501
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Overhage J, Campisano A, Bains M, Torfs ECW, Rehm BHA, Hancock REW. Human host defense peptide LL-37 prevents bacterial biofilm formation. Infect Immun 2008; 76:4176-82. [PMID: 18591225 PMCID: PMC2519444 DOI: 10.1128/iai.00318-08] [Citation(s) in RCA: 464] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 04/22/2008] [Accepted: 06/25/2008] [Indexed: 01/28/2023] Open
Abstract
The ability to form biofilms is a critical factor in chronic infections by Pseudomonas aeruginosa and has made this bacterium a model organism with respect to biofilm formation. This study describes a new, previously unrecognized role for the human cationic host defense peptide LL-37. In addition to its key role in modulating the innate immune response and weak antimicrobial activity, LL-37 potently inhibited the formation of bacterial biofilms in vitro. This occurred at the very low and physiologically meaningful concentration of 0.5 microg/ml, far below that required to kill or inhibit growth (MIC = 64 microg/ml). LL-37 also affected existing, pregrown P. aeruginosa biofilms. Similar results were obtained using the bovine neutrophil peptide indolicidin, but no inhibitory effect on biofilm formation was detected using subinhibitory concentrations of the mouse peptide CRAMP, which shares 67% identity with LL-37, polymyxin B, or the bovine bactenecin homolog Bac2A. Using microarrays and follow-up studies, we were able to demonstrate that LL-37 affected biofilm formation by decreasing the attachment of bacterial cells, stimulating twitching motility, and influencing two major quorum sensing systems (Las and Rhl), leading to the downregulation of genes essential for biofilm development.
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Affiliation(s)
- Joerg Overhage
- Centre for Microbial Diseases & Immunity Research, University of British Columbia, Vancouver, British Columbia, Canada
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502
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Modulation of secreted virulence factor genes by subinhibitory concentrations of antibiotics in Pseudomonas aeruginosa. J Microbiol 2008; 46:441-7. [PMID: 18758736 DOI: 10.1007/s12275-008-0054-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 06/20/2008] [Indexed: 10/21/2022]
Abstract
Recent studies have shown that subinhibitory antibiotics play important roles in regulating bacterial genes including virulence factor genes. In this study, the expression of 13 secreted virulence related gene clusters of Pseudomonas aeruginosa, an important opportunistic pathogen, was examined in the presence of subinhibitory concentrations of 4 antibiotics: vancomycin, tetracycline, ampicillin and azithromycin. Activation of gene expression was observed with phzAl, rhlAB, phzA2, lasB, exoY, and exoS. Subinhibitory concentrations of vancomycin resulted in more than 10-fold increase of rhlAB and phzA2 transcription. Both rhamnolipid production and pyocyanin production were significantly elevated, correlating phenotypes with the increased transcription. P. aeruginosa swarming and swimming motility also increased. Similar results were observed with subinhibitory tetracycline, azithromycin and ampicillin. These results indicate that the antibiotics at low concentrations can up-regulate virulence factors and therefore influence bacterial pathogenesis.
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503
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The YebC family protein PA0964 negatively regulates the Pseudomonas aeruginosa quinolone signal system and pyocyanin production. J Bacteriol 2008; 190:6217-27. [PMID: 18641136 DOI: 10.1128/jb.00428-08] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial pathogenicity is often manifested by the expression of various cell-associated and secreted virulence factors, such as exoenzymes, protease, and toxins. In Pseudomonas aeruginosa, the expression of virulence genes is coordinately controlled by the global regulatory quorum-sensing systems, which includes the las and rhl systems as well as the Pseudomonas quinolone signal (PQS) system. Phenazine compounds are among the virulence factors under the control of both the rhl and PQS systems. In this study, regulation of the phzA1B1C1D1E1 (phzA1) operon, which is involved in phenazine synthesis, was investigated. In an initial study of inducing conditions, we observed that phzA1 was induced by subinhibitory concentrations of tetracycline. Screening of 13,000 mutants revealed 32 genes that altered phzA1 expression in the presence of subinhibitory tetracycline concentrations. Among them, the gene PA0964, designated pmpR (pqsR-mediated PQS regulator), has been identified as a novel regulator of the PQS system. It belongs to a large group of widespread conserved hypothetical proteins with unknown function, the YebC protein family (Pfam family DUF28). It negatively regulates the quorum-sensing response regulator pqsR of the PQS system by binding at its promoter region. Alongside phzA1 expression and phenazine and pyocyanin production, a set of virulence factors genes controlled by both rhl and the PQS were shown to be modulated by PmpR. Swarming motility and biofilm formation were also significantly affected. The results added another layer of regulation in the rather complex quorum-sensing systems in P. aeruginosa and demonstrated a clear functional clue for the YebC family proteins.
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504
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Inoue T, Shingaki R, Fukui K. Inhibition of swarming motility of Pseudomonas aeruginosa by branched-chain fatty acids. FEMS Microbiol Lett 2008; 281:81-6. [PMID: 18318842 DOI: 10.1111/j.1574-6968.2008.01089.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Pseudomonas aeruginosa is capable of moving by swimming, swarming, and twitching motilities. In this study, we investigated the effects of fatty acids on Pseudomonas aeruginosa PAO1 motilities. A branched-chain fatty acid (BCFA)--12-methyltetradecanoic acid (anteiso-C15:0)--has slightly repressed flagella-driven swimming motility and completely inhibited a more complex type of surface motility, i.e. swarming, at a concentration of 10 microg mL(-1). In contrast, anteiso-C15:0 exhibited no effect on pili-mediated twitching motility. Other BCFAs and unsaturated fatty acids tested in this study showed similar inhibitory effects on swarming motility, although the level of inhibition differed between these fatty acids. These fatty acids caused no significant growth inhibition in liquid cultures. Straight-chain saturated fatty acids such as palmitic acid were less effective in swarming inhibition. The wetness of the PAO1 colony was significantly reduced by the addition of anteiso-C15:0; however, the production of rhamnolipids as a surface-active agent was not affected by the fatty acid. In addition to motility repression, anteiso-C15:0 caused 31% repression of biofilm formation by PAO1, suggesting that BCFA could affect the multiple cellular activities of Pseudomonas aeruginosa.
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Affiliation(s)
- Tetsuyoshi Inoue
- Department of Oral Microbiology, Okayama University of Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Shikata-cho, Okayama, Japan.
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505
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Barken KB, Pamp SJ, Yang L, Gjermansen M, Bertrand JJ, Klausen M, Givskov M, Whitchurch CB, Engel JN, Tolker-Nielsen T. Roles of type IV pili, flagellum-mediated motility and extracellular DNA in the formation of mature multicellular structures in Pseudomonas aeruginosa biofilms. Environ Microbiol 2008; 10:2331-43. [PMID: 18485000 DOI: 10.1111/j.1462-2920.2008.01658.x] [Citation(s) in RCA: 277] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
When grown as a biofilm in laboratory flow chambers Pseudomonas aeruginosa can develop mushroom-shaped multicellular structures consisting of distinct subpopulations in the cap and stalk portions. We have previously presented evidence that formation of the cap portion of the mushroom-shaped structures in P. aeruginosa biofilms occurs via bacterial migration and depends on type IV pili (Mol Microbiol 50: 61-68). In the present study we examine additional factors involved in the formation of this multicellular substructure. While pilA mutants, lacking type IV pili, are deficient in mushroom cap formation, pilH and chpA mutants, which are inactivated in the type IV pili-linked chemosensory system, showed only minor defects in cap formation. On the contrary, fliM mutants, which are non-flagellated, and cheY mutants, which are inactivated in the flagellum-linked chemotaxis system, were largely deficient in cap formation. Experiments involving DNase treatment of developing biofilms provided evidence that extracellular DNA plays a role in cap formation. Moreover, mutants that are deficient in quorum sensing-controlled DNA release formed microcolonies upon which wild-type bacteria could not form caps. These results constitute evidence that type IV pili, flagellum-mediated motility and quorum sensing-controlled DNA release are involved in the formation of mature multicellular structures in P. aeruginosa biofilms.
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Affiliation(s)
- Kim B Barken
- Centre for Biomedical Microbiology, Technical University of Denmark, DK-2800, Lyngby, Denmark
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506
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Matilla MA, Ramos JL, Duque E, de Dios Alché J, Espinosa-Urgel M, Ramos-González MI. Temperature and pyoverdine-mediated iron acquisition control surface motility of Pseudomonas putida. Environ Microbiol 2008; 9:1842-50. [PMID: 17564617 DOI: 10.1111/j.1462-2920.2007.01286.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pseudomonas putida KT2440 is unable to swarm at its common temperature of growth in the laboratory (30 degrees C) but exhibits surface motility similar to swarming patterns in other Pseudomonas between 18 degrees C and 28 degrees C. These motile cells show differentiation, consisting on elongation and the presence of surface appendages. Analysis of a collection of mutants to define the molecular determinants of this type of surface movement in KT2440 shows that while type IV pili and lipopolysaccharide O-antigen are requisites flagella are not. Although surface motility of flagellar mutants was macroscopically undistinguishable from that of the wild type, microscopy analysis revealed that these mutants move using a distinct mechanism to that of the wild-type strain. Mutants either in the siderophore pyoverdine (ppsD) or in the FpvA siderophore receptor were also unable to spread on surfaces. Motility in the ppsD strain was totally restored with pyoverdine and partially with the wild-type ppsD allele. Phenotype of the fpvA strain was not complemented by this siderophore. We discuss that iron influences surface motility and that it can be an environmental cue for swarming-like movement in P. putida. This study constitutes the first report assigning an important role to pyoverdine iron acquisition in en masse bacterial surface movement.
