201
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Luján AM, Maciá MD, Yang L, Molin S, Oliver A, Smania AM. Evolution and adaptation in Pseudomonas aeruginosa biofilms driven by mismatch repair system-deficient mutators. PLoS One 2011; 6:e27842. [PMID: 22114708 PMCID: PMC3219696 DOI: 10.1371/journal.pone.0027842] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 10/26/2011] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas aeruginosa is an important opportunistic pathogen causing chronic airway infections, especially in cystic fibrosis (CF) patients. The majority of the CF patients acquire P. aeruginosa during early childhood, and most of them develop chronic infections resulting in severe lung disease, which are rarely eradicated despite intensive antibiotic therapy. Current knowledge indicates that three major adaptive strategies, biofilm development, phenotypic diversification, and mutator phenotypes [driven by a defective mismatch repair system (MRS)], play important roles in P. aeruginosa chronic infections, but the relationship between these strategies is still poorly understood. We have used the flow-cell biofilm model system to investigate the impact of the mutS associated mutator phenotype on development, dynamics, diversification and adaptation of P. aeruginosa biofilms. Through competition experiments we demonstrate for the first time that P. aeruginosa MRS-deficient mutators had enhanced adaptability over wild-type strains when grown in structured biofilms but not as planktonic cells. This advantage was associated with enhanced micro-colony development and increased rates of phenotypic diversification, evidenced by biofilm architecture features and by a wider range and proportion of morphotypic colony variants, respectively. Additionally, morphotypic variants generated in mutator biofilms showed increased competitiveness, providing further evidence for mutator-driven adaptive evolution in the biofilm mode of growth. This work helps to understand the basis for the specific high proportion and role of mutators in chronic infections, where P. aeruginosa develops in biofilm communities.
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Affiliation(s)
- Adela M. Luján
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María D. Maciá
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto Universitario de Investigación en Ciencias de la Salud (IUNICS), Palma de Mallorca, Spain
| | - Liang Yang
- Department of Systems Biology, Center for Systems Microbiology, Technical University of Denmark, Lyngby, Denmark
| | - Søren Molin
- Department of Systems Biology, Center for Systems Microbiology, Technical University of Denmark, Lyngby, Denmark
| | - Antonio Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto Universitario de Investigación en Ciencias de la Salud (IUNICS), Palma de Mallorca, Spain
| | - Andrea M. Smania
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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202
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Rodríguez-Rojas A, Oliver A, Blázquez J. Intrinsic and environmental mutagenesis drive diversification and persistence of Pseudomonas aeruginosa in chronic lung infections. J Infect Dis 2011; 205:121-7. [PMID: 22080096 DOI: 10.1093/infdis/jir690] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Pseudomonas aeruginosa is a versatile opportunistic pathogen causing a wide variety of hospital-acquired acute infections in immunocompromised patients as well as chronic respiratory infections in patients suffering from cystic fibrosis or other chronic respiratory diseases. Several traits contribute to its ability to colonize and persist in the lungs of chronically infected patients, including development of high resistance to antimicrobials and hypermutability, biofilm growth, and alginate hyperproduction, or a customized pathogenicity, which may include the loss of classical virulence factors and metabolic changes. Here we argue that a combination of both intrinsic and environmental mutagenesis leads to a high number of mutant variants in the population. The conducive environment then triggers a positive feedback loop leading to adaptation and persistence of P. aeruginosa, rendering these chronic infections almost impossible to eradicate.
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Affiliation(s)
- Alexandro Rodríguez-Rojas
- Centro Nacional de Biotecnología (CNB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
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203
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Macià MD, Pérez JL, Molin S, Oliver A. Dynamics of mutator and antibiotic-resistant populations in a pharmacokinetic/pharmacodynamic model of Pseudomonas aeruginosa biofilm treatment. Antimicrob Agents Chemother 2011; 55:5230-7. [PMID: 21859941 PMCID: PMC3195006 DOI: 10.1128/aac.00617-11] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 08/13/2011] [Indexed: 12/17/2022] Open
Abstract
Biofilm growth, antibiotic resistance, and mutator phenotypes are key components of chronic respiratory infections by Pseudomonas aeruginosa in cystic fibrosis patients. We examined the dynamics of mutator and antibiotic-resistant populations in P. aeruginosa flow-cell biofilms, using fluorescently tagged PAO1 and PAOMS (mutator [mutS] derivative) strains. Two-day-old biofilms were treated with ciprofloxacin (CIP) for 4 days (t4) at 2 μg/ml, which correlated with the mutant prevention concentration (MPC) and provided an AUC/MIC ratio of 384 that should predict therapeutic success. Biofilms were monitored by confocal laser scanning microscopy (CLSM), and the numbers of viable cells and resistant mutants (4- and 16-fold MICs) were determined. Despite optimized pharmacokinetic/pharmacodynamic (PK/PD) parameters, CIP treatment did not suppress resistance development in P. aeruginosa biofilms. One-step resistant mutants (MexCD-OprJ or MexEF-OprN overexpression) were selected for both strains, while two-step resistant mutants (additional GyrA or GyrB mutation) were readily selected only from the mutator strain. CLSM analysis of competition experiments revealed that PAOMS, even when inoculated at a 0.01 proportion, took over the whole biofilm after only 2 days of CIP treatment outnumbering PAO1 by 3 log at t4. Our results show that mutational mechanisms play a major role in biofilm antibiotic resistance and that theoretically optimized PK/PD parameters fail to suppress resistance development, suggesting that the increased antibiotic tolerance driven by the special biofilm physiology and architecture may raise the effective MPC, favoring gradual mutational resistance development, especially in mutator strains. Moreover, the amplification of mutator populations under antibiotic treatment by coselection with resistance mutations is for the first time demonstrated in situ for P. aeruginosa biofilms.
