooperators frequently coexist with defectors and how they form a relatively stable equilibrium during evolution. RESULTS We show that in Pseudomonas aeruginosa, QS-directed social cooperation can select a conditional defection strategy prior to the emergence of QS-mutant defectors, depending on resource availability. Conditional defectors represent a QS-inactive state of wild type (cooperator) individual and can invade QS-activated cooperators by adopting a cheating strategy, and then revert to cooperating when there are abundant nutrient supplies irrespective of the exploitation of QS-mutant defector. Our mathematical modeling further demonstrates that the incorporation of conditional defection strategy into the framework of iterated public goods game with sound punishment mechanism can lead to the coexistence of cooperator, conditional defector, and defector in a rock-paper-scissors dynamics. CONCLUSIONS These findings highlight the importance of behavioral heterogeneity in stabilizing the population structure and provide a potential reasonable explanation for the maintenance and evolution of cooperation in microbial communities.
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Affiliation(s)
- Kelei Zhao
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, No. 168, Huaguan Road, Chengdu, 610052 Sichuan China
| | - Linjie Liu
- School of Mathematical Sciences, University of Electronic Science and Technology of China, No. 2006, Xiyuan Avenue, Chengdu, 611731 Sichuan China
| | - Xiaojie Chen
- School of Mathematical Sciences, University of Electronic Science and Technology of China, No. 2006, Xiyuan Avenue, Chengdu, 611731 Sichuan China
| | - Ting Huang
- Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Sciences, Sichuan University, Chengdu, China
| | - Lianming Du
- Institute for Advanced Study, Chengdu University, Chengdu, China
| | - Jiafu Lin
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, No. 168, Huaguan Road, Chengdu, 610052 Sichuan China
| | - Yang Yuan
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, No. 168, Huaguan Road, Chengdu, 610052 Sichuan China
| | - Yingshun Zhou
- Department of Pathogenic Biology, College of Preclinical Medicine, Southwest Medical University, Luzhou, China
| | - Bisong Yue
- Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Sciences, Sichuan University, Chengdu, China
| | - Kun Wei
- School of Mathematical Sciences, University of Electronic Science and Technology of China, No. 2006, Xiyuan Avenue, Chengdu, 611731 Sichuan China
| | - Yiwen Chu
- Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province, Sichuan Industrial Institute of Antibiotics, Chengdu University, No. 168, Huaguan Road, Chengdu, 610052 Sichuan China
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Analysis of two quorum sensing-deficient isolates of Pseudomonas aeruginosa. Microb Pathog 2018; 119:162-169. [PMID: 29635051 DOI: 10.1016/j.micpath.2018.04.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 04/04/2018] [Accepted: 04/06/2018] [Indexed: 01/23/2023]
Abstract
Three strains of Pseudomonas aeruginosa were isolated: wild-type (WT, NO4) showed normal quorum sensing (QS), whereas QSD3 and QSD7 were QS-deficient (QSD) containing limited N-butyryl homoserine lactone (C4-HSL). The autoinducer activity produced by NO4 was found to be at least 50-fold higher than those by the QSD3 and the QSD7 strains. The QSDs produced lower levels of phenazine compounds (pyocyanin), siderophores (pyoverdine) and biosurfactants (rhamnolipids) than NO4. Therefore, the swarming motility and the swimming motility of the QSD3 and the QSD7 strains also decreased. Treatment with exogenous C4-HSL completely restored rhamnolipid production in both QSDs, suggesting that the biosynthesis of C4-HSL is defective. However, the biofilm production of the QSDs reached much higher levels than those of wild-types (NO4 and P. aeruginosa PAO1). And both QSD strains were more resistant than wild-type cell (NO4) against kanamycin and tobramycin. The RpoS gene, which function is related with QS, is point-nonsense mutated in QSD3 strain. But eleven QS-related genes in QSD3 were not mutated, compared to those of PAO1, which carries intact QS genes and is used as a positive control. This study is helpful in the development of novel approaches in the treatment of P. aeruginosa infections.
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Varjani SJ, Upasani VN. Critical review on biosurfactant analysis, purification and characterization using rhamnolipid as a model biosurfactant. BIORESOURCE TECHNOLOGY 2017; 232:389-397. [PMID: 28238638 DOI: 10.1016/j.biortech.2017.02.047] [Citation(s) in RCA: 172] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/08/2017] [Accepted: 02/12/2017] [Indexed: 05/15/2023]
Abstract
Surfactants are one of the most versatile group of chemicals used in various industrial processes. Their market is competitive, and manufacturers will have to expand surfactant production in ecofriendly and cost effective manner. Increasing interest in biosurfactants led to an intense research for environment friendly and cost-efficient production of biosurfactant. Structural diversity and functional properties of biosurfactants make them an attractive group of compounds for potential use in wide variety of industrial, environmental and biotechnological applications. Screening methods make task easier to obtain potential biosurfactant producing microorganisms. Variety of purification and analytical methods are available for biosurfactant structural characterization. This review aims to compile information on types and properties of biosurfactant, microbial screening methods as well as biosynthesis, extraction, purification and structural characterization of biosurfactant using rhamnolipid as a model biosurfactant. It also describes factors affecting rhamnolipid production. It gives an overview of oil recovery using biosurfactant from Pseudomonas aeruginosa.