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Affiliation(s)
- Miguel A Matilla
- Department of Environmental Protection, Estación Experimental del Zaidin, CSIC, Profesor Albareda, 1 Granada 18008, Spain
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507
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Chandra H, Khandelwal P, Khattri A, Banerjee N. Type 1 fimbriae of insecticidal bacterium Xenorhabdus nematophila is necessary for growth and colonization of its symbiotic host nematode Steinernema carpocapsiae. Environ Microbiol 2008; 10:1285-95. [PMID: 18279345 DOI: 10.1111/j.1462-2920.2007.01542.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Xenorhabdus nematophila produces type 1 fimbriae on the surface of Phase I cells. Fimbriae mediate recognition and adhesion of the bacteria to its target cell. To investigate the role of fimbriae in the biology of X. nematophila, we have produced a fimbrial mutant strain by insertional inactivation of the mrxA gene, encoding the structural subunit of type 1 fimbriae. Phenotypic characterization of the mutant revealed loss of fimbriae on the cell surface. Cell surface characteristics like dye absorption, biofilm formation, red blood cell agglutination remained unaltered. The mrxA mutant was defective in swarming on soft agar, although swimming motility was not affected. Flagellar expression was suppressed in the mrxA strain under swarming conditions, but not swimming conditions. Agglutination and cytotoxicity of the mutant to larval haemocytes was also reduced. When the mutant cells were injected in the haemocoel of the fourth instar larvae of Helicoverpa armigera, an increase in the LT(50) of 9-12 h was observed relative to the wild-type strain. The nematode growth was slow on the lawn of the fimbrial mutant. The mrxA negative strain was unable to colonize the nematode gut efficiently. This study demonstrates importance of type 1 fimbriae in establishment of bacteria-nematode symbiosis, a key to successful pest management program.
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Affiliation(s)
- Harish Chandra
- International Centre for Genetic Engineering and Biotechnology, New Delhi 110067, India
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508
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Hsu JL, Chen HC, Peng HL, Chang HY. Characterization of the histidine-containing phosphotransfer protein B-mediated multistep phosphorelay system in Pseudomonas aeruginosa PAO1. J Biol Chem 2008; 283:9933-44. [PMID: 18256026 DOI: 10.1074/jbc.m708836200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Certain bacterial two-component sensor kinases possess a histidine-containing phosphotransfer (Hpt) domain to carry out a multistep phosphotransferring reaction to a cognate response regulator. Pseudomonas aeruginosa PAO1 contains three genes that encode proteins with an Hpt domain but lack a kinase domain. To identify the sensor kinase coupled to these Hpt proteins, a phosphorelay profiling assay was performed. Among the 12 recombinant orphan sensor kinases tested, 4 of these sensors (PA1611, PA1976, PA2824, and RetS) transferred the phosphoryl group to HptB (PA3345). The in vivo interaction between HptB and each of the sensors was also confirmed using the bacterial two-hybrid assay. Interestingly, the phosphoryl groups from these sensors all appeared to be transferred via HptB to PA3346, a novel phosphatase consisting of an N-terminal receiver domain and a eukaryotic type Ser/Thr phosphatase domain, and resulted in a significant increase of its phosphatase activity. The subsequent reverse transcription-PCR analysis revealed an operon structure of hptB-PA3346-PA3347, suggesting a coordinate expression of the three genes to carry out a signal transduction. The possibility was supported by the analysis showing PA3347 is able to be phosphorylated on Ser-56, and this phosphoryl group could be removed by PA3346 protein. Finally, analysis of PA3346 and PA3347 gene knock-out mutants revealed that these genes are associated with bacterial swarming activity and biofilm formation. Together, these results disclose a novel multistep phosphorelay system that is essential for P. aeruginosa to respond to a wide spectrum of environmental signals.
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Affiliation(s)
- Jye-Lin Hsu
- Institute of Molecular Medicine, National Tsing Hua University, 101 Guang Fu Road 2nd Section, Hsin Chu 300, Taiwan, Republic of China
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509
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Las-like quorum-sensing system negatively regulates both pyoluteorin and phenazine-1-carboxylic acid production in Pseudomonas sp. M18. ACTA ACUST UNITED AC 2008; 51:174-81. [DOI: 10.1007/s11427-008-0026-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2007] [Accepted: 10/16/2007] [Indexed: 11/26/2022]
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510
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Swarming of Pseudomonas aeruginosa is a complex adaptation leading to increased production of virulence factors and antibiotic resistance. J Bacteriol 2008; 190:2671-9. [PMID: 18245294 DOI: 10.1128/jb.01659-07] [Citation(s) in RCA: 274] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In addition to exhibiting swimming and twitching motility, Pseudomonas aeruginosa is able to swarm on semisolid (viscous) surfaces. Recent studies have indicated that swarming is a more complex type of motility influenced by a large number of different genes. To investigate the adaptation process involved in swarming motility, gene expression profiles were analyzed by performing microarrays on bacteria from the leading edge of a swarm zone compared to bacteria growing in identical medium under swimming conditions. Major shifts in gene expression patterns were observed under swarming conditions, including, among others, the overexpression of a large number of virulence-related genes such as those encoding the type III secretion system and its effectors, those encoding extracellular proteases, and those associated with iron transport. In addition, swarming cells exhibited adaptive antibiotic resistance against polymyxin B, gentamicin, and ciprofloxacin compared to what was seen for their planktonic (swimming) counterparts. By analyzing a large subset of up-regulated genes, we were able to show that two virulence genes, lasB and pvdQ, were required for swarming motility. These results clearly favored the conclusion that swarming of P. aeruginosa is a complex adaptation process in response to a viscous environment resulting in a substantial change in virulence gene expression and antibiotic resistance.
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511
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Takahashi C, Nozawa T, Tanikawa T, Nakagawa Y, Wakita J, Matsushita M, Matsuyama T. Swarming of Pseudomonas aeruginosa PAO1 without differentiation into elongated hyperflagellates on hard agar minimal medium. FEMS Microbiol Lett 2008; 280:169-75. [PMID: 18248427 DOI: 10.1111/j.1574-6968.2007.01057.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Polar flagellated Pseudomonas aeruginosa PAO1 demonstrated extensive spreading growth in 2 days on 1.5% agar medium. Such spreading growth of P. aeruginosa PAO1 strains was absent on Luria-Bertani 1.5% agar medium, but remarkable on Davis minimal synthetic agar medium (especially that containing 0.8% sodium citrate and 1.5% Eiken agar) under aerobic 37 degrees C conditions. Analyses using isogenic mutants and complementation transformants showed that bacterial flagella and rhamnolipid contributed to the surface-spreading behavior. On the other hand, a type IV pilus-deficient pilA mutant did not lose the spreading growth activity. Flagella staining of PAO1 T cells from the frontal edge of a spreading colony showed unipolar and normal-sized rods with one or two flagella. Thus, the polar flagellate P. aeruginosa PAO1 T appears to swarm on high-agar medium by producing biosurfactant rhamnolipid and without differentiation into an elongated peritrichous hyperflagellate.
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Affiliation(s)
- Chihiro Takahashi
- Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Niigata, Japan
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512
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Nozawa T, Tanikawa T, Hasegawa H, Takahashi C, Ando Y, Matsushita M, Nakagawa Y, Matsuyama T. Rhamnolipid-dependent spreading growth of Pseudomonas aeruginosa on a high-agar medium: marked enhancement under CO2-rich anaerobic conditions. Microbiol Immunol 2008; 51:703-12. [PMID: 17704632 DOI: 10.1111/j.1348-0421.2007.tb03959.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Anaerobiosis of Pseudomonas aeruginosa in infected organs is now gaining attention as a unique physiological feature. After anaerobic cultivation of P. aeruginosa wild type strain PAO1 T, we noticed an unexpectedly expanding colony on a 1.5% agar medium. The basic factors involved in this spreading growth were investigated by growing the PAO1 T strain and its isogenic mutants on a Davis high-agar minimal synthetic medium under various experimental conditions. The most promotive environment for this spreading growth was an O(2)-depleted 8% CO(2) condition. From mutational analysis of this spreading growth, flagella and type IV pili were shown to be ancillary factors for this bacterial activity. On the other hand, a rhamnolipid-deficient rhlA mutant TR failed to exhibit spreading growth on a high-agar medium. Complementation of the gene defect of the mutant TR with a plasmid carrying the rhlAB operon resulted in the restoration of the spreading growth. In addition, an external supply of rhamnolipid or other surfactants (surfactin from Bacillus subtilis or artificial product Tween 80) also restored the spreading growth of the mutant TR. Such activity of surfactants on bacterial spreading on a hard-agar medium was unique to P. aeruginosa under CO(2)-rich anaerobic conditions.
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Affiliation(s)
- Takashi Nozawa
- Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Niigata 950-2181, Japan
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513
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Tremblay J, Richardson AP, Lépine F, Déziel E. Self-produced extracellular stimuli modulate the Pseudomonas aeruginosa swarming motility behaviour. Environ Microbiol 2008; 9:2622-30. [PMID: 17803784 DOI: 10.1111/j.1462-2920.2007.01396.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pseudomonas aeruginosa presents three types of motilities: swimming, twitching and swarming. The latter is characterized by rapid and coordinated group movement over a semisolid surface resulting from morphological differentiation and intercellular interactions. A striking feature of P. aeruginosa swarming motility is the formation of migrating tendrils producing colonies with complex fractal-like patterns. Previous studies have shown that normal swarming motility is intimately related to the production of extracellular surface-active molecules: rhamnolipids (RLs), composed of monorhamnolipids (mono-RLs) and dirhamnolipids (di-RLs), and 3-(3-hydroxyalkanoyloxy) alkanoic acids (HAAs). Here, we report that (i) di-RLs attract active swarming cells while HAAs behave as strong repellents, (ii) di-RLs promote and HAAs inhibit tendril formation and migration, (iii) di-RLs and HAAs display different diffusion kinetics on a surface as di-RLs spread faster than HAAs in agar, (iv) di-RLs and HAAs have no effect on swimming cells, suggesting that swarming cells are different from swimming cells not only in morphology but also at the regulatory level and (v) mono-RLs act as wetting agents. We propose a model explaining how HAAs and di-RLs together modulate the behaviour of swarming migrating cells by acting as self-produced negative and positive chemotactic-like stimuli.
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Affiliation(s)
- Julien Tremblay
- INRS-Institut Armand-Frappier, Laval (Québec), H7V 1B7, Canada
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514
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Pseudomonas aeruginosa exhibits sliding motility in the absence of type IV pili and flagella. J Bacteriol 2007; 190:2700-8. [PMID: 18065549 DOI: 10.1128/jb.01620-07] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa exhibits swarming motility on 0.5 to 1% agar plates in the presence of specific carbon and nitrogen sources. We have found that PAO1 double mutants expressing neither flagella nor type IV pili (fliC pilA) display sliding motility under the same conditions. Sliding motility was inhibited when type IV pilus expression was restored; like swarming motility, it also decreased in the absence of rhamnolipid surfactant production. Transposon insertions in gacA and gacS increased sliding motility and restored tendril formation to spreading colonies, while transposon insertions in retS abolished motility. These changes in motility were not accompanied by detectable changes in rhamnolipid surfactant production or by the appearance of bacterial surface structures that might power sliding motility. We propose that P. aeruginosa requires flagella during swarming to overcome adhesive interactions mediated by type IV pili. The apparent dependence of sliding motility on environmental cues and regulatory pathways that also affect swarming motility suggests that both forms of motility are influenced by similar cohesive factors that restrict translocation, as well as by dispersive factors that facilitate spreading. Studies of sliding motility may be particularly well-suited for identifying factors other than pili and flagella that affect community behaviors of P. aeruginosa.