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Affiliation(s)
- María D Macià
- Servicio de Microbiología and Unidad de Investigación, Hospital Universitario Son Espases, Palma de Mallorca, Spain.
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204
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Bridier A, Briandet R, Thomas V, Dubois-Brissonnet F. Resistance of bacterial biofilms to disinfectants: a review. BIOFOULING 2011; 27:1017-32. [PMID: 22011093 DOI: 10.1080/08927014.2011.626899] [Citation(s) in RCA: 519] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A biofilm can be defined as a community of microorganisms adhering to a surface and surrounded by a complex matrix of extrapolymeric substances. It is now generally accepted that the biofilm growth mode induces microbial resistance to disinfection that can lead to substantial economic and health concerns. Although the precise origin of such resistance remains unclear, different studies have shown that it is a multifactorial process involving the spatial organization of the biofilm. This review will discuss the mechanisms identified as playing a role in biofilm resistance to disinfectants, as well as novel anti-biofilm strategies that have recently been explored.
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Affiliation(s)
- A Bridier
- AgroParisTech, UMR MICALIS, F-91300 Massy, France
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205
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Eastman JM, Harmon LJ, LA HJ, Joyce P, Forney LJ. The onion model, a simple neutral model for the evolution of diversity in bacterial biofilms. J Evol Biol 2011; 24:2496-504. [PMID: 21929684 DOI: 10.1111/j.1420-9101.2011.02377.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Bacterial biofilms are particularly resistant to a wide variety of antimicrobial compounds. Their persistence in the face of antibiotic therapies causes significant problems in the treatment of infectious diseases. Seldom have evolutionary processes like genetic drift and mutation been invoked to explain how resistance to antibiotics emerges in biofilms, and we lack a simple and tractable model for the genetic and phenotypic diversification that occurs in bacterial biofilms. Here, we introduce the 'onion model', a simple neutral evolutionary model for phenotypic diversification in biofilms. We explore its properties and show that the model produces patterns of diversity that are qualitatively similar to observed patterns of phenotypic diversity in biofilms. We suggest that models like our onion model, which explicitly invoke evolutionary process, are key to understanding biofilm resistance to bactericidal and bacteriostatic agents. Elevated phenotypic variance provides an insurance effect that increases the likelihood that some proportion of the population will be resistant to imposed selective agents and may thus enhance persistence of the biofilm. Accounting for evolutionary change in biofilms will improve our ability to understand and counter diseases that are caused by biofilm persistence.
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Affiliation(s)
- J M Eastman
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA
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206
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Marchal M, Briandet R, Halter D, Koechler S, DuBow MS, Lett MC, Bertin PN. Subinhibitory arsenite concentrations lead to population dispersal in Thiomonas sp. PLoS One 2011; 6:e23181. [PMID: 21876737 PMCID: PMC3158062 DOI: 10.1371/journal.pone.0023181] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 07/07/2011] [Indexed: 11/19/2022] Open
Abstract
Biofilms represent the most common microbial lifestyle, allowing the survival of microbial populations exposed to harsh environmental conditions. Here, we show that the biofilm development of a bacterial species belonging to the Thiomonas genus, frequently found in arsenic polluted sites and playing a key role in arsenic natural remediation, is markedly modified when exposed to subinhibitory doses of this toxic element. Indeed, arsenite [As(III)] exposure led to a considerable impact on biofilm maturation by strongly increasing the extracellular matrix synthesis and by promoting significant cell death and lysis within microcolonies. These events were followed by the development of complex 3D-biofilm structures and subsequently by the dispersal of remobilized cells observed inside the previously formed hollow voids. Our results demonstrate that this biofilm community responds to arsenite stress in a multimodal way, enhancing both survival and dispersal. Addressing this complex bacterial response to As(III) stress, which might be used by other microorganisms under various adverse conditions, may be essential to understand how Thiomonas strains persist in extreme environments.
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Affiliation(s)
- Marie Marchal
- Génétique Moléculaire, Génomique et Microbiologie, UMR7156 CNRS & Université de Strasbourg, Strasbourg, France
| | - Romain Briandet
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Massy, France
| | - David Halter
- Génétique Moléculaire, Génomique et Microbiologie, UMR7156 CNRS & Université de Strasbourg, Strasbourg, France
| | - Sandrine Koechler
- Génétique Moléculaire, Génomique et Microbiologie, UMR7156 CNRS & Université de Strasbourg, Strasbourg, France
| | - Michael S. DuBow
- Université Paris-Sud 11, Institut de Génétique et Microbiologie, CNRS UMR 8621, Orsay, France
| | - Marie-Claire Lett
- Génétique Moléculaire, Génomique et Microbiologie, UMR7156 CNRS & Université de Strasbourg, Strasbourg, France
| | - Philippe N. Bertin
- Génétique Moléculaire, Génomique et Microbiologie, UMR7156 CNRS & Université de Strasbourg, Strasbourg, France
- * E-mail:
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207
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Jefferies JM, Clarke SC, Webb JS, Kraaijeveld AR. Risk of Red Queen dynamics in pneumococcal vaccine strategy. Trends Microbiol 2011; 19:377-81. [DOI: 10.1016/j.tim.2011.06.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 05/27/2011] [Accepted: 06/07/2011] [Indexed: 01/08/2023]
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208
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Competence-dependent endogenous DNA rearrangement and uptake of extracellular DNA give a natural variant of Streptococcus mutans without biofilm formation. J Bacteriol 2011; 193:5147-54. [PMID: 21804005 DOI: 10.1128/jb.05240-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The production of water-insoluble glucan (WIG) enables Streptococcus mutans to survive and persist in the oral niche. WIG is produced from sucrose by glucosyltransferase encoded tandemly by the highly homologous gtfB and gtfC genes. Conversely, a single hybrid gene from the endogenous recombination of gtfB and gtfC is easily generated using RecA, resulting in S. mutans UA159 WIG- (rate of ∼1.0×10(-3)). The pneumococcus recA gene is regulated as a late competence gene. comX gene mutations did not lead to the appearance of WIG- cells. The biofilm collected from the flow cell had more WIG- cells than among the planktonic cells. Among the planktonic cells, WIG- cells appeared after 16 h and increased ∼10-fold after 32 h of cultivation, suggesting an increase in planktonic WIG- cells after longer culture. The strain may be derived from the biofilm environment. In coculture with donor WIG+ and recipient WIG- cells, the recipient cells reverted to WIG+ and acquired an intact gtfBC region from the environment, indicating that the uptake of extracellular DNA resulted in the phenotypic change. Here we demonstrate that endogenous DNA rearrangement and uptake of extracellular DNA generate WIG- cells and that both are induced by the same signal transducer, the com system. Our findings may help in understanding how S. mutans can adapt to the oral environment and may explain the evolution of S. mutans.
