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Suppiger A, Schmid N, Aguilar C, Pessi G, Eberl L. Two quorum sensing systems control biofilm formation and virulence in members of the Burkholderia cepacia complex. Virulence 2014; 4:400-9. [PMID: 23799665 PMCID: PMC3714132 DOI: 10.4161/viru.25338] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Burkholderia cepacia complex (Bcc) consists of 17 closely related species that are problematic opportunistic bacterial pathogens for cystic fibrosis patients and immunocompromised individuals. These bacteria are capable of utilizing two different chemical languages: N-acyl homoserine lactones (AHLs) and cis-2-unsaturated fatty acids. Here we summarize the current knowledge of the underlying molecular architectures of these communication systems, showing how they are interlinked and discussing how they regulate overlapping as well as specific sets of genes. A particular focus is laid on the role of these signaling systems in the formation of biofilms, which are believed to be highly important for chronic infections. We review genes that have been implicated in the sessile lifestyle of this group of bacteria. The new emerging role of the intracellular second messenger cyclic dimeric guanosine monophosphate (c-di-GMP) as a downstream regulator of the fatty acid signaling cascade and as a key factor in biofilm formation is also discussed.
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Affiliation(s)
- Angela Suppiger
- Department of Microbiology, University of Zürich, Zürich, Switzerland
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152
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Ionescu M, Baccari C, Da Silva AM, Garcia A, Yokota K, Lindow SE. Diffusible signal factor (DSF) synthase RpfF of Xylella fastidiosa is a multifunction protein also required for response to DSF. J Bacteriol 2013; 195:5273-84. [PMID: 24056101 PMCID: PMC3837960 DOI: 10.1128/jb.00713-13] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 09/13/2013] [Indexed: 11/20/2022] Open
Abstract
Xylella fastidiosa, like related Xanthomonas species, employs an Rpf cell-cell communication system consisting of a diffusible signal factor (DSF) synthase, RpfF, and a DSF sensor, RpfC, to coordinate expression of virulence genes. While phenotypes of a ΔrpfF strain in Xanthomonas campestris could be complemented by its own DSF, the DSF produced by X. fastidiosa (XfDSF) did not restore expression of the XfDSF-dependent genes hxfA and hxfB to a ΔrpfF strain of X. fastidiosa, suggesting that RpfF is involved in XfDSF sensing or XfDSF-dependent signaling. To test this conjecture, rpfC and rpfF of X. campestris were replaced by those of X. fastidiosa, and the contribution of each gene to the induction of a X. campestris DSF-dependent gene was assessed. As in X. fastidiosa, XfDSF-dependent signaling required both X. fastidiosa proteins RpfF and RpfC. RpfF repressed RpfC signaling activity, which in turn was derepressed by XfDSF. A mutated X. fastidiosa RpfF protein with two substitutions of glutamate to alanine in its active site was incapable of XfDSF production yet enabled a response to XfDSF, indicating that XfDSF production and the response to XfDSF are two separate functions in which RpfF is involved. This mutant was also hypervirulent to grape, demonstrating the antivirulence effects of XfDSF itself in X. fastidiosa. The Rpf system of X. fastidiosa is thus a novel example of a quorum-sensing signal synthase that is also involved in the response to the signal molecule that it synthesizes.
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Affiliation(s)
- Michael Ionescu
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
| | - Clelia Baccari
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
| | - Aline Maria Da Silva
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Angelica Garcia
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
| | - Kenji Yokota
- Department of Applied Biology and Chemistry, Tokyo University of Agriculture, Tokyo, Japan
| | - Steven E. Lindow
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
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153
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Abstract
Cell-cell communication, or quorum sensing, is a widespread phenomenon in bacteria that is used to coordinate gene expression among local populations. Its use by bacterial pathogens to regulate genes that promote invasion, defense, and spread has been particularly well documented. With the ongoing emergence of antibiotic-resistant pathogens, there is a current need for development of alternative therapeutic strategies. An antivirulence approach by which quorum sensing is impeded has caught on as a viable means to manipulate bacterial processes, especially pathogenic traits that are harmful to human and animal health and agricultural productivity. The identification and development of chemical compounds and enzymes that facilitate quorum-sensing inhibition (QSI) by targeting signaling molecules, signal biogenesis, or signal detection are reviewed here. Overall, the evidence suggests that QSI therapy may be efficacious against some, but not necessarily all, bacterial pathogens, and several failures and ongoing concerns that may steer future studies in productive directions are discussed. Nevertheless, various QSI successes have rightfully perpetuated excitement surrounding new potential therapies, and this review highlights promising QSI leads in disrupting pathogenesis in both plants and animals.