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Affiliation(s)
- Sunita J Varjani
- Department of Microbiology, M.G. Science Institute, Ahmedabad 380009, Gujarat, India.
| | - Vivek N Upasani
- Department of Microbiology, M.G. Science Institute, Ahmedabad 380009, Gujarat, India
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Lixa C, Marques AF, Cortines JR, Neves BC, Oliveira DM, Anobom CD, Lima LMT, Pinheiro AS. Refolding, purification, and preliminary structural characterization of the DNA-binding domain of the quorum sensing receptor RhlR from Pseudomonas aeruginosa. Protein Expr Purif 2016; 121:31-40. [DOI: 10.1016/j.pep.2016.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/18/2015] [Accepted: 01/08/2016] [Indexed: 12/22/2022]
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7
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Jirku V, Cejkova A, Schreiberova O, Jezdik R, Masak J. Multicomponent biosurfactants — A “Green Toolbox” extension. Biotechnol Adv 2015; 33:1272-6. [DOI: 10.1016/j.biotechadv.2015.03.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 02/12/2015] [Accepted: 03/06/2015] [Indexed: 11/27/2022]
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8
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Grosso-Becera MV, Servín-González L, Soberón-Chávez G. RNA structures are involved in the thermoregulation of bacterial virulence-associated traits. Trends Microbiol 2015; 23:509-18. [PMID: 25999019 DOI: 10.1016/j.tim.2015.04.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/01/2015] [Accepted: 04/16/2015] [Indexed: 11/25/2022]
Abstract
Pathogenic bacteria are exposed to temperature changes during colonization of the human body and during exposure to environmental conditions. Virulence-associated traits are mainly expressed by pathogenic bacteria at 37°C. We review different cases of post-transcriptional regulation of virulence-associated proteins through RNA structures (called RNA thermometers or RNATs) that modulate the translation of mRNAs. The analysis of RNATs in pathogenic bacteria has started to produce a comprehensive picture of the structures involved, and of the genes regulated by this mechanism. However, we are still not able to predict the functionality of putative RNATs predicted by bioinformatics methods, and there is not a global approach to measure the effect of these RNA structures in gene regulation during bacterial infections.
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Affiliation(s)
- María Victoria Grosso-Becera
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones, Biomédicas, Universidad Nacional Autónoma de México, Tercer Circuito Escolar, Apartado Postal 70228, DF, México
| | - Luis Servín-González
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones, Biomédicas, Universidad Nacional Autónoma de México, Tercer Circuito Escolar, Apartado Postal 70228, DF, México
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones, Biomédicas, Universidad Nacional Autónoma de México, Tercer Circuito Escolar, Apartado Postal 70228, DF, México.
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9
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González-Valdez A, Servín-González L, Juárez K, Hernandez-Aligio A, Soberón-Chávez G. The effect of specific rhlA-las-box mutations on DNA binding and gene activation by Pseudomonas aeruginosa quorum-sensing transcriptional regulators RhlR and LasR. FEMS Microbiol Lett 2015; 356:217-25. [PMID: 24935161 DOI: 10.1111/1574-6968.12505] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 06/05/2014] [Accepted: 06/07/2014] [Indexed: 01/22/2023] Open
Abstract
Pseudomonas aeruginosa is a free-living bacterium and an important opportunistic pathogen. The genes coding for virulence-associated traits are regulated at the level of transcription by the quorum-sensing response. In this response, the regulator LasR coupled with the autoinducer 3-oxo-dodecanoyl homoserine lactone (3O-C12-HSL) activates transcription of genes for several virulence factors. LasR/3O-C12-HSL also activates transcription of rhlR, the gene coding for the transcriptional regulator RhlR, and of rhlI that encodes the synthase that produces the autoinducer butanoyl-homoserine lactone (C4-HSL) that interacts with RhlR. Genes activated by RhlR/C4-HSL include those involved in rhamnolipids production (like the rhlAB operon) and lecA, coding for PA-I lectin. The molecular basis of LasR/3O-C12-HSL- and RhlR/C4-HSLDNA-binding specificity (at the so-called las-boxes) has not been clearly determined, and the aim of this work was to contribute to its understanding. Therefore, we analyzed the interaction of LasR and RhlR to variants of the rhlA-las-box that were constructed based on the comparison of this las-box to the las-box of lecA. We conclude that LasR and RhlR DNA-binding specificity is a complex multifactorial phenomenon in which both positive and negative effects are involved and that binding of these proteins does not necessarily result in gene activation.