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209
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Lambert G, Estévez-Salmeron L, Oh S, Liao D, Emerson BM, Tlsty TD, Austin RH. An analogy between the evolution of drug resistance in bacterial communities and malignant tissues. Nat Rev Cancer 2011; 11:375-82. [PMID: 21508974 PMCID: PMC3488437 DOI: 10.1038/nrc3039] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cancer cells rapidly evolve drug resistance through somatic evolution and, in order to continue growth in the metastatic phase, violate the organism-wide consensus of regulated growth and beneficial communal interactions. We suggest that there is a fundamental mechanistic connection between the rapid evolution of resistance to chemotherapy in cellular communities within malignant tissues and the rapid evolution of antibiotic resistance in bacterial communities. We propose that this evolution is the result of a programmed and collective stress response performed by interacting cells, and that, given this fundamental connection, studying bacterial communities can provide deeper insights into the dynamics of adaptation and the evolution of cells within tumours.
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Affiliation(s)
- Guillaume Lambert
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
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210
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Digestion of extracellular DNA is required for giant colony formation of Staphylococcus aureus. Microb Pathog 2011; 51:142-8. [PMID: 21539906 DOI: 10.1016/j.micpath.2011.04.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 04/08/2011] [Accepted: 04/20/2011] [Indexed: 01/21/2023]
Abstract
Staphylococcus aureus spreads on soft agar surfaces and forms giant colonies. Here, we examined the inhibitory role of extracellular DNA on the colony spreading activity. The double-deletion mutation of nuc1 and nuc2, which encode secretory nucleases, increased extracellular DNA and showed a decreased ability to form giant colonies. The addition of DNase I or micrococcal nuclease to the soft agar restored the ability of the nuc1-nuc2 double mutant to form giant colonies. In addition, the promoter activities of nuc1 and nuc2 in the wild-type strain were elevated in the peripheral region of the giant colony. These findings suggest that the digestion of extracellular DNA by secretory nucleases is required for the colony spreading activity of S. aureus.
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211
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Abstract
Laboratory evolution experiments have led to important findings relating organism adaptation and genomic evolution. However, continuous monitoring of long-term evolution has been lacking for natural systems, limiting our understanding of these processes in situ. Here we characterize the evolutionary dynamics of a lineage of a clinically important opportunistic bacterial pathogen, Pseudomonas aeruginosa, as it adapts to the airways of several individual cystic fibrosis patients over 200,000 bacterial generations, and provide estimates of mutation rates of bacteria in a natural environment. In contrast to predictions based on in vitro evolution experiments, we document limited diversification of the evolving lineage despite a highly structured and complex host environment. Notably, the lineage went through an initial period of rapid adaptation caused by a small number of mutations with pleiotropic effects, followed by a period of genetic drift with limited phenotypic change and a genomic signature of negative selection, suggesting that the evolving lineage has reached a major adaptive peak in the fitness landscape. This contrasts with previous findings of continued positive selection from long-term in vitro evolution experiments. The evolved phenotype of the infecting bacteria further suggests that the opportunistic pathogen has transitioned to become a primary pathogen for cystic fibrosis patients.
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212
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Bacterial SOS response: a food safety perspective. Curr Opin Biotechnol 2011; 22:136-42. [DOI: 10.1016/j.copbio.2010.11.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 11/17/2010] [Accepted: 11/23/2010] [Indexed: 11/19/2022]
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213
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IS5 inserts upstream of the master motility operon flhDC in a quasi-Lamarckian way. ISME JOURNAL 2011; 5:1517-25. [PMID: 21390082 DOI: 10.1038/ismej.2011.27] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mutation rates may be influenced by the environment. Here, we demonstrate that insertion sequence IS5 in Escherichia coli inserts into the upstream region of the flhDC operon in a manner that depends on whether the environment permits motility; this operon encodes the master regulator of cell motility, FlhDC, and the IS5 insertion increases motility. IS5 inserts upstream of flhD(+) when cells are grown on soft-agar plates that permit swimming motility, but does not insert upstream of this locus on hard-agar plates that do not permit swimming motility or in planktonic cultures. Furthermore, there was only one IS5 insertion event on soft-agar plates, indicating insertion of IS5 into flhDC is not due to general elevated IS5 transposition throughout the whole genome. We also show that the highly motile cells with IS5 upstream of flhD(+) have greater biofilm formation, although there is a growth cost due to the energetic burden of the enhanced motility as these highly motile cells have a lower yield in rich medium and reduced growth rate. Functional flagella are required for IS5 insertion upstream of flhD(+) as there was no IS5 insertion upstream of flhD(+) for flhD, flgK and motA mutants, and the mutation is stable. Additionally, the IS5 mutation occurs during biofilm formation, which creates genetic and phenotypic diversity. Hence, the cells appear to 'sense' whether motility is feasible before a sub-population undergoes a mutation to become hypermotile; this sensing appears related to the master transcription regulator, FlhDC.