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154
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Deng Y, Boon C, Chen S, Lim A, Zhang LH. Cis-2-dodecenoic acid signal modulates virulence of Pseudomonas aeruginosa through interference with quorum sensing systems and T3SS. BMC Microbiol 2013; 13:231. [PMID: 24134835 PMCID: PMC4016476 DOI: 10.1186/1471-2180-13-231] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/15/2013] [Indexed: 12/23/2022] Open
Abstract
Background Cis-2-dodecenoic acid (BDSF) is well known for its important functions in intraspecies signaling in Burkholderia cenocepacia. Previous work has also established an important role of BDSF in interspecies and inter-kingdom communications. It was identified that BDSF modulates virulence of Pseudomonas aeruginosa. However, how BDSF interferes with virulence of P. aeruginosa is still not clear. Results We report here that BDSF mediates the cross-talk between B. cenocepacia and P. aeruginosa through interference with quorum sensing (QS) systems and type III secretion system (T3SS) of P. aeruginosa. Bioassay results revealed that exogenous addition of BDSF not only reduced the transcriptional expression of the regulator encoding gene of QS systems, i.e., lasR, pqsR, and rhlR, but also simultaneously decreased the production of QS signals including 3-oxo-C12-HSL, Pseudomonas quinolone signal (PQS) and C4-HSL, consequently resulting in the down-regulation of biofilm formation and virulence factor production of P. aeruginosa. Furthermore, BDSF and some of its derivatives are also capable of inhibiting T3SS of P. aeruginosa at a micromolar level. Treatment with BDSF obviously reduced the virulence of P. aeruginosa in both HeLa cell and zebrafish infection models. Conclusions These results depict that BDSF modulates virulence of P. aeruginosa through interference with QS systems and T3SS.
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Affiliation(s)
- Yinyue Deng
- Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, Singapore, 138673, Singapore.
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155
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Deng Y, Lim A, Wang J, Zhou T, Chen S, Lee J, Dong YH, Zhang LH. Cis-2-dodecenoic acid quorum sensing system modulates N-acyl homoserine lactone production through RpfR and cyclic di-GMP turnover in Burkholderia cenocepacia. BMC Microbiol 2013; 13:148. [PMID: 23815566 PMCID: PMC3703271 DOI: 10.1186/1471-2180-13-148] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 06/27/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Burkholderia cenocepacia employs both N-Acyl homoserine lactone (AHL) and cis-2-dodecenoic acid (BDSF) quorum sensing (QS) systems in regulation of bacterial virulence. It was shown recently that disruption of BDSF synthase RpfFBc caused a reduction of AHL signal production in B. cenocepacia. However, how BDSF system influences AHL system is still not clear. RESULTS We show here that BDSF system controls AHL system through a novel signaling mechanism. Null mutation of either the BDSF synthase, RpfFBc, or the BDSF receptor, RpfR, caused a substantial down-regulation of AHL signal production in B. cenocepacia strain H111. Genetic and biochemical analyses showed that BDSF system controls AHL signal production through the transcriptional regulation of the AHL synthase gene cepI by modulating the intracellular level of second messenger cyclic di-GMP (c-di-GMP). Furthermore, we show that BDSF and AHL systems have a cumulative role in the regulation of various biological functions, including swarming motility, biofilm formation and virulence factor production, and exogenous addition of either BDSF or AHL signal molecules could only partially rescue the changed phenotypes of the double deletion mutant defective in BDSF and AHL signal production. CONCLUSIONS These results, together with our previous findings, thus depict a molecular mechanism with which BDSF regulates AHL signal production and bacterial virulence through modulating the phosphodiesterase activity of its receptor RpfR to influence the intracellular level of c-di-GMP.