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Affiliation(s)
- Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, México
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10
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Kinetic modeling of rhamnolipid production by Pseudomonas aeruginosa PAO1 including cell density-dependent regulation. Appl Microbiol Biotechnol 2014; 98:7013-25. [DOI: 10.1007/s00253-014-5750-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/02/2014] [Accepted: 04/02/2014] [Indexed: 10/25/2022]
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11
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Longo F, Rampioni G, Bondì R, Imperi F, Fimia GM, Visca P, Zennaro E, Leoni L. A new transcriptional repressor of the pseudomonas aeruginosa quorum sensing receptor gene lasR. PLoS One 2013; 8:e69554. [PMID: 23861975 PMCID: PMC3702619 DOI: 10.1371/journal.pone.0069554] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/10/2013] [Indexed: 12/25/2022] Open
Abstract
Pseudomonas aeruginosa pathogenic potential is controlled via multiple regulatory pathways, including three quorum sensing (QS) systems. LasR is a key QS signal receptor since it acts as a global transcriptional regulator required for optimal expression of main virulence factors. P. aeruginosa modulates the QS response by integrating this cell density-dependent circuit to environmental and metabolic cues. Hence, QS also controls the adaptation to challenging environmental niches, such as infection sites. However, little is known about the molecular mechanisms connecting QS and other signalling pathways. In this work, DNA-affinity chromatography was used to identify new lasR transcriptional regulators. This approach led to the identification and functional characterization of the TetR-like transcriptional repressor PA3699. This protein was purified and shown to directly bind to the lasR promoter region in vitro. The induction of PA3699 expression in P. aeruginosa PAO1 cultures repressed lasR promoter activity and the production of LasR-dependent virulence factors, such as elastase, pyocyanin, and proteases. These findings suggest a role for PA3699 in P. aeruginosa pathogenicity. P. aeruginosa genome encodes at least 38 TetR-family proteins, and PA3699 is the eighth member of this group functionally characterized so far and the first one shown to bind the lasR promoter in vitro.
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Henkel M, Schmidberger A, Kühnert C, Beuker J, Bernard T, Schwartz T, Syldatk C, Hausmann R. Kinetic modeling of the time course of N-butyryl-homoserine lactone concentration during batch cultivations of Pseudomonas aeruginosa PAO1. Appl Microbiol Biotechnol 2013; 97:7607-16. [PMID: 23780585 DOI: 10.1007/s00253-013-5024-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Revised: 05/27/2013] [Accepted: 05/28/2013] [Indexed: 11/26/2022]
Abstract
Quorum sensing affects the regulation of more than 300 genes in Pseudomonas aeruginosa, influencing growth, biofilm formation, and the biosynthesis of several products. The quorum sensing regulation mechanisms are mostly described in a qualitative character. Particularly, in this study, the kinetics of N-butyryl-homoserine lactone (C4-HSL) and rhamnolipid formation in P. aeruginosa PAO1 were of interest. In this system, the expression of the rhamnolipid biosynthesis genes rhlAB is directly coupled to the C4-HSL concentration via the rhl system. Batch cultivations in a bioreactor with sunflower oil have been used for these investigations. 3-oxo-dodecanoyl-homoserine lactone (3o-C12-HSL) displayed a lipophilic character and accumulated in the hydrophobic phase. Degradation of C4-HSL has been found to occur in the aqueous supernatant of the culture by yet unknown extracellular mechanisms, and production was found to be proportional to biomass concentration rather than by autoinduction mechanisms. Rhamnolipid production rates, as determined experimentally, were shown to correlate linearly with the concentration of autoinducer C4-HSL. These findings were used to derive a simple model, wherein a putative, extracellular protein with C4-HSL degrading activity was assumed (putative C4-HSL acylase). The model is based on data for catalytic efficiency of HSL-acylases extracted from literature (k cat/K m), experimentally determined basal C4-HSL production rates (q C4 - HSL (basal)), and two fitted parameters which describe the formation of the putative acylase and is therefore comparatively simple.
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Affiliation(s)
- Marius Henkel
- Institute of Process Engineering in Life Sciences, Section II: Technical Biology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131, Karlsruhe, Germany.