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214
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Oliver A, Mena A. Bacterial hypermutation in cystic fibrosis, not only for antibiotic resistance. Clin Microbiol Infect 2011; 16:798-808. [PMID: 20880409 DOI: 10.1111/j.1469-0691.2010.03250.x] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hypermutable or mutator microorganisms are those that have an increased spontaneous mutation rate as a result of defects in DNA repair or error avoidance systems. Over the last two decades, several studies have provided strong evidence for a relevant role of mutators in the evolution of natural bacterial populations, particularly in the field of infectious diseases. Among them, chronic respiratory infection with Pseudomonas aeruginosa in cystic fibrosis (CF) patients was the first natural environment to reveal the high prevalence and important role of mutators. A remarkable positive selection of mutators during the course of the chronic infection has been reported, mainly as a result of the emergence of DNA mismatch repair system (mutS, mutL or mutU)-deficient mutants, although strains defective in the GO system (mutM, mutY and mutT) have also been observed. High frequencies of mutators have also been noted among other pathogens in the CF setting, particularly Staphylococcus aureus and Haemophilus influenzae. Enhanced antimicrobial resistance development is the most thoroughly studied consequence of mutators in CF and other chronic infections, although recent studies show that mutators may additionally have important effects on the evolution of virulence, genetic adaptation to the airways of CF patients, persistence of colonization, transmissibility, and perhaps lung function decline. Further prospective clinical studies are nevertheless still needed for an in-depth evaluation of the impact of mutators on disease progression and outcome.
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Affiliation(s)
- A Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud, Palma de Mallorca, Spain.
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215
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The Neisseria gonorrhoeae biofilm matrix contains DNA, and an endogenous nuclease controls its incorporation. Infect Immun 2011; 79:1504-11. [PMID: 21300774 DOI: 10.1128/iai.01162-10] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neisseria gonorrhoeae has been shown to produce biofilms both in experimental flow chambers and in the human host. Our laboratory has shown that extracellular DNA is an essential component of the gonococcal matrix. We have also identified a gene in N. gonorrhoeae, which we designated nuc. This gene has homology with the staphylococcus-secreted thermonuclease. Our laboratory has characterized nuc through phenotypic analysis of a nuc deletion mutant. Biofilms grown with this strain are significantly thicker and of greater biomass than the N. gonorrhoeae 1291 parent strain. Confocal microscopy indicates that the increased size of the mutant biofilms appears to be due to elevated amounts of extracellular DNA in the biofilm matrix. Chromosomal complementation of the nuc mutation restored the wild-type biofilm phenotype. In addition, we have cloned and expressed the Nuc protein in Escherichia coli, and our data indicate that it has the ability to digest multiple forms of DNA and is a thermonuclease. The ability of Nuc to digest DNA also extends to its ability to disrupt established gonococcal biofilms through degradation of the DNA in the biofilm matrix. Our studies indicate that the N. gonorrhoeae biofilm contains DNA and that the Nuc protein appears to play a role in biofilm formation and remodeling.
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216
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Nelson LK, Stanton MM, Elphinstone REA, Helwerda J, Turner RJ, Ceri H. Phenotypic diversification in vivo: Pseudomonas aeruginosa gacS−
strains generate small colony variants in vivo that are distinct from in vitro variants. Microbiology (Reading) 2010; 156:3699-3709. [DOI: 10.1099/mic.0.040824-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Pseudomonas aeruginosa has long been known to produce phenotypic variants during chronic mucosal surface infections. These variants are thought to be generated to ensure bacterial survival against the diverse challenges in the mucosal environment. Studies have begun to elucidate the mechanisms by which these variants emerge in vitro; however, too little information exists on phenotypic variation in vivo to draw any links between variants generated in vitro and in vivo. Consequently, in this study, the P. aeruginosa gacS gene, which has previously been linked to the generation of small colony variants (SCVs) in vitro, was studied in an in vivo mucosal surface infection model. More specifically, the rat prostate served as a model mucosal surface to test for the appearance of SCVs in vivo following infections with P. aeruginosa gacS−
strains. As in in vitro studies, deletion of the gacS gene led to SCV production in vivo. The appearance of these in vivo SCVs was important for the sustainability of a chronic infection. In the subset of rats in which P. aeruginosa
gacS−
did not convert to SCVs, clearance of the bacteria took place and healing of the tissue ensued. When comparing the SCVs that arose at the mucosal surface (MS-SCVs) with in vitro SCVs (IV-SCVs) from the same gacS−
parent, some differences between the phenotypic variants were observed. Whereas both MS-SCVs and IV-SCVs formed dense biofilms, MS-SCVs exhibited a less diverse resistance profile to antimicrobial agents than IV-SCVs. Additionally, MS-SCVs were better suited to initiate an infection in the rat model than IV-SCVs. Together, these observations suggest that phenotypic variation in vivo can be important for maintenance of infection, and that in vivo variants may differ from in vitro variants generated from the same genetic parent.