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Affiliation(s)
- Yinyue Deng
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos 138673, Singapore
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156
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Ham JH. Intercellular and intracellular signalling systems that globally control the expression of virulence genes in plant pathogenic bacteria. MOLECULAR PLANT PATHOLOGY 2013; 14. [PMID: 23186372 PMCID: PMC6638695 DOI: 10.1111/mpp.12005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Plant pathogenic bacteria utilize complex signalling systems to control the expression of virulence genes at the cellular level and within populations. Quorum sensing (QS), an important intercellular communication mechanism, is mediated by different types of small molecules, including N-acyl homoserine lactones (AHLs), fatty acids and small proteins. AHL-mediated signalling systems dependent on the LuxI and LuxR family proteins play critical roles in the virulence of a wide range of Gram-negative plant pathogenic bacteria belonging to the Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. Xanthomonas spp. and Xylella fastidiosa, members of the Gammaproteobacteria, however, possess QS systems that are mediated by fatty acid-type diffusible signal factors (DSFs). Recent studies have demonstrated that Ax21, a 194-amino-acid protein in Xanthomonas oryzae pv. oryzae, plays dual functions in activating a rice innate immune pathway through binding to the rice XA21 pattern recognition receptor and in regulating bacterial virulence and biofilm formation as a QS signal molecule. In xanthomonads, DSF-mediated QS systems are connected with the signalling pathways mediated by cyclic diguanosine monophosphate (c-di-GMP), which functions as a second messenger for the control of virulence gene expression in these bacterial pathogens.
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Affiliation(s)
- Jong Hyun Ham
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
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157
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Qian G, Liu C, Wu G, Yin F, Zhao Y, Zhou Y, Zhang Y, Song Z, Fan J, Hu B, Liu F. AsnB, regulated by diffusible signal factor and global regulator Clp, is involved in aspartate metabolism, resistance to oxidative stress and virulence in Xanthomonas oryzae pv. oryzicola. MOLECULAR PLANT PATHOLOGY 2013; 14:145-57. [PMID: 23157387 PMCID: PMC6638903 DOI: 10.1111/j.1364-3703.2012.00838.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Xanthomonas oryzae pv. oryzicola (Xoc) causes bacterial leaf streak in rice, which is a destructive disease worldwide. Xoc virulence factors are regulated by diffusible signal factor (DSF) and the global regulator Clp. In this study, we have demonstrated that asnB (XOC_3054), encoding an asparagine synthetase, is a novel virulence-related gene regulated by both DSF and Clp in Xoc. A sequence analysis revealed that AsnB is highly conserved in Xanthomonas. An asnB mutation in Xoc dramatically impaired pathogen virulence and growth rate in host rice, but did not affect the ability to trigger the hypersensitive response in nonhost (plant) tobacco. Compared with the wild-type strain, the asnB deletion mutant was unable to grow in basic MMX (-) medium (a minimal medium without ammonium sulphate as the nitrogen source) with or without 10 tested nitrogen sources, except asparagine. The disruption of asnB impaired pathogen resistance to oxidative stress and reduced the transcriptional expression of oxyR, katA and katG, which encode three important proteins responsible for hydrogen peroxide (H(2)O(2)) sensing and detoxification in Xanthomonas in the presence of H(2)O(2), and nine important known Xoc virulence-related genes in plant cell-mimicking medium. Furthermore, the asnB mutation did not affect extracellular protease activity, extracellular polysaccharide production, motility or chemotaxis. Taken together, our results demonstrate the role of asnB in Xanthomonas for the first time.