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13
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Müller MM, Kügler JH, Henkel M, Gerlitzki M, Hörmann B, Pöhnlein M, Syldatk C, Hausmann R. Rhamnolipids—Next generation surfactants? J Biotechnol 2012; 162:366-80. [DOI: 10.1016/j.jbiotec.2012.05.022] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Revised: 05/06/2012] [Accepted: 05/18/2012] [Indexed: 12/26/2022]
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14
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Agarwal A, Kahyaoglu C, Hansen DB. Characterization of HmqF, a Protein Involved in the Biosynthesis of Unsaturated Quinolones Produced by Burkholderia thailandensis. Biochemistry 2012; 51:1648-57. [DOI: 10.1021/bi201625w] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Aparna Agarwal
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
| | - Caroline Kahyaoglu
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
| | - Darren B. Hansen
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
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Aguirre-Ramírez M, Medina G, González-Valdez A, Grosso-Becerra V, Soberón-Chávez G. The Pseudomonas aeruginosa rmlBDAC operon, encoding dTDP-L-rhamnose biosynthetic enzymes, is regulated by the quorum-sensing transcriptional regulator RhlR and the alternative sigma factor σS. MICROBIOLOGY-SGM 2012; 158:908-916. [PMID: 22262098 DOI: 10.1099/mic.0.054726-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pseudomonas aeruginosa produces as biosurfactants rhamnolipids, containing one (mono-rhamnolipid) or two (di-rhamnolipid) l-rhamnose molecules. The rhamnosyltransferase RhlB catalyses the synthesis of mono-rhamnolipid using as precursors dTDP-l-rhamnose and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) produced by RhlA, while the rhamnosyltransferase RhlC synthesizes di-rhamnolipid using mono-rhamnolipid and dTDP-l-rhamnose as substrates. The Las and Rhl quorum-sensing systems coordinately regulate the production of these surfactants, as well as that of other exoproducts involved in bacterial virulence, at the transcriptional level in a cell density-dependent manner. In this work we study the transcriptional regulation of the rmlBDAC operon, encoding the enzymes involved in the production of dTDP-l-rhamnose, the substrate of both rhamnosyltransferases, RhlB and RhlC, and also a component of P. aeruginosa lipopolysaccharide. Here we show that the rmlBDAC operon possesses three promoters. One of these transcriptional start sites (P2) is responsible for most of its expression and is dependent on the stationary phase sigma factor σ(S) and on RhlR/C(4)-HSL through its binding to an atypical 'las box'.
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Affiliation(s)
- Marisela Aguirre-Ramírez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
| | - Gerardo Medina
- Universidad Autónoma de Baja California, Mexicali, BC, México
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
| | - Victoria Grosso-Becerra
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
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Croda-García G, Grosso-Becerra V, Gonzalez-Valdez A, Servín-González L, Soberón-Chávez G. Transcriptional regulation of Pseudomonas aeruginosa rhlR: role of the CRP orthologue Vfr (virulence factor regulator) and quorum-sensing regulators LasR and RhlR. MICROBIOLOGY-SGM 2011; 157:2545-2555. [PMID: 21719541 DOI: 10.1099/mic.0.050161-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The production of many virulence factors by Pseudomonas aeruginosa is regulated by the quorum-sensing (QS) response. In this regulatory network LasR and RhlR, bound to their corresponding autoinducers, play a central role. The QS response has a hierarchical structure: LasR/3O-C12-HSL activates the transcription of rhlR, and RhlR/C4-HSL activates the transcription of several genes, including the rhlAB operon, which encodes the enzymes responsible for rhamnolipid synthesis. The rhlAB operon is located immediately upstream of the rhlR gene. rhlR has four transcription start sites, two of which are located in the rhlB coding region. Vfr directly activates transcription of lasR, and has been reported to be also involved in rhlR expression. The aim of this work was to characterize the details of the mechanism of rhlR transcriptional regulation. We show that Vfr directly regulates rhlR transcription through its binding to several Vfr-binding sites (VBSs) present in the rhlR promoter region, one of which has a negative effect on transcription. Two of the VBSs overlap with las boxes where LasR/3O-C12-HSL binds to activate rhlR transcription. We also show that rhlR transcription is subject to positive-feedback autoregulation through RhlR/C4-HSL activation of the rhlA promoter. This positive autoregulation plays a major role in rhlR expression.
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Affiliation(s)
- Gerardo Croda-García
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico
| | - Victoria Grosso-Becerra
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico
| | - Abigail Gonzalez-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico
| | - Luis Servín-González
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal 70228, México DF 04510, Mexico
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Kalia VC, Purohit HJ. Quenching the quorum sensing system: potential antibacterial drug targets. Crit Rev Microbiol 2011; 37:121-40. [PMID: 21271798 DOI: 10.3109/1040841x.2010.532479] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Emergence of antibiotic and multi-drug resistant pathogenic bacteria has created the need for new drugs and drug targets. During pathogenesis bacteria release signals which regulate virulence and pathogenicity related genes. Such bacteria co-ordinate their virulent behaviour in a cell density dependent phenomenon termed as quorum sensing (QS). In contrast, microbes interfere with QS system by quenching the signals, termed quorum quenching (QQ). As a consequence of disrupted QS, pathogens become susceptible to antibiotics and drugs. In this article, the biodiversity of organisms with potential to quench QS signals and the use of QQ molecules as antibacterial drugs have been reviewed.
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Affiliation(s)
- Vipin Chandra Kalia
- Microbial Biotechnology and Genomics, Institute of Genomics and Integrative Biology (IGIB), CSIR, Delhi University Campus, Mall Road, Delhi-110007, India.