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Affiliation(s)
- Lisa K. Nelson
- Biofilm Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
| | - M. Mark Stanton
- Biofilm Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
| | - Robyn E. A. Elphinstone
- Biofilm Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
| | - Janessa Helwerda
- Biofilm Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
| | - Raymond J. Turner
- Biofilm Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
| | - Howard Ceri
- Biofilm Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
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217
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Importance of SigB for Listeria monocytogenes static and continuous-flow biofilm formation and disinfectant resistance. Appl Environ Microbiol 2010; 76:7854-60. [PMID: 20889779 DOI: 10.1128/aem.01519-10] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Listeria monocytogenes is a food-borne pathogen that is able to form biofilms in food processing facilities. Biofilms are generally more resistant to antimicrobial agents, making it difficult to eradicate them during cleanup procedures. So far, little is known about the function of stress resistance mechanisms in biofilm formation and their resistance to disinfectants. In this study, we investigated the role of sigB, which encodes a major transcriptional regulator of stress response genes, in L. monocytogenes static and continuous-flow biofilm formation and its function in the resistance of biofilm cells to the disinfectants benzalkonium chloride and peracetic acid. Quantitative real-time PCR and promoter reporter studies showed that sigB is activated in static and continuous-flow biofilms. Biofilm formation studies using an in-frame sigB deletion mutant and complementation mutant showed that the presence of SigB is required to obtain wild-type levels of both static and continuous-flow biofilms. Finally, disinfection treatments of planktonically grown cells and cells dispersed from static and continuous-flow biofilms showed that SigB is involved in the resistance of both planktonic cells and biofilms to the disinfectants benzalkonium chloride and peracetic acid.
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218
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Abstract
Lung infections caused by the opportunistic pathogen Pseudomonas aeruginosa can present as a spectrum of clinical entities from a rapidly fatal pneumonia in a neutropenic patient to a multi-decade bronchitis in patients with cystic fibrosis. P. aeruginosa is ubiquitous in our environment, and one of the most versatile pathogens studied, capable of infecting a number of diverse life forms and surviving harsh environmental factors. It is also able to quickly adapt to new environments, including the lung, where it orchestrates virulence factors to acquire necessary nutrients, and if necessary, turn them off to prevent immune recognition. Despite these capabilities, P. aeruginosa rarely infects healthy human lungs. This is secondary to a highly evolved host defence mechanism that efficiently removes inhaled or aspirated pseudomonads. Many arms of the respiratory host defence have been elucidated using P. aeruginosa as a model pathogen. Human infections with P. aeruginosa have demonstrated the importance of the mechanical barrier functions including mucus clearance, and the innate immune system, including the critical role of the neutrophilic response. As more models of persistent or biofilm P. aeruginosa infections are developed, the role of the adaptive immune response will likely become more evident. Understanding the pathogenesis of P. aeruginosa, and the respiratory host defence response to it has, and will continue to, lead to novel therapeutic strategies to help patients.
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Affiliation(s)
- Bryan J Williams
- Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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219
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Separate DNA Pol II- and Pol IV-dependent pathways of stress-induced mutation during double-strand-break repair in Escherichia coli are controlled by RpoS. J Bacteriol 2010; 192:4694-700. [PMID: 20639336 DOI: 10.1128/jb.00570-10] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous work showed that about 85% of stress-induced mutations associated with DNA double-strand break repair in carbon-starved Escherichia coli result from error-prone DNA polymerase IV (Pol IV) (DinB) and that the mutagenesis is controlled by the RpoS stress response, which upregulates dinB. We report that the remaining mutagenesis requires high-fidelity Pol II, and that this component also requires RpoS. The results identify a second DNA polymerase contributing to stress-induced mutagenesis and show that RpoS promotes mutagenesis by more than the simple upregulation of dinB.
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220
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Pham TK, Roy S, Noirel J, Douglas I, Wright PC, Stafford GP. A quantitative proteomic analysis of biofilm adaptation by the periodontal pathogen Tannerella forsythia. Proteomics 2010; 10:3130-41. [DOI: 10.1002/pmic.200900448] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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221
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Rao D, Skovhus T, Tujula N, Holmström C, Dahllöf I, Webb JS, Kjelleberg S. Ability of Pseudoalteromonas tunicata to colonize natural biofilms and its effect on microbial community structure. FEMS Microbiol Ecol 2010; 73:450-7. [DOI: 10.1111/j.1574-6941.2010.00917.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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222
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Kivisaar M. Mechanisms of stationary-phase mutagenesis in bacteria: mutational processes in pseudomonads. FEMS Microbiol Lett 2010; 312:1-14. [DOI: 10.1111/j.1574-6968.2010.02027.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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223
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Gibson JL, Lombardo MJ, Thornton PC, Hu KH, Galhardo RS, Beadle B, Habib A, Magner DB, Frost LS, Herman C, Hastings PJ, Rosenberg SM. The sigma(E) stress response is required for stress-induced mutation and amplification in Escherichia coli. Mol Microbiol 2010; 77:415-30. [PMID: 20497332 PMCID: PMC2909356 DOI: 10.1111/j.1365-2958.2010.07213.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Pathways of mutagenesis are induced in microbes under adverse conditions controlled by stress responses. Control of mutagenesis by stress responses may accelerate evolution specifically when cells are maladapted to their environments, i.e. are stressed. Stress-induced mutagenesis in the Escherichia coli Lac assay occurs either by ‘point’ mutation or gene amplification. Point mutagenesis is associated with DNA double-strand-break (DSB) repair and requires DinB error-prone DNA polymerase and the SOS DNA-damage- and RpoS general-stress responses. We report that the RpoE envelope-protein-stress response is also required. In a screen for mutagenesis-defective mutants, we isolated a transposon insertion in the rpoE P2 promoter. The insertion prevents rpoE induction during stress, but leaves constitutive expression intact, and allows cell viability. rpoE insertion and suppressed null mutants display reduced point mutagenesis and maintenance of amplified DNA. Furthermore, σE acts independently of stress responses previously implicated: SOS/DinB and RpoS, and of σ32, which was postulated to affect mutagenesis. I-SceI-induced DSBs alleviated much of the rpoE phenotype, implying that σE promoted DSB formation. Thus, a third stress response and stress input regulate DSB-repair-associated stress-induced mutagenesis. This provides the first report of mutagenesis promoted by σE, and implies that extracytoplasmic stressors may affect genome integrity and, potentially, the ability to evolve.