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Affiliation(s)
- Guoliang Qian
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
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158
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Pieretti I, Royer M, Barbe V, Carrere S, Koebnik R, Couloux A, Darrasse A, Gouzy J, Jacques MA, Lauber E, Manceau C, Mangenot S, Poussier S, Segurens B, Szurek B, Verdier V, Arlat M, Gabriel DW, Rott P, Cociancich S. Genomic insights into strategies used by Xanthomonas albilineans with its reduced artillery to spread within sugarcane xylem vessels. BMC Genomics 2012; 13:658. [PMID: 23171051 PMCID: PMC3542200 DOI: 10.1186/1471-2164-13-658] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 11/18/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy compared to other species of Xanthomonas. For example, this species produces a potent DNA gyrase inhibitor called albicidin that is largely responsible for inducing disease symptoms; its habitat is limited to xylem; and the species exhibits large variability. A first manuscript on the complete genome sequence of the highly pathogenic X. albilineans strain GPE PC73 focused exclusively on distinctive genomic features shared with Xylella fastidiosa-another xylem-limited Xanthomonadaceae. The present manuscript on the same genome sequence aims to describe all other pathogenicity-related genomic features of X. albilineans, and to compare, using suppression subtractive hybridization (SSH), genomic features of two strains differing in pathogenicity. RESULTS Comparative genomic analyses showed that most of the known pathogenicity factors from other Xanthomonas species are conserved in X. albilineans, with the notable absence of two major determinants of the "artillery" of other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis gene cluster, and the type III secretion system Hrp (hypersensitive response and pathogenicity). Genomic features specific to X. albilineans that may contribute to specific adaptation of this pathogen to sugarcane xylem vessels were also revealed. SSH experiments led to the identification of 20 genes common to three highly pathogenic strains but missing in a less pathogenic strain. These 20 genes, which include four ABC transporter genes, a methyl-accepting chemotaxis protein gene and an oxidoreductase gene, could play a key role in pathogenicity. With the exception of hypothetical proteins revealed by our comparative genomic analyses and SSH experiments, no genes potentially involved in any offensive or counter-defensive mechanism specific to X. albilineans were identified, supposing that X. albilineans has a reduced artillery compared to other pathogenic Xanthomonas species. Particular attention has therefore been given to genomic features specific to X. albilineans making it more capable of evading sugarcane surveillance systems or resisting sugarcane defense systems. CONCLUSIONS This study confirms that X. albilineans is a highly distinctive species within the genus Xanthomonas, and opens new perpectives towards a greater understanding of the pathogenicity of this destructive sugarcane pathogen.
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Affiliation(s)
| | - Monique Royer
- CIRAD, UMR BGPI, F-34398 Montpellier Cedex 5, France
| | - Valérie Barbe
- CEA/DSV/IG/Génoscope, Centre National de Séquençage, F-91057 Evry Cedex France
| | | | - Ralf Koebnik
- IRD, UMR RPB, F-34394 Montpellier Cedex 5, France
| | - Arnaud Couloux
- CEA/DSV/IG/Génoscope, Centre National de Séquençage, F-91057 Evry Cedex France
| | | | - Jérôme Gouzy
- INRA, UMR LIPM, F-31326 Castanet-Tolosan Cedex France
| | | | | | | | - Sophie Mangenot
- CEA/DSV/IG/Génoscope, Centre National de Séquençage, F-91057 Evry Cedex France
| | - Stéphane Poussier
- Université de la Réunion, UMR PVBMT, F-97715 Saint-Denis La Réunion, France
| | - Béatrice Segurens
- CEA/DSV/IG/Génoscope, Centre National de Séquençage, F-91057 Evry Cedex France
| | - Boris Szurek
- IRD, UMR RPB, F-34394 Montpellier Cedex 5, France
| | | | - Matthieu Arlat
- Université Paul Sabatier, UMR LIPM, F-31326 Castanet-Tolosan Cedex France
| | - Dean W Gabriel
- University of Florida, Plant Pathology Department, Gainesville FL 32605 USA
| | - Philippe Rott
- CIRAD, UMR BGPI, F-34398 Montpellier Cedex 5, France
| | - Stéphane Cociancich
- CIRAD, UMR BGPI, F-34398 Montpellier Cedex 5, France
- UMR BGPI, Campus International de Baillarguet, TA A-54/K, F-34398 Montpellier Cedex 5, France
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159
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The AHL- and BDSF-dependent quorum sensing systems control specific and overlapping sets of genes in Burkholderia cenocepacia H111. PLoS One 2012. [PMID: 23185499 PMCID: PMC3502180 DOI: 10.1371/journal.pone.0049966] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Quorum sensing in Burkholderia cenocepacia H111 involves two signalling systems that depend on different signal molecules, namely N-acyl homoserine lactones (AHLs) and the diffusible signal factor cis-2-dodecenoic acid (BDSF). Previous studies have shown that AHLs and BDSF control similar phenotypic traits, including biofilm formation, proteolytic activity and pathogenicity. In this study we mapped the BDSF stimulon by RNA-Seq and shotgun proteomics analysis. We demonstrate that a set of the identified BDSF-regulated genes or proteins are also controlled by AHLs, suggesting that the two regulons partially overlap. The detailed analysis of two mutually regulated operons, one encoding three lectins and the other one encoding the large surface protein BapA and its type I secretion machinery, revealed that both AHLs and BDSF are required for full expression, suggesting that the two signalling systems operate in parallel. In accordance with this, we show that both AHLs and BDSF are required for biofilm formation and protease production.