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18
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Quorum sensing inhibitory drugs as next generation antimicrobials: worth the effort? Curr Infect Dis Rep 2010; 10:22-8. [PMID: 18377811 DOI: 10.1007/s11908-008-0006-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Bacterial resistance poses a major challenge to the development of new antimicrobial agents. Conventional antibiotics have an inherent obsolescence because they select for development of resistance. Bacterial infections have again become a serious threat in developed countries. Particularly, elderly, immunocompromised, and hospitalized patients are susceptible to infections caused by bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. These bacteria form chronic, biofilm-based infections, which are challenging because bacterial cells living as biofilms are more tolerant to antibiotics than their planktonic counterparts. Therefore, research should identify new antimicrobial agents and their corresponding targets to decrease the biofilm-forming capability or persistence of the infectious bacteria. Here, we review one such drug target: bacterial cell-to-cell communication systems, or quorum sensing.
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Hazan R, He J, Xiao G, Dekimpe V, Apidianakis Y, Lesic B, Astrakas C, Déziel E, Lépine F, Rahme LG. Homeostatic interplay between bacterial cell-cell signaling and iron in virulence. PLoS Pathog 2010; 6:e1000810. [PMID: 20300606 PMCID: PMC2837411 DOI: 10.1371/journal.ppat.1000810] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 02/05/2010] [Indexed: 12/28/2022] Open
Abstract
Pathogenic bacteria use interconnected multi-layered regulatory networks, such as quorum sensing (QS) networks to sense and respond to environmental cues and external and internal bacterial cell signals, and thereby adapt to and exploit target hosts. Despite the many advances that have been made in understanding QS regulation, little is known regarding how these inputs are integrated and processed in the context of multi-layered QS regulatory networks. Here we report the examination of the Pseudomonas aeruginosa QS 4-hydroxy-2-alkylquinolines (HAQs) MvfR regulatory network and determination of its interaction with the QS acyl-homoserine-lactone (AHL) RhlR network. The aim of this work was to elucidate paradigmatically the complex relationships between multi-layered regulatory QS circuitries, their signaling molecules, and the environmental cues to which they respond. Our findings revealed positive and negative homeostatic regulatory loops that fine-tune the MvfR regulon via a multi-layered dependent homeostatic regulation of the cell-cell signaling molecules PQS and HHQ, and interplay between these molecules and iron. We discovered that the MvfR regulon component PqsE is a key mediator in orchestrating this homeostatic regulation, and in establishing a connection to the QS rhlR system in cooperation with RhlR. Our results show that P. aeruginosa modulates the intensity of its virulence response, at least in part, through this multi-layered interplay. Our findings underscore the importance of the homeostatic interplay that balances competition within and between QS systems via cell-cell signaling molecules and environmental cues in the control of virulence gene expression. Elucidation of the fine-tuning of this complex relationship offers novel insights into the regulation of these systems and may inform strategies designed to limit infections caused by P. aeruginosa and related human pathogens. Bacterial cells can communicate with one another about their surrounding environment. This information can be in the form of small self-secreted molecules acting as signals to activate or inhibit the expression of genes. Pseudomonas aeruginosa is an environmental bacterium that infects diverse organisms from plants to humans. Our results show that this pathogen uses two highly sensitive networks, namely MvfR and LasR/RhlR pathways, to modulate its virulence functions by titrating the concentration of the small molecules HHQ and PQS in a manner that depends upon the presence or absence of iron. Via negative and positive feedback loops, this bacterium processes the signaled information to regulate its virulence functions and homeostatically balance the production of the small molecules required for the activation of the MvfR virulence network. Our study sheds light on paradigmatic complex networks that maintain a homeostatic bacterial virulence response.
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Affiliation(s)
- Ronen Hazan
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jianxin He
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Gaoping Xiao
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | | | - Yiorgos Apidianakis
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Biliana Lesic
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Christos Astrakas
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Eric Déziel
- INRS-Institut Armand-Frappier, Laval, Québec, Canada
| | | | - Laurence G. Rahme
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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Satpute SK, Bhuyan SS, Pardesi KR, Mujumdar SS, Dhakephalkar PK, Shete AM, Chopade BA. Molecular Genetics of Biosurfactant Synthesis in Microorganisms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 672:14-41. [DOI: 10.1007/978-1-4419-5979-9_2] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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21
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Cha M, Lee N, Kim M, Kim M, Lee S. Heterologous production of Pseudomonas aeruginosa EMS1 biosurfactant in Pseudomonas putida. BIORESOURCE TECHNOLOGY 2008; 99:2192-9. [PMID: 17611103 DOI: 10.1016/j.biortech.2007.05.035] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 05/14/2007] [Accepted: 05/15/2007] [Indexed: 05/16/2023]
Abstract
A new bacterial strain isolated from activated sludge, identified as Pseudomonas aeruginosa EMS1, produced a biosurfactant when grown on acidified soybean oil as the sole carbon source. An optimum biosurfactant production of 5 g/L was obtained with the following medium composition: 2% acidified soybean oil, 0.3% NH4NO3, 0.03% KH2PO4, 0.03% K2HPO4, 0.02% MgSO4.7H2O and 0.025% CaCl2.2H2O, with shaking at 200 rpm for an incubation period of 100 h at 30 degrees C. The production of the biosurfactant was found to be a function of cell growth, with maximum production occurring during the exponential phase. Hemolysis of erythrocytes and thin-layer chromatography studies revealed that the secreted biosurfactant was rhamnolipid. To overcome the complex environmental regulation with respect to rhamnolipid biosynthesis, and to replace the opportunistic pathogen P. aeruginosa with a safe industrial strain, attempts were made to achieve rhamnolipid production in a heterologous host, Pseudomonas putida, using molecular cloning of rhlAB rhamnosyltransferase genes with the rhlRI quorum sensing system, assuming that a functional rhamnosyltransferase would catalyze the formation of rhamnosyl-6-hydroxydecanoyl-6-hydroxydecanoate (mono-rhamnolipid) in P. putida. It was shown that rhamnolipid can be produced in the heterologous strain, P. putida, when provided with the rhamnosyltransferase genes.