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515
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Transcriptional activity of Pseudomonas aeruginosa fhp promoter is dependent on two regulators in addition to FhpR. Arch Microbiol 2007; 189:385-96. [PMID: 18043907 DOI: 10.1007/s00203-007-0329-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Accepted: 11/09/2007] [Indexed: 12/22/2022]
Abstract
The regulation of flavohemoglobin expression is complex and depending on its host organism requires a wide variety of different transcriptional regulators. In Pseudomonas aeruginosa, the flavohemoglobin (Fhp) and its cognate regulator FhpR form an NO-sensing and detoxifying system regulated by their common bidirectional promoter Pfhp/PfhpR. The intergenic fhp-fhpR region of P. aeruginosa PAO1 was used as a bait to isolate proteins affecting the transcription of fhp and fhpR. In addition to the FhpR, we identified two previously uncharacterized P. aeruginosa proteins, PA0779 and PA3697. Both PA0779 and PA3697 were found to be essential for NO3(-) and NO2(-) induced Pfhp activity under aerobic and low-oxygen conditions, and needed for the full function of Pfhp/PfhpR as NO responsive regulatory circuit under aerobic conditions. In addition, we show that the transcriptional activity of PfhpR is highly inducible upon addition of SNP under aerobic conditions, but not by NO3(-), NO2(-) or under low-oxygen conditions, supporting the findings that FhpR is not the only factor affecting flavohemoglobin expression in P. aeruginosa.
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516
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Merritt JH, Brothers KM, Kuchma SL, O'Toole GA. SadC reciprocally influences biofilm formation and swarming motility via modulation of exopolysaccharide production and flagellar function. J Bacteriol 2007; 189:8154-64. [PMID: 17586642 PMCID: PMC2168701 DOI: 10.1128/jb.00585-07] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 06/11/2007] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa has served as an important organism in the study of biofilm formation; however, we still lack an understanding of the mechanisms by which this microbe transitions to a surface lifestyle. A recent study of the early stages of biofilm formation implicated the control of flagellar reversals and production of an exopolysaccharide (EPS) as factors in the establishment of a stable association with the substratum and swarming motility. Here we present evidence that SadC (PA4332), an inner membrane-localized diguanylate cyclase, plays a role in controlling these cellular functions. Deletion of the sadC gene results in a strain that is defective in biofilm formation and a hyperswarmer, while multicopy expression of this gene promotes sessility. A DeltasadC mutant was additionally found to be deficient in EPS production and display altered reversal behavior while swimming in high-viscosity medium, two behaviors proposed to influence biofilm formation and swarming motility. Epistasis analysis suggests that the sadC gene is part of a genetic pathway that allows for the concomitant regulation of these aspects of P. aeruginosa surface behavior. We propose that SadC and the phosphodiesterase BifA (S. L. Kuchma et al., J. Bacteriol. 189:8165-8178, 2007), via modulating levels of the signaling molecule cyclic-di-GMP, coregulate swarming motility and biofilm formation as P. aeruginosa transitions from a planktonic to a surface-associated lifestyle.
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Affiliation(s)
- Judith H Merritt
- Department of Microbiology and Immunology, Rm. 505, Vail Building, Dartmouth Medical School, Hanover, NH 03755, USA
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517
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Díaz C, Schilardi PL, Salvarezza RC, de Mele MFL. Nano/microscale order affects the early stages of biofilm formation on metal surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:11206-10. [PMID: 17880247 DOI: 10.1021/la700650q] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The adhesion of Pseudomonas fluorescens was studied on nano/microengineered surfaces. Results show that these bacteria formed well-defined aggregates on randomly oriented nanosized granular gold substrates. These aggregates consist of aligned ensembles of bacteria, with some of them strongly elongated. This kind of biological structure was not found on ordered engineered surfaces because bacterial alignment and cell-to-cell sticking were hindered. Importantly, differences in cell morphology, length, orientation, and flagellation were observed between bacteria attached on the ordered nano/microstructures and the randomly ordered surfaces. The implications of the results are related to the design of engineered surfaces to enhance (nanostructured filters) or inhibit (medical implants and industrial biofouling) bacterial colonization on the surfaces and to the biocontrol of soil ecosystems.
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Affiliation(s)
- C Díaz
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata-CONICET, Sucursal 4 Casilla de Correo 16, (1900) La Plata, Argentina
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518
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Lequette Y, Rollet E, Delangle A, Greenberg EP, Bohin JP. Linear osmoregulated periplasmic glucans are encoded by the opgGH locus of Pseudomonas aeruginosa. Microbiology (Reading) 2007; 153:3255-3263. [PMID: 17906125 DOI: 10.1099/mic.0.2007/008953-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Osmoregulated periplasmic glucans (OPGs) are produced by many proteobacteria and are important for bacterial-host interactions. The opgG and opgH genes involved in the synthesis of OPGs are the most widely distributed genes in proteobacterial genomes. Two other non-homologous genes, both named ndvB, are also involved in OPG biosynthesis in several species. The Pseudomonas aeruginosa genome possesses two ORFs, PA5077 and PA5078, that show similarity to opgH and opgG of Pseudomonas syringae, respectively, and one ORF, PA1163, similar to ndvB of Sinorhizobium meliloti. Here, we report that the opgGH locus of P. aeruginosa PA14 is involved in the synthesis of linear polymers with beta-1,2-linked glucosyl residues branched with a few beta-1,6 glucosyl residues. Succinyl residues also substitute this glucose backbone. Transcription of opgGH is repressed by high osmolarity. Low osmolarity promotes the formation of highly structured biofilms, but biofilm development is slower and the area of biomass is reduced under high osmolarity. Biofilm development of an opgGH mutant grown under low osmolarity presents a similar phenotype to the wild-type biofilm grown under high osmolarity. These results suggest that OPGs are important for biofilm formation under conditions of low osmolarity. A previous study suggested that the P. aeruginosa ndvB gene is involved in the resistance of biofilms to antibiotics. We have shown that ndvB is not involved in the biosynthesis of the OPG described here, and opgGH do not appear to be involved in the resistance of P. aeruginosa PA14 biofilms to antibiotics.
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Affiliation(s)
- Yannick Lequette
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Eglantine Rollet
- Unité de Glycobiologie Structurale et Fonctionnelle CNRS UMR 8576, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
| | - Aurélie Delangle
- Unité de Glycobiologie Structurale et Fonctionnelle CNRS UMR 8576, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
| | - E Peter Greenberg
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Jean-Pierre Bohin
- Unité de Glycobiologie Structurale et Fonctionnelle CNRS UMR 8576, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
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519
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Huang TP, Lee Wong AC. Extracellular fatty acids facilitate flagella-independent translocation by Stenotrophomonas maltophilia. Res Microbiol 2007; 158:702-11. [PMID: 18054205 DOI: 10.1016/j.resmic.2007.09.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/02/2007] [Accepted: 09/13/2007] [Indexed: 11/17/2022]
Abstract
Stenotrophomonas maltophilia is widespread in natural environments such as soil, sewage and plant rhizospheres. Surfactants frequently function in modulating bacterial surface translocation. In this study, rpfB and rpfF orthologues were identified from S. maltophilia strain WR-C, which was isolated from the clogged zone of a septic system. These genes play a role in the biosynthesis of eight extracellular compounds that facilitated flagella-independent translocation by the wild-type or a flagella-defective mutant. This type of surface translocation has not been reported previously for this organism. These eight compounds include cis-delta 2-11-methyl-dodecenoic acid and seven structural derivatives. Two are saturated fatty acids; the others are unsaturated fatty acids with double bonds at position 2. These fatty acids vary in chain length from 12 to 14 carbons and in the position of the branched methyl group. Our results demonstrated that independently cis-delta 2-11-methyl-dodecenoic acid and 11-methyl-dodecanoic acid promoted flagella-independent translocation by S. maltophilia strain WR-C by acting as wetting agents.
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Affiliation(s)
- Tzu-Pi Huang
- Department of Food Microbiology and Toxicology, University of Wisconsin-Madison, 1925 Willow Drive, Madison, WI 53706, USA.
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520
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Köhler T, Dumas JL, Van Delden C. Ribosome protection prevents azithromycin-mediated quorum-sensing modulation and stationary-phase killing of Pseudomonas aeruginosa. Antimicrob Agents Chemother 2007; 51:4243-8. [PMID: 17876004 PMCID: PMC2167979 DOI: 10.1128/aac.00613-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Pseudomonas aeruginosa, azithromycin has been shown to reduce virulence factor production, to retard biofilm formation, and to exhibit bactericidal effects on stationary-phase cells. In this study we analyzed whether these azithromycin-mediated effects require interaction with the ribosome. We blocked the access of azithromycin to the ribosome in P. aeruginosa PAO1 by expressing the 23S rRNA methylase ErmBP from Clostridium perfringens. Ribosome protection prevented the azithromycin-mediated reduction of elastase and rhamnolipid production, as well as the inhibition of swarming motility. Ribosome protection also prevented the killing of stationary-phase cells, suggesting that the cell-killing effect of azithromycin does not result solely from membrane destabilization. We further show that rhamnolipids are involved in cell killing, probably by increasing the uptake of the hydrophobic azithromycin molecule. These results have important implications for the treatment with azithromycin of patients chronically colonized by P. aeruginosa and might explain the variability in the efficacy of azithromycin treatments.
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Affiliation(s)
- Thilo Köhler
- Department of Microbiology and Molecular Medicine, University of Geneva, Centre Médical Universitaire, 1, rue Michel-Servet, CH-1211 Geneva 4, Switzerland.