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160
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Gomes J, Grunau A, Lawrence AK, Eberl L, Gademann K. Bioinspired, releasable quorum sensing modulators. Chem Commun (Camb) 2012; 49:155-7. [PMID: 23169441 DOI: 10.1039/c2cc37287h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate the synthesis and immobilization of natural product hybrids featuring an acyl-homoserine lactone and a nitrodopamine onto biocompatible TiO(2) surfaces through an operationally simple dip-and-rinse procedure. The resulting immobilized hybrids were shown to be powerful quorum sensing (QS) activators in Pseudomonas strains acting by slow release from the surface.
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Affiliation(s)
- José Gomes
- Department of Chemistry, NCCR Chemical Biology, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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161
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Abstract
ABSTRACT Xylella fastidiosa regulates traits important to both virulence of grape as well as colonization of sharpshooter vectors via its production of a fatty acid signal molecule known as DSF whose production is dependent on rpfF. Although X. fastidiosa rpfF mutants exhibit increased virulence to plants, they are unable to be spread from plant to plant by insect vectors. To gain more insight into the traits that contribute to these processes, a whole-genome Agilent DNA microarray for this species was developed and used to determine the RpfF-dependent regulon by transcriptional profiling. In total, 446 protein coding genes whose expression was significantly different between the wild type and an rpfF mutant (false discovery rate < 0.05) were identified when cells were grown in PW liquid medium. Among them, 165 genes were downregulated in the rpfF mutant compared with the wild-type strain whereas 281 genes were over-expressed. RpfF function was required for regulation of 11 regulatory and σ factors, including rpfE, yybA, PD1177, glnB, rpfG, PD0954, PD0199, PD2050, colR, rpoH, and rpoD. In general, RpfF is required for regulation of genes involved in attachment and biofilm formation, enhancing expression of hemagglutinin genes hxfA and hxfB, and suppressing most type IV pili and gum genes. A large number of other RpfF-dependent genes that might contribute to virulence or insect colonization were also identified such as those encoding hemolysin and colicin V, as well as genes with unknown functions.
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Affiliation(s)
- Nian Wang
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA
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162
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Cis-2-dodecenoic acid receptor RpfR links quorum-sensing signal perception with regulation of virulence through cyclic dimeric guanosine monophosphate turnover. Proc Natl Acad Sci U S A 2012; 109:15479-84. [PMID: 22949660 DOI: 10.1073/pnas.1205037109] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many bacterial pathogens produce diffusible signal factor (DSF)-type quorum sensing (QS) signals in modulation of virulence and biofilm formation. Previous work on Xanthomonas campestris showed that the RpfC/RpfG two-component system is involved in sensing and responding to DSF signals, but little is known in other microorganisms. Here we show that in Burkholderia cenocepacia the DSF-family signal cis-2-dodecenoic acid (BDSF) negatively controls the intracellular cyclic dimeric guanosine monophosphate (c-di-GMP) level through a receptor protein RpfR, which contains Per/Arnt/Sim (PAS)-GGDEF-EAL domains. RpfR regulates the same phenotypes as BDSF including swarming motility, biofilm formation, and virulence. In addition, the BDSF(-) mutant phenotypes could be rescued by in trans expression of RpfR, or its EAL domain that functions as a c-di-GMP phosphodiesterase. BDSF is shown to bind to the PAS domain of RpfR with high affinity and stimulates its phosphodiesterase activity through induction of allosteric conformational changes. Our work presents a unique and widely conserved DSF-family signal receptor that directly links the signal perception to c-di-GMP turnover in regulation of bacterial physiology.