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Affiliation(s)
- Misun Cha
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Republic of Korea
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22
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Shapiro JA. Bacteria are small but not stupid: cognition, natural genetic engineering and socio-bacteriology. STUDIES IN HISTORY AND PHILOSOPHY OF BIOLOGICAL AND BIOMEDICAL SCIENCES 2007; 38:807-819. [PMID: 18053935 DOI: 10.1016/j.shpsc.2007.09.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Forty years' experience as a bacterial geneticist has taught me that bacteria possess many cognitive, computational and evolutionary capabilities unimaginable in the first six decades of the twentieth century. Analysis of cellular processes such as metabolism, regulation of protein synthesis, and DNA repair established that bacteria continually monitor their external and internal environments and compute functional outputs based on information provided by their sensory apparatus. Studies of genetic recombination, lysogeny, antibiotic resistance and my own work on transposable elements revealed multiple widespread bacterial systems for mobilizing and engineering DNA molecules. Examination of colony development and organization led me to appreciate how extensive multicellular collaboration is among the majority of bacterial species. Contemporary research in many laboratories on cell-cell signaling, symbiosis and pathogenesis show that bacteria utilise sophisticated mechanisms for intercellular communication and even have the ability to commandeer the basic cell biology of 'higher' plants and animals to meet their own needs. This remarkable series of observations requires us to revise basic ideas about biological information processing and recognise that even the smallest cells are sentient beings.
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Affiliation(s)
- J A Shapiro
- Department of Biochemistry and Molecular Biology, University of Chicago, 929 E. 57th Street, Chicago IL 60637, USA.
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Alibaud L, Köhler T, Coudray A, Prigent-Combaret C, Bergeret E, Perrin J, Benghezal M, Reimmann C, Gauthier Y, van Delden C, Attree I, Fauvarque MO, Cosson P. Pseudomonas aeruginosa virulence genes identified in a Dictyostelium host model. Cell Microbiol 2007; 10:729-40. [PMID: 18042255 DOI: 10.1111/j.1462-5822.2007.01080.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The human pathogen Pseudomonas aeruginosa has been shown previously to use similar virulence factors when infecting mammalian hosts or Dictyostelium amoebae. Here we randomly mutagenized a clinical isolate of P. aeruginosa, and identified mutants with attenuated virulence towards Dictyostelium. These mutant strains also exhibited a strong decrease in virulence when infecting Drosophila and mice, confirming that P. aeruginosa makes use of similar virulence traits to confront these very different hosts. Further characterization of these bacterial mutants showed that TrpD is important for the induction of the quorum-sensing circuit, while PchH and PchI are involved in the induction of the type III secretion system. These results demonstrate the usefulness and the relevance of the Dictyostelium host model to identify and analyse new virulence genes in P. aeruginosa.
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Affiliation(s)
- Laeticia Alibaud
- Département de Physiologie Cellulaire et Métabolisme, Université de Genève, Centre Médeical Universitaire, 1 rue Michel Servet, CH-1211 Geneva 4, Switzerland
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24
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Wang Q, Fang X, Bai B, Liang X, Shuler PJ, Goddard WA, Tang Y. Engineering bacteria for production of rhamnolipid as an agent for enhanced oil recovery. Biotechnol Bioeng 2007; 98:842-53. [PMID: 17486652 DOI: 10.1002/bit.21462] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.