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Affiliation(s)
- Janet L Gibson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030-3411, USA
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224
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Workentine ML, Harrison JJ, Weljie AM, Tran VA, Stenroos PU, Tremaroli V, Vogel HJ, Ceri H, Turner RJ. Phenotypic and metabolic profiling of colony morphology variants evolved fromPseudomonas fluorescensbiofilms. Environ Microbiol 2010; 12:1565-77. [DOI: 10.1111/j.1462-2920.2010.02185.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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225
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Høiby N, Bjarnsholt T, Givskov M, Molin S, Ciofu O. Antibiotic resistance of bacterial biofilms. Int J Antimicrob Agents 2010; 35:322-32. [PMID: 20149602 DOI: 10.1016/j.ijantimicag.2009.12.011] [Citation(s) in RCA: 1939] [Impact Index Per Article: 138.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2009] [Accepted: 12/15/2009] [Indexed: 02/06/2023]
Abstract
A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and DNA. Bacterial biofilms cause chronic infections because they show increased tolerance to antibiotics and disinfectant chemicals as well as resisting phagocytosis and other components of the body's defence system. The persistence of, for example, staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infection in cystic fibrosis patients is caused by biofilm-growing mucoid strains. Characteristically, gradients of nutrients and oxygen exist from the top to the bottom of biofilms and these gradients are associated with decreased bacterial metabolic activity and increased doubling times of the bacterial cells; it is these more or less dormant cells that are responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations as well as with quorum-sensing-regulated mechanisms. Conventional resistance mechanisms such as chromosomal beta-lactamase, upregulated efflux pumps and mutations in antibiotic target molecules in bacteria also contribute to the survival of biofilms. Biofilms can be prevented by early aggressive antibiotic prophylaxis or therapy and they can be treated by chronic suppressive therapy. A promising strategy may be the use of enzymes that can dissolve the biofilm matrix (e.g. DNase and alginate lyase) as well as quorum-sensing inhibitors that increase biofilm susceptibility to antibiotics.
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Affiliation(s)
- Niels Høiby
- Department of Clinical Microbiology 9301, Juliane Mariesvej 22, Rigshospitalet, 2100 Copenhagen, Denmark.
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226
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Shin JH, Lee HW, Kim SM, Kim J. Proteomic analysis of Acinetobacter baumannii in biofilm and planktonic growth mode. J Microbiol 2010; 47:728-35. [PMID: 20127467 DOI: 10.1007/s12275-009-0158-y] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Accepted: 07/08/2009] [Indexed: 01/12/2023]
Abstract
Recently, multidrug-resistant clinical isolates of Acinetobacter baumannii have been found to have a high capacity to form biofilm. It is well known that bacterial cells within biofilms are highly resistant to antibiotics, UV light, acid exposure, dehydration, and phagocytosis in comparison to their planktonic counterparts, which suggests that the cells in a biofilm have altered metabolic activity. To determine which proteins are up-regulated in A. baumannii biofilm cells, we performed a proteomic analysis. A clinical isolate of A. baumannii 1656-2, which was characterized to have a high biofilm forming ability, was cultivated under biofilm and planktonic conditions. Outer membrane enriched A. baumannii 1656-2 proteins were separated by two-dimensional (2-D) gel electrophoresis and the differentially expressed proteins were identified by MALDI-TOF mass spectrometry. The proteins up-regulated or expressed only in biofilm cells of A. baumannii are categorized as follows: (i) proteins processing environmental information such as the outer membrane receptor protein involved in mostly Fe transport, a sensor histidine kinase/response regulator, and diguanylate cyclase (PAS-GGEDF-EAL domain); (ii) proteins involved in metabolism such as NAD-linked malate dehydrogenase, nucleoside-diphosphate sugar epimerase, putative GalE, ProFAR isomerase, and N-acetylmuramoyl-L: -alanine amidase; (iii) bacterial antibiotic resistance related proteins; and (iv) proteins related to gene repair such as exodeoxyribonuclease III and GidA. This proteomic analysis provides a fundamental platform for further studies to reveal the role of biofilm in the persistence and tolerance of A. baumannii.
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Affiliation(s)
- Ji-Hyun Shin
- Department of Microbiology, Kyungpook National University, School of Medicine, Daegu 700-422, Republic of Korea
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227
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Müsken M, Di Fiore S, Dötsch A, Fischer R, Häussler S. Genetic determinants of Pseudomonas aeruginosa biofilm establishment. Microbiology (Reading) 2010; 156:431-441. [DOI: 10.1099/mic.0.033290-0] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The establishment of bacterial biofilms on surfaces is a complex process that requires various factors for each consecutive developmental step. Here we report the screening of the comprehensive Harvard Pseudomonas aeruginosa PA14 mutant library for mutants exhibiting an altered biofilm phenotype. We analysed the capability of all mutants to form biofilms at the bottom of a 96-well plate by the use of an automated confocal laser-scanning microscope and found 394 and 285 genetic determinants of reduced and enhanced biofilm production, respectively. Overall, 67 % of the identified mutants were affected within genes encoding hypothetical proteins, indicating that novel developmental pathways are likely to be dissected in the future. Nevertheless, a common theme that emerged from the analysis of the genes with a predicted function is that the establishment of a biofilm requires regulatory components that are involved in survival under microaerophilic growth conditions, arginine metabolism, alkyl-quinolone signalling, pH homeostasis and the DNA repair system.