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521
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Fonseca AP, Correia P, Sousa JC, Tenreiro R. Association patterns of Pseudomonas aeruginosa clinical isolates as revealed by virulence traits, antibiotic resistance, serotype and genotype. ACTA ACUST UNITED AC 2007; 51:505-16. [PMID: 17877730 DOI: 10.1111/j.1574-695x.2007.00328.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aims of this study were to assess the association patterns of 96 clinical isolates of Pseudomonas aeruginosa using hierarchical cluster analysis from data obtained from the measurement of the physicochemical cell surface properties, adhesion and initial biofilm formation abilities, to investigate any correspondence with source, serotype, beta-lactam pattern, motility and M13-PCR genogroup or clonal lineage, as well as to select clinical isolates that could act as representatives of the genotypic and phenotypic diversity of this P. aeruginosa population from a Portuguese Central Hospital. The isolates were phenotypically characterized by their ability to adhere and form biofilms on polystyrene surfaces, their affinity to hexadecane and silicone, their swimming and twitching abilities, their antibiotic susceptibility patterns and their serotypes. No particular phenotypic cluster associated with the same source, serotype, beta-lactam pattern, motility and M13-PCR genogroup and clonal lineage was found. Nevertheless, five representative strains of the P. aeruginosa population from this Hospital, selected on the basis of low genetic similarity, were also found to be dispersed among the phenotypic clusters.
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Affiliation(s)
- António Pedro Fonseca
- Serviço e Laboratório de Microbiologia, Faculdade de Medicina, Universidade do Porto, Alameda Professor Hernâni Monteiro, Porto, Portugal.
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522
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Palmer KL, Aye LM, Whiteley M. Nutritional cues control Pseudomonas aeruginosa multicellular behavior in cystic fibrosis sputum. J Bacteriol 2007; 189:8079-87. [PMID: 17873029 PMCID: PMC2168676 DOI: 10.1128/jb.01138-07] [Citation(s) in RCA: 445] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The sputum (mucus) layer of the cystic fibrosis (CF) lung is a complex substrate that provides Pseudomonas aeruginosa with carbon and energy to support high-density growth during chronic colonization. Unfortunately, the CF lung sputum layer has been difficult to mimic in animal models of CF disease, and mechanistic studies of P. aeruginosa physiology during growth in CF sputum are hampered by its complexity. In this study, we performed chromatographic and enzymatic analyses of CF sputum to develop a defined, synthetic CF sputum medium (SCFM) that mimics the nutritional composition of CF sputum. Importantly, P. aeruginosa displays similar phenotypes during growth in CF sputum and in SCFM, including similar growth rates, gene expression profiles, carbon substrate preferences, and cell-cell signaling profiles. Using SCFM, we provide evidence that aromatic amino acids serve as nutritional cues that influence cell-cell signaling and antimicrobial activity of P. aeruginosa during growth in CF sputum.
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Affiliation(s)
- Kelli L Palmer
- Section of Molecular Genetics and Microbiology, University of Texas at Austin, 1 University Station, A5000, Austin, TX 78712, USA
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523
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Morici LA, Carterson AJ, Wagner VE, Frisk A, Schurr JR, Höner zu Bentrup K, Hassett DJ, Iglewski BH, Sauer K, Schurr MJ. Pseudomonas aeruginosa AlgR represses the Rhl quorum-sensing system in a biofilm-specific manner. J Bacteriol 2007; 189:7752-64. [PMID: 17766417 PMCID: PMC2168728 DOI: 10.1128/jb.01797-06] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
AlgR controls numerous virulence factors in Pseudomonas aeruginosa, including alginate, hydrogen cyanide production, and type IV pilus-mediated twitching motility. In this study, the role of AlgR in biofilms was examined in continuous-flow and static biofilm assays. Strain PSL317 (DeltaalgR) produced one-third the biofilm biomass of wild-type strain PAO1. Complementation with algR, but not fimTU-pilVWXY1Y2E, restored PSL317 to the wild-type biofilm phenotype. Comparisons of the transcriptional profiles of biofilm-grown PAO1 and PSL317 revealed that a number of quorum-sensing genes were upregulated in the algR deletion strain. Measurement of rhlA::lacZ and rhlI::lacZ promoter fusions confirmed the transcriptional profiling data when PSL317 was grown as a biofilm, but not planktonically. Increased amounts of rhamnolipids and N-butyryl homoserine lactone were detected in the biofilm effluent but not the planktonic supernatants of the algR mutant. Additionally, AlgR specifically bound to the rhlA and rhlI promoters in mobility shift assays. Moreover, PAO1 containing a chromosomal mutated AlgR binding site in its rhlI promoter formed biofilms and produced increased amounts of rhamnolipids similarly to the algR deletion strain. These observations indicate that AlgR specifically represses the Rhl quorum-sensing system during biofilm growth and that such repression is necessary for normal biofilm development. These data also suggest that AlgR may control transcription in a contact-dependent or biofilm-specific manner.
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Affiliation(s)
- Lisa A Morici
- Tulane University Health Sciences Center, Department of Microbiology and Immunology, New Orleans, LA 70112, USA
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524
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Lasocki K, Bartosik AA, Mierzejewska J, Thomas CM, Jagura-Burdzy G. Deletion of the parA (soj) homologue in Pseudomonas aeruginosa causes ParB instability and affects growth rate, chromosome segregation, and motility. J Bacteriol 2007; 189:5762-72. [PMID: 17545287 PMCID: PMC1951838 DOI: 10.1128/jb.00371-07] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 05/22/2007] [Indexed: 11/20/2022] Open
Abstract
The parA and parB genes of Pseudomonas aeruginosa are located approximately 8 kb anticlockwise from oriC. ParA is a cytosolic protein present at a level of around 600 molecules per cell in exponential phase, but the level drops about fivefold in stationary phase. Overproduction of full-length ParA or the N-terminal 85 amino acids severely inhibits growth of P. aeruginosa and P. putida. Both inactivation of parA and overexpression of parA in trans in P. aeruginosa also lead to accumulation of anucleate cells and changes in motility. Inactivation of parA also increases the turnover rate (degradation) of ParB. This may provide a mechanism for controlling the level of ParB in response to the growth rate and expression of the parAB operon.
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Affiliation(s)
- Krzysztof Lasocki
- The Institute of Biochemistry and Biophysics, PAS, 02-106 Warsaw, Pawinskiego 5A, Poland
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525
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Wilhelm S, Gdynia A, Tielen P, Rosenau F, Jaeger KE. The autotransporter esterase EstA of Pseudomonas aeruginosa is required for rhamnolipid production, cell motility, and biofilm formation. J Bacteriol 2007; 189:6695-703. [PMID: 17631636 PMCID: PMC2045186 DOI: 10.1128/jb.00023-07] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa PAO1 produces the biodetergent rhamnolipid and secretes it into the extracellular environment. The role of rhamnolipids in the life cycle and pathogenicity of P. aeruginosa has not been completely understood, but they are known to affect outer membrane composition, cell motility, and biofilm formation. This report is focused on the influence of the outer membrane-bound esterase EstA of P. aeruginosa PAO1 on rhamnolipid production. EstA is an autotransporter protein which exposes its catalytically active esterase domain on the cell surface. Here we report that the overexpression of EstA in the wild-type background of P. aeruginosa PAO1 results in an increased production of rhamnolipids whereas an estA deletion mutant produced only marginal amounts of rhamnolipids. Also the known rhamnolipid-dependent cellular motility and biofilm formation were affected. Although only a dependence of swarming motility on rhamnolipids has been known so far, the other kinds of motility displayed by P. aeruginosa PAO1, swimming and twitching, were also affected by an estA mutation. In order to demonstrate that EstA enzyme activity is responsible for these effects, inactive variant EstA* was constructed by replacement of the active serine by alanine. None of the mutant phenotypes could be complemented by expression of EstA*, demonstrating that the phenotypes affected by the estA mutation depend on the enzymatically active protein.
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Affiliation(s)
- Susanne Wilhelm
- Institute for Molecular Enzyme Technology, Heinrich Heine University Duesseldorf, Research Centre Juelich, Stetternicher Forst, D-52426 Juelich, Germany
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526
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Boşgelmez-Tinaz G, Ulusoy S. Characterization of N-butanoyl-L-homoserine lactone (C4-HSL) deficient clinical isolates of Pseudomonas aeruginosa. Microb Pathog 2007; 44:13-9. [PMID: 17689222 DOI: 10.1016/j.micpath.2007.06.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Accepted: 06/13/2007] [Indexed: 10/23/2022]
Abstract
In the opportunistic pathogen Pseudomonas aeruginosa, the production of several virulence factors such as elastase, rhamnolipids and pyocyanin depends on cell-to-cell signaling or quorum sensing (QS) involving N-acylhomoserine lactone (AHL) signal molecules. In vitro studies with laboratory strains and virulence studies in animals with these same strains have demonstrated the contribution of QS to the pathogenesis of P. aeruginosa. However, the importance of P. aeruginosa QS systems in the development of human infections is not clearly known. In order to determine if deficiency within the QS system compromises the ability of P. aeruginosa to cause infections in humans, we collected 50 P. aeruginosa clinical isolates. Phenotypic characterization showed that isolates I-457, I-458, I-459 and I-461 were defective in the production of N-butanoyl-l-homoserine lactone (C4-HSL) signaling molecule and virulence factors elastase, protease, pyocyanin and rhamnolipids. Analysis of the sequences of the lasR, lasI, rhlR and rhlI genes of these four isolates showed that two of the four isolates had mutational defects in both rhlR and rhlI genes while other two isolates were only mutated in the rhlI gene. The combination of rhlR and rhlI mutations or only rhlI mutation probably explains their C4-HSL and virulence factors deficiencies. These observations suggest that QS deficient P. aeruginosa clinical isolates are able to cause infections and that in addition to known virulence factors, factors yet unidentified may contribute to the pathogenesis of P. aeruginosa.
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527
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Li Y, Xia H, Bai F, Xu H, Yang L, Yao H, Zhang L, Zhang X, Bai Y, Saris PEJ, Tolker-Nielsen T, Qiao M. Identification of a new genePA5017involved in flagella-mediated motility, chemotaxis and biofilm formation inPseudomonas aeruginosa. FEMS Microbiol Lett 2007; 272:188-95. [PMID: 17521365 DOI: 10.1111/j.1574-6968.2007.00753.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Flagella-mediated motility is recognized as one of the major factors contributing to virulence in Pseudomonas aeruginosa. During a screening of a mini-Mu transposon mutant library of P. aeruginosa PA68, a mutant partially deficient in swimming and swarming motility was identified in a new locus that encodes a predicted protein of unknown function annotated PA5017 in the P. aeruginosa PAO1 genome sequence. Chemotaxis plate assay indicated that inactivation of the PA5017 gene led to a decreased chemotactic response. Complementation of the PA5017 mutant with the wild-type PA5017 gene restored normal motility and chemotaxis phenotype. A promoter-lacZ reporter activity assay of the cheYZAB operon from chemotaxis gene cluster 1 showed that there was almost a twofold difference in expression levels of the wild-type PA68 and the PA5017 mutant. This suggested that the PA5017 affected expression of the cheYZAB operon negatively. Further study showed that inactivation of the PA5017 gene in PA68 led to increased biofilm formation in a static system and to the formation of a heterogeneous biofilm in a flow-chamber system. These results suggested that PA5017 possibly affected flagellum-dependent motility and in turn biofilm formation via the chemotaxis signal transduction pathway.