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Affiliation(s)
- Qinhong Wang
- Power, Energy and Environment Research (PEER) Center, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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Duan K, Surette MG. Environmental regulation of Pseudomonas aeruginosa PAO1 Las and Rhl quorum-sensing systems. J Bacteriol 2007; 189:4827-36. [PMID: 17449617 PMCID: PMC1913434 DOI: 10.1128/jb.00043-07] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The lasI-lasR and the rhlI-rhlR quorum-sensing systems in Pseudomonas aeruginosa regulate the expression of numerous cellular and secreted virulence factor genes and play important roles in the development of biofilms. The las and rhl systems themselves are known to be directly or indirectly regulated by a number of transcriptional regulators, and consequently, their expression is sensitive to environmental conditions. In this report, the activities of these two quorum-sensing systems have been examined systematically under 46 growth conditions, and the regulation by environmental conditions has been investigated. The relative timing and strength of expression of these two systems varied significantly under different conditions, which contrasts with the notion of a preset hierarchy with these two systems in P. aeruginosa. Depending on the growth conditions, the correlation between each synthase and its cognate transcriptional regulator also varied, suggesting that the transcription of these genes independently allows for further fine tuning of each system. Finally, we observe that the activities of both the lasI-lasR and the rhlI-rhlR quorum-sensing systems were dramatically enhanced in the presence of extracts of sputum samples from cystic fibrosis patients.
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Affiliation(s)
- Kangmin Duan
- Faculty of Medicine, Department of Microbiology and Infectious Diseases, Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Canada
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26
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Davies JA, Harrison JJ, Marques LLR, Foglia GR, Stremick CA, Storey DG, Turner RJ, Olson ME, Ceri H. The GacS sensor kinase controls phenotypic reversion of small colony variants isolated from biofilms of Pseudomonas aeruginosa PA14. FEMS Microbiol Ecol 2007; 59:32-46. [PMID: 17233744 DOI: 10.1111/j.1574-6941.2006.00196.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The GacS/GacA two-component regulatory system in pseudomonads regulates genes involved in virulence, secondary metabolism and biofilm formation. Despite these regulatory functions, some Pseudomonas species are prone to spontaneous inactivating mutations in gacA and gacS. A gacS(-) strain of Pseudomonas aeruginosa PA14 was constructed to study the physiological role of this sensor histidine kinase. This loss-of-function mutation was associated with hypermotility, reduced production of acylhomoserine lactones, impaired biofilm maturation, and decreased antimicrobial resistance. Biofilms of the gacS(-) mutant gave rise to phenotypically stable small colony variants (SCVs) with increasing frequency when exposed to silver cations, hydrogen peroxide, human serum, or certain antibiotics (tobramicin, amikacin, azetronam, ceftrioxone, oxacilin, piperacillin or rifampicin). When cultured, the SCV produced thicker biofilms with greater cell density and greater antimicrobial resistance than did the wild-type or parental gacS(-) strains. Similar to other colony morphology variants described in the literature, this SCV was less motile than the wild-type strain and autoaggregated in broth culture. Complementation with gacS in trans restored the ability of the SCV to revert to a normal colony morphotype. These findings indicate that mutation of gacS is associated with the occurrence of stress-resistant SCV cells in P. aeruginosa biofilms and suggests that in some instances GacS may be necessary for reversion of these variants to a wild-type state.
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Affiliation(s)
- James A Davies
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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27
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Affiliation(s)
- Deborah A Hogan
- Department of Microbiology and Immunology, HB7550, Dartmouth Medical School, Hanover NH 03755, USA.
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28
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Auchtung JM, Lee CA, Grossman AD. Modulation of the ComA-dependent quorum response in Bacillus subtilis by multiple Rap proteins and Phr peptides. J Bacteriol 2006; 188:5273-85. [PMID: 16816200 PMCID: PMC1539962 DOI: 10.1128/jb.00300-06] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Bacillus subtilis, extracellular peptide signaling regulates several biological processes. Secreted Phr signaling peptides are imported into the cell and act intracellularly to antagonize the activity of regulators known as Rap proteins. B. subtilis encodes several Rap proteins and Phr peptides, and the processes regulated by many of these Rap proteins and Phr peptides are unknown. We used DNA microarrays to characterize the roles that several rap-phr signaling modules play in regulating gene expression. We found that rapK-phrK regulates the expression of a number of genes activated by the response regulator ComA. ComA activates expression of genes involved in competence development and the production of several secreted products. Two Phr peptides, PhrC and PhrF, were previously known to stimulate the activity of ComA. We assayed the roles that PhrC, PhrF, and PhrK play in regulating gene expression and found that these three peptides stimulate ComA-dependent gene expression to different levels and are all required for full expression of genes activated by ComA. The involvement of multiple Rap proteins and Phr peptides allows multiple physiological cues to be integrated into a regulatory network that modulates the timing and magnitude of the ComA response.