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Affiliation(s)
- Mathias Müsken
- Chronic Pseudomonas Infection Research Group, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
| | - Stefano Di Fiore
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeck Str. 6, D-52704 Aachen, Germany
- Institute for Molecular Biotechnology, RWTH Aachen University, Worringerweg 1, D-52704 Aachen, Germany
| | - Andreas Dötsch
- Chronic Pseudomonas Infection Research Group, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
| | - Rainer Fischer
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeck Str. 6, D-52704 Aachen, Germany
| | - Susanne Häussler
- Twincore, Center for Experimental and Clinical Infection Research, a joint venture of the Helmholtz Center for Infection Research and the Medical School Hannover, Feodor Lynen Strasse 7, D-30265 Hannover, Germany
- Chronic Pseudomonas Infection Research Group, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
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228
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Narisawa N. Development, Characterization and Ecological Implications of a Smooth Colony Variant of Biofilm-forming Cariogenic Streptococcus mutans. J Oral Biosci 2010. [DOI: 10.1016/s1349-0079(10)80028-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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229
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Fothergill JL, Mowat E, Ledson MJ, Walshaw MJ, Winstanley C. Fluctuations in phenotypes and genotypes within populations of Pseudomonas aeruginosa in the cystic fibrosis lung during pulmonary exacerbations. J Med Microbiol 2009; 59:472-481. [PMID: 20019149 DOI: 10.1099/jmm.0.015875-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chronic respiratory infection by Pseudomonas aeruginosa contributes significantly to the morbidity and mortality associated with cystic fibrosis (CF). Using a series of phenotypic and genotypic tests on collections of 40 isolates per sputum sample, we analysed fluctuations within sputum populations of the P. aeruginosa Liverpool epidemic strain (LES) during pulmonary exacerbations. For each of three patients, three sequential sputum samples were analysed: (1) on presentation with exacerbation at the Regional Adult Cystic Fibrosis Unit, Liverpool; (2) a few days into intravenous antibiotic treatment; (3) when the patient had recovered. Fluctuations were observed in morphotype distribution, the production of virulence-associated quorum-sensing-dependent exoproducts (the phenazine compound pyocyanin and the elastase LasA), antibiotic susceptibility profiles and levels of auxotrophy. PCR assays were used to screen isolates for the presence of novel regions of the LES genome (islands and prophages) and to detect free phages. In one patient there was an increase in the prevalence of the LESGI-5 genomic island during the sampling period from 10 to 97.5 % carriage. LES phages 2-4 were detected in either the majority or all sputum samples tested, indicating widespread phage activity during the sampling period. The results of this study are indicative that significant fluctuations occur within P. aeruginosa populations during short periods of pulmonary exacerbation and intravenous antibiotic therapy.
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Affiliation(s)
- Joanne L Fothergill
- Division of Medical Microbiology, School of Infectionand Host Defence, University of Liverpool, Liverpool L69 3GA, UK.,Biomedical Research Centre, Royal Liverpool UniversityHospital, Liverpool L69 3GA, UK
| | - Eilidh Mowat
- Division of Medical Microbiology, School of Infectionand Host Defence, University of Liverpool, Liverpool L69 3GA, UK
| | - Martin J Ledson
- Regional Adult Cystic Fibrosis Unit, Liverpool Heartand Chest Hospital, Liverpool L14 3PE, UK
| | - Martin J Walshaw
- Regional Adult Cystic Fibrosis Unit, Liverpool Heartand Chest Hospital, Liverpool L14 3PE, UK
| | - Craig Winstanley
- Division of Medical Microbiology, School of Infectionand Host Defence, University of Liverpool, Liverpool L69 3GA, UK.,Biomedical Research Centre, Royal Liverpool UniversityHospital, Liverpool L69 3GA, UK
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230
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Evolution of diversity in spatially structured Escherichia coli populations. Appl Environ Microbiol 2009; 75:6047-54. [PMID: 19648364 DOI: 10.1128/aem.00063-09] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The stochastic Ricker population model was used to investigate the generation and maintenance of genetic diversity in a bacterial population grown in a spatially structured environment. In particular, we showed that Escherichia coli undergoes dramatic genetic diversification when grown as a biofilm. Using a novel biofilm entrapment method, we retrieved 64 clones from each of six different depths of a mature biofilm, and after subculturing for approximately 30 generations, we measured their growth kinetics in three different media. We fit a stochastic Ricker population growth model to the recorded growth curves. The growth kinetics of clonal lineages descendant from cells sampled at different biofilm depths varied as a function of both the depth in the biofilm and the growth medium used. We concluded that differences in the growth dynamics of clones were heritable and arose during adaptive evolution under local conditions in a spatially heterogeneous environment. We postulate that under nutrient-limited conditions, selective sweeps would be protracted and would be insufficient to purge less-fit variants, a phenomenon that would allow the coexistence of genetically distinct clones. These findings contribute to the current understanding of biofilm ecology and complement current hypotheses for the maintenance and generation of microbial diversity in spatially structured environments.
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231
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Role of mutation in Pseudomonas aeruginosa biofilm development. PLoS One 2009; 4:e6289. [PMID: 19606212 PMCID: PMC2705801 DOI: 10.1371/journal.pone.0006289] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 06/10/2009] [Indexed: 01/09/2023] Open
Abstract
The survival of bacteria in nature is greatly enhanced by their ability to grow within surface-associated communities called biofilms. Commonly, biofilms generate proliferations of bacterial cells, called microcolonies, which are highly recalcitrant, 3-dimensional foci of bacterial growth. Microcolony growth is initiated by only a subpopulation of bacteria within biofilms, but processes responsible for this differentiation remain poorly understood. Under conditions of crowding and intense competition between bacteria within biofilms, microevolutionary processes such as mutation selection may be important for growth; however their influence on microcolony-based biofilm growth and architecture have not previously been explored. To study mutation in-situ within biofilms, we transformed Pseudomonas aeruginosa cells with a green fluorescent protein gene containing a +1 frameshift mutation. Transformed P. aeruginosa cells were non-fluorescent until a mutation causing reversion to the wildtype sequence occurs. Fluorescence-inducing mutations were observed in microcolony structures, but not in other biofilm cells, or in planktonic cultures of P. aeruginosa cells. Thus microcolonies may represent important foci for mutation and evolution within biofilms. We calculated that microcolony-specific increases in mutation frequency were at least 100-fold compared with planktonically grown cultures. We also observed that mutator phenotypes can enhance microcolony-based growth of P. aeruginosa cells. For P. aeruginosa strains defective in DNA fidelity and error repair, we found that microcolony initiation and growth was enhanced with increased mutation frequency of the organism. We suggest that microcolony-based growth can involve mutation and subsequent selection of mutants better adapted to grow on surfaces within crowded-cell environments. This model for biofilm growth is analogous to mutation selection that occurs during neoplastic progression and tumor development, and may help to explain why structural and genetic heterogeneity are characteristic features of bacterial biofilm populations.