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MESH Headings
- Artificial Gene Fusion
- Biofilms
- Chemotaxis/genetics
- DNA Transposable Elements
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- Flagella/genetics
- Flagella/ultrastructure
- Gene Deletion
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Genes, Reporter
- Genetic Complementation Test
- Locomotion/genetics
- Microscopy, Electron, Scanning
- Microscopy, Electron, Transmission
- Molecular Sequence Data
- Mutagenesis, Insertional
- Operon
- Pseudomonas aeruginosa/genetics
- Pseudomonas aeruginosa/physiology
- Sequence Analysis, DNA
- beta-Galactosidase/analysis
- beta-Galactosidase/genetics
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Affiliation(s)
- Yingli Li
- College of Life Sciences, Nankai University, Tianjin, China
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528
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Abstract
Many bacteria simultaneously grow and spread rapidly over a surface that supplies them with nutrient. Called 'swarming', this pattern of movement directs new cells to the edge of the colony. Swarming reduces competition between cells for nutrients, speeding growth. Behind the swarm edge, where the cell density is higher, growth is limited by transport of nutrient from the subsurface to the overlying cells. Despite years of study, the choreography of swarm cell movement, the bacterial equivalent of dancing toward an exit in a very dense crowd of moving bodies, remains a mystery. Swarming can be propelled by rotating flagella, and either by pulling with type IV pili or by pushing with the secretion of slime. By identifying patterns of movement that are common to swarms making use of different engines, a model of swarm choreography can be proposed.
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Affiliation(s)
- Dale Kaiser
- Departments of Biochemistry and Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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529
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Kuchma SL, Brothers KM, Merritt JH, Liberati NT, Ausubel FM, O'Toole GA. BifA, a cyclic-Di-GMP phosphodiesterase, inversely regulates biofilm formation and swarming motility by Pseudomonas aeruginosa PA14. J Bacteriol 2007; 189:8165-78. [PMID: 17586641 PMCID: PMC2168662 DOI: 10.1128/jb.00586-07] [Citation(s) in RCA: 277] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The intracellular signaling molecule, cyclic-di-GMP (c-di-GMP), has been shown to influence bacterial behaviors, including motility and biofilm formation. We report the identification and characterization of PA4367, a gene involved in regulating surface-associated behaviors in Pseudomonas aeruginosa. The PA4367 gene encodes a protein with an EAL domain, associated with c-di-GMP phosphodiesterase activity, as well as a GGDEF domain, which is associated with a c-di-GMP-synthesizing diguanylate cyclase activity. Deletion of the PA4367 gene results in a severe defect in swarming motility and a hyperbiofilm phenotype; thus, we designate this gene bifA, for biofilm formation. We show that BifA localizes to the inner membrane and, in biochemical studies, that purified BifA protein exhibits phosphodiesterase activity in vitro but no detectable diguanylate cyclase activity. Furthermore, mutational analyses of the conserved EAL and GGDEF residues of BifA suggest that both domains are important for the observed phosphodiesterase activity. Consistent with these data, the DeltabifA mutant exhibits increased cellular pools of c-di-GMP relative to the wild type and increased synthesis of a polysaccharide produced by the pel locus. This increased polysaccharide production is required for the enhanced biofilm formed by the DeltabifA mutant but does not contribute to the observed swarming defect. The DeltabifA mutation also results in decreased flagellar reversals. Based on epistasis studies with the previously described sadB gene, we propose that BifA functions upstream of SadB in the control of biofilm formation and swarming.
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Affiliation(s)
- Sherry L Kuchma
- Department of Microbiology and Immunology, Dartmouth Medical School, Rm. 505, Vail Building, North College St., Hanover, NH 03755, USA
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530
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Fonseca A, Sousa J. Effect of antibiotic-induced morphological changes on surface properties, motility and adhesion of nosocomial Pseudomonas aeruginosa strains under different physiological states. J Appl Microbiol 2007; 103:1828-37. [DOI: 10.1111/j.1365-2672.2007.03422.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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531
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Schaber JA, Hammond A, Carty NL, Williams SC, Colmer-Hamood JA, Burrowes BH, Dhevan V, Griswold JA, Hamood AN. Diversity of biofilms produced by quorum-sensing-deficient clinical isolates of Pseudomonas aeruginosa. J Med Microbiol 2007; 56:738-748. [PMID: 17510257 DOI: 10.1099/jmm.0.47031-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The quorum-sensing (QS) systems control several virulence attributes of Pseudomonas aeruginosa. Five QS-deficient P. aeruginosa clinical isolates (CI) that were obtained from wound (CI-1), tracheal (CI-2, CI-3, CI-4) and urinary tract (CI-5) infections had previously been characterized. In this study, a flow-through continuous-culture system was utilized to examine in detail the biofilms formed by these isolates in comparison with the P. aeruginosa prototrophic strain PAO1. Analysis of the biofilms by confocal laser scanning microscopy and COMSTAT image analysis at 1 and 7 days post-inoculation showed that the isolates produced diverse biofilms. In comparison with PAO1, the CI produced biofilms that scarcely or partially covered the surface at day 1, although CI-1 produced larger microcolonies. At day 7, CI-2 and CI-4 produced mature biofilms denser than that produced by PAO1, while the biofilm formed by CI-1 changed very little from day 1. CI-1 was defective in both swarming and twitching motilities, and immunoblotting analysis confirmed that it produced a reduced level of PilA protein. The twitching-motility defect of CI-1 was not complemented by a plasmid carrying intact pilA. In the 48 h colony biofilm assay, the CI varied in susceptibility to imipenem, gentamicin and piperacillin/tazobactam. These results suggest that: (1) the isolates produced biofilms with different structures and densities from that of PAO1; (2) biofilm formation by the isolates was not influenced by either the isolation site or the QS deficiencies of the isolates; (3) the behaviour of CI-1 in the different biofilm systems may be due to its lack of swarming motility and type IV pilus-related twitching motility.
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Affiliation(s)
- J Andy Schaber
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Adrienne Hammond
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Nancy L Carty
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Simon C Williams
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Jane A Colmer-Hamood
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Ben H Burrowes
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Vijian Dhevan
- School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - John A Griswold
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Abdul N Hamood
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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532
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Van Alst NE, Picardo KF, Iglewski BH, Haidaris CG. Nitrate sensing and metabolism modulate motility, biofilm formation, and virulence in Pseudomonas aeruginosa. Infect Immun 2007; 75:3780-90. [PMID: 17526746 PMCID: PMC1952006 DOI: 10.1128/iai.00201-07] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infection by the bacterial opportunist Pseudomonas aeruginosa frequently assumes the form of a biofilm, requiring motility for biofilm formation and dispersal and an ability to grow in nutrient- and oxygen-limited environments. Anaerobic growth by P. aeruginosa is accomplished through the denitrification enzyme pathway that catalyzes the sequential reduction of nitrate to nitrogen gas. Mutants mutated in the two-component nitrate sensor-response regulator and in membrane nitrate reductase displayed altered motility and biofilm formation compared to wild-type P. aeruginosa PAO1. Analysis of additional nitrate dissimilation mutants demonstrated a second level of regulation in P. aeruginosa motility that is independent of nitrate sensor-response regulator function and is associated with nitric oxide production. Because motility and biofilm formation are important for P. aeruginosa pathogenicity, we examined the virulence of selected regulatory and structural gene mutants in the surrogate model host Caenorhabditis elegans. Interestingly, the membrane nitrate reductase mutant was avirulent in C. elegans, while nitrate sensor-response regulator mutants were fully virulent. The data demonstrate that nitrate sensing, response regulation, and metabolism are linked directly to factors important in P. aeruginosa pathogenesis.
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Affiliation(s)
- Nadine E Van Alst
- Department of Microbiology and Immunology, Box 672, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA
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533
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Caiazza NC, Merritt JH, Brothers KM, O'Toole GA. Inverse regulation of biofilm formation and swarming motility by Pseudomonas aeruginosa PA14. J Bacteriol 2007; 189:3603-12. [PMID: 17337585 PMCID: PMC1855903 DOI: 10.1128/jb.01685-06] [Citation(s) in RCA: 214] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Accepted: 02/15/2007] [Indexed: 11/20/2022] Open
Abstract
We previously reported that SadB, a protein of unknown function, is required for an early step in biofilm formation by the opportunistic pathogen Pseudomonas aeruginosa. Here we report that a mutation in sadB also results in increased swarming compared to the wild-type strain. Our data are consistent with a model in which SadB inversely regulates biofilm formation and swarming motility via its ability both to modulate flagellar reversals in a viscosity-dependent fashion and to influence the production of the Pel exopolysaccharide. We also show that SadB is required to properly modulate flagellar reversal rates via chemotaxis cluster IV (CheIV cluster). Mutational analyses of two components of the CheIV cluster, the methyl-accepting chemotaxis protein PilJ and the PilJ demethylase ChpB, support a model wherein this chemotaxis cluster participates in the inverse regulation of biofilm formation and swarming motility. Epistasis analysis indicates that SadB functions upstream of the CheIV cluster. We propose that P. aeruginosa utilizes a SadB-dependent, chemotaxis-like regulatory pathway to inversely regulate two key surface behaviors, biofilm formation and swarming motility.