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29
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Cabrera-Valladares N, Richardson AP, Olvera C, Treviño LG, Déziel E, Lépine F, Soberón-Chávez G. Monorhamnolipids and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) production using Escherichia coli as a heterologous host. Appl Microbiol Biotechnol 2006; 73:187-94. [PMID: 16847602 DOI: 10.1007/s00253-006-0468-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 04/11/2006] [Accepted: 04/19/2006] [Indexed: 10/24/2022]
Abstract
Pseudomonas aeruginosa produces the biosurfactants rhamnolipids and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs). In this study, we report the production of one family of rhamnolipids, specifically the monorhamnolipids, and of HAAs in a recombinant Escherichia coli strain expressing P. aeruginosa rhlAB operon. We found that the availability in E. coli of dTDP-L: -rhamnose, a substrate of RhlB, restricts the production of monorhamnolipids in E. coli. We present evidence showing that HAAs and the fatty acid dimer moiety of rhamnolipids are the product of RhlA enzymatic activity. Furthermore, we found that in the recombinant E. coli, these compounds have the same chain length of the fatty acid dimer moiety as those produced by P. aeruginosa. These data suggest that it is RhlAB specificity, and not the hydroxyfatty acid relative abundance in the bacterium, that determines the profile of the fatty acid moiety of rhamnolipids and HAAs. The rhamnolipids level produced in recombinant E. coli expressing rhlAB is lower than the P. aeruginosa level and much higher than those reported by others in E. coli, showing that this metabolic engineering strategy lead to an increased rhamnolipids production in this heterologous host.
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Affiliation(s)
- Natividad Cabrera-Valladares
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Mexico, Mexico
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30
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Abstract
The availability of hundreds of bacterial genome sequences has altered the study of bacterial pathogenesis, affecting both design of experiments and analysis of results. Comparative genomics and genomic tools have been used to identify virulence factors and genes involved in environmental persistence of pathogens. However, a major stumbling block in the genomics revolution has been the large number of genes with unknown function that have been identified in every organism sequenced to date.
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Affiliation(s)
- David M Raskin
- Department of Microbiology & Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
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31
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Smith D, Wang JH, Swatton JE, Davenport P, Price B, Mikkelsen H, Stickland H, Nishikawa K, Gardiol N, Spring DR, Welch M. Variations on a theme: diverse N-acyl homoserine lactone-mediated quorum sensing mechanisms in gram-negative bacteria. Sci Prog 2006; 89:167-211. [PMID: 17338438 PMCID: PMC10368359 DOI: 10.3184/003685006783238335] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Many Gram-negative bacteria employ a mechanism of cell-cell communication known as quorum sensing (QS). The role of QS is to enable the cells in a culture to coordinate their gene expression profile with changes in the population cell density. The best characterized mechanisms of QS employ N-acylated homoserine lactones (AHLs) as signalling molecules. These AHLs are made by enzymes known as LuxI homologs, and accumulate in the culture supernatant at a rate proportional to the increase in cell density. Once the AHL concentration exceeds a certain threshold value, these ligands bind to intracellular receptors known as LuxR homologs. The latter are transcriptional regulators, whose activity alters upon binding the AHL ligand, thereby eliciting a change in gene transcription. Over the last five years, it has become increasingly obvious that this is a rather simplistic view of AHL-dependent QS, and that in fact, there is considerable diversity in the way in which LuxI-R homologs operate. The aim of the current review is to describe these variations on the basic theme, and to show how functional genomics is revolutionizing our understanding of QS-controlled regulons.
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Affiliation(s)
- Debra Smith
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Jin-Hong Wang
- Department of Veterinary Medicine, Madingley Road, Cambridge CB3 OES, UK
| | - Jane E. Swatton
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Peter Davenport
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Bianca Price
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Helga Mikkelsen
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Hannah Stickland
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Kahoko Nishikawa
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
- Department of Traumatology and Critical Care Medicine, National Defense Medical College, 3–2 Namiki Tokorozawa, Saitama, 359–8513 Japan
| | - NoéMie Gardiol
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
| | - David R. Spring
- Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, UK
| | - Martin Welch
- Department of Biochemistry, Building 0, Tennis Court Road, Cambridge CB2 1QW, UK
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32
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Soberón-Chávez G, Lépine F, Déziel E. Production of rhamnolipids by Pseudomonas aeruginosa. Appl Microbiol Biotechnol 2005; 68:718-25. [PMID: 16160828 DOI: 10.1007/s00253-005-0150-3] [Citation(s) in RCA: 292] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 07/15/2005] [Accepted: 08/08/2005] [Indexed: 10/25/2022]
Abstract
Pseudomonas aeruginosa produces glycolipidic surface-active molecules (rhamnolipids) which have potential biotechnological applications. Rhamnolipids are produced by P. aeruginosa in a concerted manner with different virulence-associated traits. Here, we review the rhamnolipids biosynthetic pathway, showing that it has metabolic links with numerous bacterial products such as alginate, lipopolysaccharide, polyhydroxyalkanoates, and 4-hydroxy-2-alkylquinolines (HAQs). We also discuss the factors controlling the production of rhamnolipids and the proposed roles this biosurfactant plays in P. aeruginosa lifestyle.
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Affiliation(s)
- Gloria Soberón-Chávez
- Departamento de Bioprocesos y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Mexico City, Mexico.
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