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232
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Resta SC. Effects of probiotics and commensals on intestinal epithelial physiology: implications for nutrient handling. J Physiol 2009; 587:4169-74. [PMID: 19596893 DOI: 10.1113/jphysiol.2009.176370] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Eukaryotes and prokaryotes have developed mutually beneficial relationships over millennia of evolutionary adaptation. Bacteria in our gut rely on our diet and the protected environment of our bodies just as our health depends on byproducts of microbial metabolism. Microorganisms of the gut microbiota ferment carbohydrates into short-chain fatty acids, convert dietary and endogenous nitrogenous compounds into ammonia and microbial protein, and synthesize and activate B vitamins and vitamin K. The benefit from their activity is multiplex and translates into increased energy for the gut epithelial cells, balanced absorption of salt and water, nitrogen recycling, breakdown of complex lipids and cholesterol, and detoxification of waste compounds.
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Affiliation(s)
- Silvia C Resta
- Department of Medicine, UCSD, School of Medicine, 9500 Gilman Drive, UC 303, MC0063, La Jolla, CA 92093-0063, USA.
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233
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Rajkovic A, Smigic N, Uyttendaele M, Medic H, de Zutter L, Devlieghere F. Resistance of Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter jejuni after exposure to repetitive cycles of mild bactericidal treatments. Food Microbiol 2009; 26:889-95. [PMID: 19835777 DOI: 10.1016/j.fm.2009.06.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 05/26/2009] [Accepted: 06/05/2009] [Indexed: 11/17/2022]
Abstract
While maintaining nutritional and sensorial attributes of fresh foods mild processing technologies generally deliver microbiologically perishable food products. Currently little information exists on possible increase in the resistance of pathogens after repetitive exposure to mild (sub-lethal) treatments. Multiple strain-cocktails of Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter jejuni were exposed to 20 consecutive cycles of sub-lethal inactivation by three different techniques. Used techniques comprised inactivation with lactic acid (LA), chlorine dioxide (ClO(2)) and intense light pulses (ILP). Results showed that the selection of resistant cells was both species and technique dependent. While repetitive cycles of ClO(2) treatment did not result in increased resistance, repetitive inactivation with LA yielded L. monocytogenes culture of higher resistance in comparison to the parental culture. The increased resistance, expressed as decreased level of reduction in bacterial counts in subsequent inactivation cycles, was also observed with ILP for both L. monocytogenes and E. coli O157:H7 strains. Visual trend observations were confirmed through statistical linear regression analysis. No such effects were noted for C. jejuni which became undetectable after first 2-5 cycles. Current findings indicate the ability of foodborne pathogens to adapt to mild bactericidal treatments creating new challenges in risk assessment and more specifically in hazard analysis.
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Affiliation(s)
- Andreja Rajkovic
- Laboratory of Food Microbiology and Food Preservation, Department of Food Safety and Food Quality, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Gent, Belgium
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234
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Pseudomonas aeruginosa rugose small-colony variants have adaptations that likely promote persistence in the cystic fibrosis lung. J Bacteriol 2009; 191:3492-503. [PMID: 19329647 DOI: 10.1128/jb.00119-09] [Citation(s) in RCA: 274] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Pseudomonas aeruginosa is recognized for its ability to colonize diverse habitats, ranging from soil to immunocompromised people. The formation of surface-associated communities called biofilms is one factor thought to enhance colonization and persistence in these diverse environments. Another factor is the ability of P. aeruginosa to diversify genetically, generating phenotypically distinct subpopulations. One manifestation of diversification is the appearance of colony morphology variants on solid medium. Both laboratory biofilm growth and chronic cystic fibrosis (CF) airway infections produce rugose small-colony variants (RSCVs) characterized by wrinkled, small colonies and an elevated capacity to form biofilms. Previous reports vary on the characteristics attributable to RSCVs. Here we report a detailed comparison of clonally related wild-type and RSCV strains isolated from both CF sputum and laboratory biofilm cultures. The clinical RSCV had many characteristics in common with biofilm RSCVs. Transcriptional profiling and Biolog phenotypic analysis revealed that RSCVs display increased expression of the pel and psl polysaccharide gene clusters, decreased expression of motility functions, and a defect in growth on some amino acid and tricarboxylic acid cycle intermediates as sole carbon sources. RSCVs also elicited a reduced chemokine response from polarized airway epithelium cells compared to wild-type strains. A common feature of all RSCVs analyzed in this study is increased levels of the intracellular signaling molecule cyclic di-GMP (c-di-GMP). To assess the global transcriptional effects of elevated c-di-GMP levels, we engineered an RSCV strain that had elevated c-di-GMP levels but did not autoaggregate. Our results showed that about 50 genes are differentially expressed in response to elevated intracellular c-di-GMP levels. Among these genes are the pel and psl genes, which are upregulated, and flagellum and pilus genes, which are downregulated. RSCV traits such as increased exopolysaccharide production leading to antibiotic tolerance, altered metabolism, and reduced immunogenicity may contribute to increased persistence in biofilms and in the airways of CF lungs.
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