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Affiliation(s)
- Nicky C Caiazza
- Dept. of Microbiology & Immunology, Rm. 505, Vail Building, Dartmouth Medical School, Hanover, NH 03755, USA
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534
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Hasegawa H, Tanikawa T, Nozawa T, Nakazawa K, Nakagawa Y, Matsuyama T. Distinct function of Pseudomonas aeruginosa type IV pili disclosed in the bacterial pass-through of membrane filter with smaller pore sizes. Microbiol Immunol 2007; 51:429-33. [PMID: 17446682 DOI: 10.1111/j.1348-0421.2007.tb03930.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Membrane filter pass-through ability of Pseudomonas aeruginosa was analyzed with isogenic mutants. A flagellum-deficient fliC mutant required two-times longer time (12 hr) to pass through a 0.45-microm pore size filter. With 0.3- and 0.22-microm filters, however, the fliC mutant showed no remarkable disability. Meanwhile a pilA mutant defective in twitching motility failed to pass through the 0.22-microm filter. Complementation of the mutant with pilA gene on a plasmid restored the twitching motility and the 0.22-microm filter pass-through activity. Thus, the distinctive role of P. aeruginosa type IV pili in infiltration into finer reticulate structures was indicated.
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Affiliation(s)
- Hiroyuki Hasegawa
- Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Niigata, Japan
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535
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Toutain CM, Caizza NC, Zegans ME, O'Toole GA. Roles for flagellar stators in biofilm formation by Pseudomonas aeruginosa. Res Microbiol 2007; 158:471-7. [PMID: 17533122 DOI: 10.1016/j.resmic.2007.04.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 04/02/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
While Pseudomonas aeruginosa has only a single flagellum, its genome encodes two flagellar stators, called MotAB and MotCD. Here we report that despite no apparent alterations in swimming motility, mutations in either the MotAB or the MotCD stator render the strains defective for biofilm formation in both static and flow cell systems. Our data suggest distinct roles for the stators in early biofilm formation, with both the MotAB and MotCD stators playing a role in initial polar attachment of the bacterial cell to the surface (reversible attachment) and the MotAB stator also participating in the downstream adherence event of irreversible attachment. We also show that the initial polar attachment of P. aeruginosa to two different abiotic surfaces occurs largely at the flagellated end of the cell, a finding that should help develop models for early attachment events. Interestingly, in flowing conditions, a mutation in either stator alone revealed a more severe biofilm defect than mutating both stators or mutating the flagellum. Our data suggest that defects in biofilm formation observed for the stator mutants may be in part due to impacting flagellar reversal rates.
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Affiliation(s)
- Christine M Toutain
- Department of Microbiology and Immunology, Rm 505 Vail Building, N. College St., Dartmouth Medical School, Hanover, NH 03755, USA
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536
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Gómez-Gómez JM, Manfredi C, Alonso JC, Blázquez J. A novel role for RecA under non-stress: promotion of swarming motility in Escherichia coli K-12. BMC Biol 2007; 5:14. [PMID: 17391508 PMCID: PMC1852089 DOI: 10.1186/1741-7007-5-14] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Accepted: 03/28/2007] [Indexed: 12/23/2022] Open
Abstract
Background Bacterial motility is a crucial factor in the colonization of natural environments. Escherichia coli has two flagella-driven motility types: swimming and swarming. Swimming motility consists of individual cell movement in liquid medium or soft semisolid agar, whereas swarming is a coordinated cellular behaviour leading to a collective movement on semisolid surfaces. It is known that swimming motility can be influenced by several types of environmental stress. In nature, environmentally induced DNA damage (e.g. UV irradiation) is one of the most common types of stress. One of the key proteins involved in the response to DNA damage is RecA, a multifunctional protein required for maintaining genome integrity and the generation of genetic variation. Results The ability of E. coli cells to develop swarming migration on semisolid surfaces was suppressed in the absence of RecA. However, swimming motility was not affected. The swarming defect of a ΔrecA strain was fully complemented by a plasmid-borne recA gene. Although the ΔrecA cells grown on semisolidsurfaces exhibited flagellar production, they also presented impaired individual movement as well as a fully inactive collective swarming migration. Both the comparative analysis of gene expression profiles in wild-type and ΔrecA cells grown on a semisolid surface and the motility of lexA1 [Ind-] mutant cells demonstrated that the RecA effect on swarming does not require induction of the SOS response. By using a RecA-GFP fusion protein we were able to segregate the effect of RecA on swarming from its other functions. This protein fusion failed to regulate the induction of the SOS response, the recombinational DNA repair of UV-treated cells and the genetic recombination, however, it was efficient in rescuing the swarming motility defect of the ΔrecA mutant. The RecA-GFP protein retains a residual ssDNA-dependent ATPase activity but does not perform DNA strand exchange. Conclusion The experimental evidence presented in this work supports a novel role for RecA: the promotion of swarming motility. The defective swarming migration of ΔrecA cells does not appear to be associated with defective flagellar production; rather, it seems to be associated with an abnormal flagellar propulsion function. Our results strongly suggest that the RecA effect on swarming motility does not require an extensive canonical RecA nucleofilament formation. RecA is the first reported cellular factor specifically affecting swarming but not swimming motility in E. coli. The integration of two apparently disconnected biologically important processes, such as the maintenance of genome integrity and motility in a unique protein, may have important evolutive consequences.
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Affiliation(s)
- José-María Gómez-Gómez
- Departamento de Biotecnología Microbiana. Centro Nacional de Biotecnología, C/Darwin, 3, 28049-Madrid, Spain
| | - Candela Manfredi
- Departamento de Biotecnología Microbiana. Centro Nacional de Biotecnología, C/Darwin, 3, 28049-Madrid, Spain
| | - Juan-Carlos Alonso
- Departamento de Biotecnología Microbiana. Centro Nacional de Biotecnología, C/Darwin, 3, 28049-Madrid, Spain
| | - Jesús Blázquez
- Departamento de Biotecnología Microbiana. Centro Nacional de Biotecnología, C/Darwin, 3, 28049-Madrid, Spain
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537
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Marr AK, Overhage J, Bains M, Hancock REW. The Lon protease of Pseudomonas aeruginosa is induced by aminoglycosides and is involved in biofilm formation and motility. Microbiology (Reading) 2007; 153:474-482. [PMID: 17259618 DOI: 10.1099/mic.0.2006/002519-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is an important nosocomial opportunistic human pathogen and a major cause of chronic lung infections in individuals with cystic fibrosis. Serious infections by this organism are often treated with a combination of aminoglycosides and semi-synthetic penicillins. Subinhibitory concentrations of antibiotics are now being recognized for their role in microbial persistence and the development of antimicrobial resistance, two very important clinical phenomena. An extensive screen of a P. aeruginosa PAO1 luciferase gene fusion library was performed to identify genes that were differentially regulated during exposure to subinhibitory gentamicin. It was demonstrated that subinhibitory concentrations of gentamicin and tobramycin induced a set of genes that are likely to affect the interaction of P. aeruginosa with host cells, including the gene encoding Lon protease, which is known to play a major role in protein quality control. Studies with a lon mutant compared to its parent and a complemented strain indicated that this protein was essential for biofilm formation and motility in P. aeruginosa.
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Affiliation(s)
- Alexandra K Marr
- Centre for Microbial Diseases and Immunity Research, University of British Columbia, 2259 Lower Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Joerg Overhage
- Centre for Microbial Diseases and Immunity Research, University of British Columbia, 2259 Lower Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Manjeet Bains
- Centre for Microbial Diseases and Immunity Research, University of British Columbia, 2259 Lower Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | - Robert E W Hancock
- Centre for Microbial Diseases and Immunity Research, University of British Columbia, 2259 Lower Mall, Vancouver, British Columbia V6T 1Z4, Canada
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538
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Inoue T, Shingaki R, Hirose S, Waki K, Mori H, Fukui K. Genome-wide screening of genes required for swarming motility in Escherichia coli K-12. J Bacteriol 2007; 189:950-7. [PMID: 17122336 PMCID: PMC1797309 DOI: 10.1128/jb.01294-06] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 11/14/2006] [Indexed: 02/07/2023] Open
Abstract
Escherichia coli K-12 has the ability to migrate on semisolid media by means of swarming motility. A systematic and comprehensive collection of gene-disrupted E. coli K-12 mutants (the Keio collection) was used to identify the genes involved in the swarming motility of this bacterium. Of the 3,985 nonessential gene mutants, 294 were found to exhibit a strongly repressed-swarming phenotype. Further, 216 of the 294 mutants displayed no significant defects in swimming motility; therefore, the 216 genes were considered to be specifically associated with the swarming phenotype. The swarming-associated genes were classified into various functional categories, indicating that swarming is a specialized form of motility that requires a wide variety of cellular activities. These genes include genes for tricarboxylic acid cycle and glucose metabolism, iron acquisition, chaperones and protein-folding catalysts, signal transduction, and biosynthesis of cell surface components, such as lipopolysaccharide, the enterobacterial common antigen, and type 1 fimbriae. Lipopolysaccharide and the enterobacterial common antigen may be important surface-acting components that contribute to the reduction of surface tension, thereby facilitating the swarm migration in the E. coli K-12 strain.
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MESH Headings
- Antigens, Bacterial/genetics
- Antigens, Bacterial/physiology
- Citric Acid Cycle/genetics
- Citric Acid Cycle/physiology
- Escherichia coli/genetics
- Escherichia coli/physiology
- Escherichia coli/ultrastructure
- Escherichia coli Proteins/chemistry
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/physiology
- Fimbriae, Bacterial/chemistry
- Fimbriae, Bacterial/genetics
- Fimbriae, Bacterial/physiology
- Gene Deletion
- Genes, Bacterial
- Genome, Bacterial
- Glucose/metabolism
- Microscopy, Electron, Transmission
- Molecular Chaperones/genetics
- Molecular Chaperones/physiology
- Polysaccharides, Bacterial/metabolism
- Protein Folding
- Signal Transduction/genetics
- Signal Transduction/physiology
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Affiliation(s)
- Tetsuyoshi Inoue
- Department of Oral Microbiology, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, 2-5-1, Shikata, Okayama 700-8525, Japan.
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539
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Pamp SJ, Tolker-Nielsen T. Multiple roles of biosurfactants in structural biofilm development by Pseudomonas aeruginosa. J Bacteriol 2007; 189:2531-9. [PMID: 17220224 PMCID: PMC1899385 DOI: 10.1128/jb.01515-06] [Citation(s) in RCA: 264] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent studies have indicated that biosurfactants produced by Pseudomonas aeruginosa play a role both in maintaining channels between multicellular structures in biofilms and in dispersal of cells from biofilms. Through the use of flow cell technology and enhanced confocal laser scanning microscopy, we have obtained results which suggest that the biosurfactants produced by P. aeruginosa play additional roles in structural biofilm development. We present genetic evidence that during biofilm development by P. aeruginosa, biosurfactants promote microcolony formation in the initial phase and facilitate migration-dependent structural development in the later phase. P. aeruginosa rhlA mutants, deficient in synthesis of biosurfactants, were not capable of forming microcolonies in the initial phase of biofilm formation. Experiments involving two-color-coded mixed-strain biofilms showed that P. aeruginosa rhlA mutants were defective in migration-dependent development of mushroom-shaped multicellular structures in the later phase of biofilm formation. Experiments involving three-color-coded mixed-strain P. aeruginosa biofilms demonstrated that the wild-type and rhlA and pilA mutant strains formed distinct subpopulations on top of each other dependent on their ability to migrate and produce biosurfactants.
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Affiliation(s)
- Sünje Johanna Pamp
- Centre for BioScience Technology, BioCentrum-DTU, Building 301, The Technical University of Denmark, DK-2800 Lyngby, Denmark
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540
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Overhage J, Lewenza S, Marr AK, Hancock REW. Identification of genes involved in swarming motility using a Pseudomonas aeruginosa PAO1 mini-Tn5-lux mutant library. J Bacteriol 2006; 189:2164-9. [PMID: 17158671 PMCID: PMC1855721 DOI: 10.1128/jb.01623-06] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
During a screening of a mini-Tn5-luxCDABE transposon mutant library of Pseudomonas aeruginosa PAO1 for alterations in swarming motility, 36 mutants were identified with Tn5 insertions in genes for the synthesis or function of flagellin and type IV pilus, in genes for the Xcp-related type II secretion system, and in regulatory, metabolic, chemosensory, and hypothetical genes with unknown functions. These mutants were differentially affected in swimming and twitching motility but in most cases had only a minor additional motility defect. Our data provide evidence that swarming is a more complex type of motility, since it is influenced by a large number of different genes in P. aeruginosa. Conversely, many of the swarming-negative mutants also showed an impairment in biofilm formation, indicating a strong relationship between these types of growth states.
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Affiliation(s)
- Joerg Overhage
- Centre for Microbial Diseases and Immunity, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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541
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Taguchi F, Ogawa Y, Takeuchi K, Suzuki T, Toyoda K, Shiraishi T, Ichinose Y. A homologue of the 3-oxoacyl-(acyl carrier protein) synthase III gene located in the glycosylation island of Pseudomonas syringae pv. tabaci regulates virulence factors via N-acyl homoserine lactone and fatty acid synthesis. J Bacteriol 2006; 188:8376-84. [PMID: 17028280 PMCID: PMC1698239 DOI: 10.1128/jb.00763-06] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2006] [Accepted: 09/15/2006] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae pv. tabaci 6605 possesses a genetic region involved in flagellin glycosylation. This region is composed of three open reading frames: orf1, orf2, and orf3. Our previous study revealed that orf1 and orf2 encode glycosyltransferases; on the other hand, orf3 has no role in posttranslational modification of flagellin. Although the function of Orf3 remained unclear, an orf3 deletion mutant (Deltaorf3 mutant) had reduced virulence on tobacco plants. Orf3 shows significant homology to a 3-oxoacyl-(acyl carrier protein) synthase III in the fatty acid elongation cycle. The Deltaorf3 mutant had a significantly reduced ability to form acyl homoserine lactones (AHLs), which are quorum-sensing molecules, suggesting that Orf3 is required for AHL synthesis. In comparison with the wild-type strain, swarming motility, biosurfactant production, and tolerance to H2O2 and antibiotics were enhanced in the Deltaorf3 mutant. A scanning electron micrograph of inoculated bacteria on the tobacco leaf surface revealed that there is little extracellular polymeric substance matrix surrounding the cells in the Deltaorf3 mutant. The phenotypes of the Deltaorf3 mutant and an AHL synthesis (DeltapsyI) mutant were similar, although the mutant-specific characteristics were more extreme in the Deltaorf3 mutant. The swarming motility of the Deltaorf3 mutant was greater than that of the DeltapsyI mutant. This was attributed to the synergistic effects of the overproduction of biosurfactants and/or alternative fatty acid metabolism in the Deltaorf3 mutant. Furthermore, the amounts of iron and biosurfactant seem to be involved in biofilm development under quorum-sensing regulation in P. syringae pv. tabaci 6605.
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Affiliation(s)
- Fumiko Taguchi
- The Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka 1-1-1, Okayama 700-8530, Japan
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542
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Shrout JD, Chopp DL, Just CL, Hentzer M, Givskov M, Parsek MR. The impact of quorum sensing and swarming motility on Pseudomonas aeruginosa biofilm formation is nutritionally conditional. Mol Microbiol 2006; 62:1264-77. [PMID: 17059568 DOI: 10.1111/j.1365-2958.2006.05421.x] [Citation(s) in RCA: 382] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of quorum sensing in Pseudomonas aeruginosa biofilm formation is unclear. Some researchers have shown that quorum sensing is important for biofilm development, while others have indicated it has little or no role. In this study, the contribution of quorum sensing to biofilm development was found to depend upon the nutritional environment. Depending upon the carbon source, quorum-sensing mutant strains (lasIrhlI and lasRrhlR) either exhibited a pronounced defect early in biofilm formation or formed biofilms identical to the wild-type strain. Quorum sensing was then shown to exert its nutritionally conditional control of biofilm development through regulation of swarming motility. Examination of pilA and fliM mutant strains further supported the role of swarming motility in biofilm formation. These data led to a model proposing that the prevailing nutritional conditions dictate the contributions of quorum sensing and swarming motility at a key juncture early in biofilm development.
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Affiliation(s)
- Joshua D Shrout
- Department of Microbiology, University of Iowa, Iowa City, IA, USA
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543
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Murray TS, Kazmierczak BI. FlhF is required for swimming and swarming in Pseudomonas aeruginosa. J Bacteriol 2006; 188:6995-7004. [PMID: 16980502 PMCID: PMC1595508 DOI: 10.1128/jb.00790-06] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
FlhF is a signal recognition particle-like protein present in monotrichous bacteria. The loss of FlhF in various bacteria results in decreased transcription of class II, III, or IV flagellar genes, leads to diminished or absent motility, and results in the assembly of flagella at nonpolar locations on the cell surface. In this work, we demonstrate that the loss of FlhF results in defective swimming and swarming motility of Pseudomonas aeruginosa. The FlhF protein localizes to the flagellar pole; in the absence of FlhF, flagellar assembly occurs but is no longer restricted to the pole. DeltaflhF bacteria swim at lower velocities than wild-type bacteria in liquid media and can no longer swarm when assayed under standard swarming conditions (0.5% agar). However, DeltaflhF bacteria regain swarming behavior when plated on 0.3% agar. DeltaflhF organisms show decreased transcription and expression of flagellin (FliC) both in liquid media and on swarming plates compared to wild-type bacteria. However, changes in flagellin expression do not explain the different motility patterns observed for DeltaflhF bacteria. Instead, the aberrant placement of flagella in DeltaflhF bacteria may reduce their ability to move this rod-shaped organism effectively.
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Affiliation(s)
- Thomas S Murray
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT, USA
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544
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Leech AJ, Mattick JS. Effect of site-specific mutations in different phosphotransfer domains of the chemosensory protein ChpA on Pseudomonas aeruginosa motility. J Bacteriol 2006; 188:8479-86. [PMID: 17012390 PMCID: PMC1698234 DOI: 10.1128/jb.00157-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The virulence of Pseudomonas aeruginosa and other surface pathogens involves the coordinate expression of a wide range of virulence determinants, including type IV pili. These surface filaments are important for the colonization of host epithelial tissues and mediate bacterial attachment to, and translocation across, surfaces by a process known as twitching motility. This process is controlled in part by a complex signal transduction system whose central component, ChpA, possesses nine potential sites of phosphorylation, including six histidine-containing phosphotransfer (HPt) domains, one serine-containing phosphotransfer domain, one threonine-containing phosphotransfer domain, and one CheY-like receiver domain. Here, using site-directed mutagenesis, we show that normal twitching motility is entirely dependent on the CheY-like receiver domain and partially dependent on two of the HPt domains. Moreover, under different assay conditions, point mutations in several of the phosphotransfer domains of ChpA give rise to unusual "swarming" phenotypes, possibly reflecting more subtle perturbations in the control of P. aeruginosa motility that are not evident from the conventional twitching stab assay. Together, these results suggest that ChpA plays a central role in the complex regulation of type IV pilus-mediated motility in P. aeruginosa.
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Affiliation(s)
- Andrew J Leech
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
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545
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Daniels R, Reynaert S, Hoekstra H, Verreth C, Janssens J, Braeken K, Fauvart M, Beullens S, Heusdens C, Lambrichts I, De Vos DE, Vanderleyden J, Vermant J, Michiels J. Quorum signal molecules as biosurfactants affecting swarming in Rhizobium etli. Proc Natl Acad Sci U S A 2006; 103:14965-70. [PMID: 16990436 PMCID: PMC1595459 DOI: 10.1073/pnas.0511037103] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Swarming motility is suggested to be a social phenomenon that enables groups of bacteria to coordinately and rapidly move atop solid surfaces. This multicellular behavior, during which the apparently organized bacterial populations are embedded in an extracellular slime layer, has previously been linked with biofilm formation and virulence. Many population density-controlled activities involve the activation of complex signaling pathways using small diffusible molecules, also known as autoinducers. In Gram-negative bacteria, quorum sensing (QS) is achieved primarily by means of N-acylhomoserine lactones (AHLs). Here, we report on a dual function of AHL molecules in controlling swarming behavior of Rhizobium etli, the bacterial symbiotic partner of the common bean plant. The major swarming regulator of R. etli is the cinIR QS system, which is specifically activated in swarming cells by its cognate AHL and other long-chain AHLs. This signaling role of long-chain AHLs is required for high-level expression of the cin and rai QS systems. Besides this signaling function, the long-chain AHLs also have a direct role in surface movement of swarmer cells as these molecules possess significant surface activity and induce liquid flows, known as Marangoni flows, as a result of gradients in surface tension at biologically relevant concentrations. These results point to an as-yet-undisclosed direct role of long-chain AHL molecules as biosurfactants.
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Affiliation(s)
- Ruth Daniels
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Sven Reynaert
- Department of Chemical Engineering, Applied Rheology and Polymer Processing Section, Katholieke Universiteit Leuven, de Croylaan 46, B-3001 Leuven, Belgium
| | - Hans Hoekstra
- Department of Chemical Engineering, Applied Rheology and Polymer Processing Section, Katholieke Universiteit Leuven, de Croylaan 46, B-3001 Leuven, Belgium
| | - Christel Verreth
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Joost Janssens
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
- Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, B-3001 Leuven, Belgium; and
| | - Kristien Braeken
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Maarten Fauvart
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Serge Beullens
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Christophe Heusdens
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Ivo Lambrichts
- Biomedical Research Institute, Hasselt University, Agoralaan, B-3590 Diepenbeek, Belgium
| | - Dirk E. De Vos
- Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, B-3001 Leuven, Belgium; and
| | - Jos Vanderleyden
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
| | - Jan Vermant
- Department of Chemical Engineering, Applied Rheology and Polymer Processing Section, Katholieke Universiteit Leuven, de Croylaan 46, B-3001 Leuven, Belgium
| | - Jan Michiels
- *Department of Microbial and Molecular Systems, Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
- To whom correspondence should be addressed. E-mail:
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546
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Zulianello L, Canard C, Köhler T, Caille D, Lacroix JS, Meda P. Rhamnolipids are virulence factors that promote early infiltration of primary human airway epithelia by Pseudomonas aeruginosa. Infect Immun 2006; 74:3134-47. [PMID: 16714541 PMCID: PMC1479292 DOI: 10.1128/iai.01772-05] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The opportunistic bacterium Pseudomonas aeruginosa causes chronic respiratory infections in cystic fibrosis and immunocompromised individuals. Bacterial adherence to the basolateral domain of the host cells and internalization are thought to participate in P. aeruginosa pathogenicity. However, the mechanism by which the pathogen initially modulates the paracellular permeability of polarized respiratory epithelia remains to be understood. To investigate this mechanism, we have searched for virulence factors secreted by P. aeruginosa that affect the structure of human airway epithelium in the early stages of infection. We have found that only bacterial strains secreting rhamnolipids were efficient in modulating the barrier function of an in vitro-reconstituted human respiratory epithelium, irrespective of their release of elastase and lipopolysaccharide. In contrast to previous reports, we document that P. aeruginosa was not internalized by epithelial cells. We further report that purified rhamnolipids, applied on the surfaces of the epithelia, were sufficient to functionally disrupt the epithelia and to promote the paracellular invasion of rhamnolipid-deficient P. aeruginosa. The mechanism involves the incorporation of rhamnolipids within the host cell membrane, leading to tight-junction alterations. The study provides direct evidence for a hitherto unknown mechanism whereby the junction-dependent barrier of the respiratory epithelium is selectively altered by rhamnolipids.
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Affiliation(s)
- Laurence Zulianello
- Department of Cell Physiology and Metabolism, Medical Center, University of Geneva, 1, rue Michel Servet, Geneva 04 CH1211, Switzerland.
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547
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Miller DJ, Zhang YM, Rock CO, White SW. Structure of RhlG, an Essential β-Ketoacyl Reductase in the Rhamnolipid Biosynthetic Pathway of Pseudomonas aeruginosa. J Biol Chem 2006; 281:18025-32. [PMID: 16624803 DOI: 10.1074/jbc.m601687200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhamnolipids are extracellular biosurfactants and virulence factors secreted by the opportunistic human pathogen Pseudomonas aeruginosa that are required for swarming motility. The rhlG gene is essential for rhamnolipid formation, and the RhlG enzyme is thought to divert fatty acid synthesis intermediates into the rhamnolipid biosynthetic pathway based on its similarity to FabG, the beta-ketoacyl-acyl carrier protein (ACP) reductase of type II fatty acid synthesis. Crystallographic analysis reveals that the overall structures of the RhlG.NADP+ and FabG.NADP+ complexes are indeed similar, but there are key differences related to function. RhlG does not undergo the conformational changes upon NADP(H) binding at the active site that in FabG are the structural basis of negative allostery. Also, the acyl chain-binding pocket of RhlG is narrow and rigid compared with the larger, flexible substrate-binding subdomain in FabG. Finally, RhlG lacks a positively charged/hydrophobic surface feature adjacent to the active site that is found on enzymes like FabG that recognize the ACP of fatty acid synthesis. RhlG catalyzed the NADPH-dependent reduction of beta-ketodecanoyl-ACP to beta-d-hydroxydecanoyl-ACP. However, the enzyme was 2000-fold less active than FabG in carrying out the same reaction. These structural and biochemical studies establish RhlG as a NADPH-dependent beta-ketoacyl reductase of the SDR protein superfamily and further suggest that the ACP of fatty acid synthesis does not carry the substrates for RhlG.
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Affiliation(s)
- Darcie J Miller
- Department of Structural Biology, St. Jude Children's Research Hospital, 332 N. Lauderdale Street, Memphis, TN 38105, USA
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548
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Dubern JF, Lugtenberg BJJ, Bloemberg GV. The ppuI-rsaL-ppuR quorum-sensing system regulates biofilm formation of Pseudomonas putida PCL1445 by controlling biosynthesis of the cyclic lipopeptides putisolvins I and II. J Bacteriol 2006; 188:2898-906. [PMID: 16585751 PMCID: PMC1447005 DOI: 10.1128/jb.188.8.2898-2906.2006] [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] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas putida strain PCL1445 produces two cyclic lipopeptides, putisolvin I and putisolvin II, which possess surface tension-reducing abilities and are able to inhibit biofilm formation and to break down existing biofilms of several Pseudomonas spp., including P. aeruginosa. Putisolvins are secreted in the culture medium during growth at late exponential phase, indicating that production is possibly regulated by quorum sensing. In the present study, we identified a quorum-sensing system in PCL1445 that is composed of ppuI, rsaL, and ppuR and shows very high similarity with gene clusters of P. putida strains IsoF and WCS358. Strains with mutations in ppuI and ppuR showed a severe reduction of putisolvin production. Expression analysis of the putisolvin biosynthetic gene in a ppuI background showed decreased expression, which could be complemented by the addition of synthetic 3-oxo-C(10)-N-acyl homoserine lactone (3-oxo-C(10)-AHL) or 3-oxo-C(12)-AHL to the medium. An rsaL mutant overproduces AHLs, and production of putisolvins is induced early during growth. Analysis of biofilm formation on polyvinylchloride showed that ppuI and ppuR mutants produce a denser biofilm than PCL1445, which correlates with decreased production of putisolvins, whereas an rsaL mutant shows a delay in biofilm production, which correlates with early production of putisolvins. The results demonstrate that quorum-sensing signals induce the production of cyclic lipopeptides putisolvin I and II and consequently control biofilm formation by Pseudomonas putida.
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Affiliation(s)
- Jean-Frédéric Dubern
- Leiden University, Institute of Biology, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands
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549
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An D, Danhorn T, Fuqua C, Parsek MR. Quorum sensing and motility mediate interactions between Pseudomonas aeruginosa and Agrobacterium tumefaciens in biofilm cocultures. Proc Natl Acad Sci U S A 2006; 103:3828-33. [PMID: 16537456 PMCID: PMC1533783 DOI: 10.1073/pnas.0511323103] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the environment, multiple microbial taxa typically coexist as communities, competing for resources and, often, physically associated within biofilms. A dual-species cocultivation model has been developed by using two ubiquitous and well studied microbes Pseudomonas aeruginosa (P.a.) and Agrobacterium tumefaciens (A.t.) as a tractable system to identify molecular mechanisms that underlie multispecies microbial associations. Several factors were found to influence coculture interactions. P.a. had a distinct growth-rate advantage in cocultures, increasing its relative abundance during planktonic and biofilm growth. P.a. also demonstrated a slight quorum-sensing-dependent increase in growth yield in liquid cocultures. P.a. dominated coculture biofilms, "blanketing" or burying immature A.t. microcolonies. P.a. flagellar and type IV pili mutant strains exhibited deficient blanketing and impaired competition in coculture biofilms, whereas, in planktonic coculture, these mutations had no effect on competition. In contrast, A.t. used motility to emigrate from coculture biofilms. In both planktonic and biofilm cocultures, A.t. remained viable for extended periods of time, coexisting with its more numerous competitor. These findings reveal that quorum-sensing-regulated functions and surface motility are important microbial competition factors for P.a. and that the outcome of competition and the relative contribution of different factors to competition are strongly influenced by the environment in which they occur.
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Affiliation(s)
- Dingding An
- *Department of Microbiology, University of Iowa, Iowa City, IA 52242
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208
| | - Thomas Danhorn
- Department of Biology, Indiana University, Bloomington, IN 47405; and
| | - Clay Fuqua
- Department of Biology, Indiana University, Bloomington, IN 47405; and
| | - Matthew R. Parsek
- *Department of Microbiology, University of Iowa, Iowa City, IA 52242
- To whom correspondence should be addressed at:
540 EMRB, Department of Microbiology, The Roy and Lucille Carver College of Medicine, University of Iowa, Iowa City, IA 52242. E-mail:
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550
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Kim W, Surette MG. Coordinated regulation of two independent cell-cell signaling systems and swarmer differentiation in Salmonella enterica serovar Typhimurium. J Bacteriol 2006; 188:431-40. [PMID: 16385032 PMCID: PMC1347318 DOI: 10.1128/jb.188.2.431-440.2006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Almost all members of the genus Salmonella differentiate and migrate on semisolid surfaces in a coordinated population behavior known as swarming. Important virulence determinants are coupled to swarmer differentiation in several other pathogenic organisms, collectively suggesting that conditions that trigger swarming in the laboratory may fortuitously promote the cells to enter a robust physiological state relevant to the host environment. Here, we present evidence that expression of two independent cell-cell signaling systems are also coupled to swarmer differentiation in S. enterica serovar Typhimurium. Expression of both pfs and sdiA genes was up-regulated in the actively migrating swarmers compared to their vegetative counterparts propagated in broth or spread plated on the surface of swim, swarm, and solid media. Accordingly, swarmers produced elevated levels of a universally recognized signaling molecule, autoinducer-2, and exhibited increased sensitivity to N-acyl homoserine lactones (AHLs), signaling molecules that Salmonella does not produce. Expression of the rck operon was concomitantly up-regulated in the swarmers in an SdiA-dependent manner only in the presence of exogenous AHLs. In addition to the previously reported adaptive antibiotic resistance phenotype and global shift in metabolism, this work presents another component of the physiological changes that are specifically associated with swarmer differentiation in serovar Typhimurium and not simply due to growth on a surface.
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Affiliation(s)
- Wook Kim
- Department of Microbiology and Infectious Diseases, University of Calgary, 3330 Hospital Dr. NW, Calgary, Alberta, Canada T2N 4N1
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