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163
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Qian G, Zhang Y, Zhou Y, Liu C, Zhao Y, Song Z, Fan J, Hu B, Liu F. epv, Encoding a hypothetical protein, is regulated by DSF-mediating quorum sensing as well as global regulator Clp and is required for optimal virulence in Xanthomonas oryzae pv. oryzicola. PHYTOPATHOLOGY 2012; 102:841-7. [PMID: 22881870 DOI: 10.1094/phyto-02-12-0020-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Xanthomonas oryzae pv. oryzicola causes bacterial leaf streak in rice, a destructive disease worldwide. In this study, six putative hypothetical secreted proteins, which were absent in X. oryzae pv. oryzae, were detected from X. oryzae pv. oryzicola strain BLS256. Disruption-based mutagenesis study revealed that one of them, Xoc_15235, named as extracellular polysaccharide and virulence-related gene (epv), was required for the optimal virulence in host rice but not for the induction of a hypersensitive reaction in nonhost tobacco. Sequence analysis revealed that epv was highly conserved in Xanthomonas spp. (except X. oryzae pv. oryzae). In-frame deletion of epv in X. oryzae pv. oryzicola dramatically impaired pathogen virulence and extracellular polysaccharide (EPS) production, one of the important known virulence-associated functions in Xanthomonas spp. Quantitative real-time reverse-transcription polymerase chain reaction showed that expression of both gumB (a gene encoding exopolysaccharide xanthan biosynthesis export protein) and a known virulence-related gene, pgk (encoding phosphoglycerate kinase), were obviously reduced in the epv-deletion mutant compared with the wild-type strain Rs105. In addition, we observed that epv was positively regulated by both diffusible signal factor and global regulator Clp in X. oryzae pv. oryzicola. Taken together, the novel roles and genetics of epv of X. oryzae pv. oryzicola in the EPS production and virulence were investigated for the first time.
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Affiliation(s)
- Guoliang Qian
- College of Plant Protection and Key Laboratory of Integrated Management of Corp Diseases and Pests, Ministry of Education, Nanjing Agricultural University, China
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164
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Rai R, Ranjan M, Pradhan BB, Chatterjee S. Atypical regulation of virulence-associated functions by a diffusible signal factor in Xanthomonas oryzae pv. oryzae. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:789-801. [PMID: 22352717 DOI: 10.1094/mpmi-11-11-0285-r] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, a secreted fatty acid signaling molecule known as diffusible signal factor (DSF) is required for virulence and growth on low-iron medium. To identify other virulence-associated traits that are regulated by DSF in this pathogen, we have performed microarray analysis of transcriptional changes between the wild type and DSF-deficient mutants of X. oryzae pv. oryzae. Expression of genes that encode secreted hydrolytic enzymes, motility, and chemotaxis functions are negatively regulated by DSF while functions involved in adhesion and biofilm formation are positively regulated. Enzymatic assays for hydrolytic enzymes as well as assays for chemotaxis, motility, attachment, and biofilm formation corroborate these findings. These results demonstrate that, in X. oryzae pv. oryzae, DSF-mediated cell-to-cell signaling coordinates transition from solitary to biofilm lifestyle by promoting expression of attachment functions and negatively regulating expression of motility functions. This is in contrast to X. campestris pv. campestris, a pathogen of crucifers, wherein the DSF system positively regulates motility functions and negatively regulates biofilm formation. These results indicate that virulence-associated functions can be regulated in a completely contrasting fashion by the same signaling system in very closely related bacteria.
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Affiliation(s)
- Rikky Rai
- Centre for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad 500001, India
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165
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Almeida RPP, Killiny N, Newman KL, Chatterjee S, Ionescu M, Lindow SE. Contribution of rpfB to cell-to-cell signal synthesis, virulence, and vector transmission of Xylella fastidiosa. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:453-62. [PMID: 22204646 DOI: 10.1094/mpmi-03-11-0074] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In Xylella fastidiosa the fatty acid signal molecule diffusible signaling factor (DSF) is produced and sensed by components of the regulation of pathogenicity factors (rpf) cluster; lack of DSF production in RpfF mutants results in a non-vector-transmissible phenotype yet cells are hypervirulent to grape. rpfB has not been characterized in Xylella fastidiosa, although its homolog has been suggested to be required for DSF synthesis in Xanthomonas campestris pv. campestris. We show that RpfB is involved in DSF processing in both Xylella fastidiosa and Xanthomonas campestris, affecting the profile of DSF-like fatty acids observed in thin-layer chromatography. Although three fatty acids whose production is dependent on RpfF were detected in Xylella fastidiosa and Xanthomonas campestris wild-type strains, their respective rpfB mutants accumulated primarily one chemical species. Although no quantifiable effect of rpfB on plant colonization by Xylella fastidiosa was found, insect colonization and transmission was reduced. Thus, RpfB apparently is involved in DSF processing, and like Xanthomonas campestris, Xylella fastidiosa also produces multiple DSF molecules. It is possible that Xylella fastidiosa coordinates host vector and plant colonization by varying the proportions of different forms of DSF signals via RpfB.
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Affiliation(s)
- Rodrigo P P Almeida
- Department of Environmental Science, Policy, and Management, University of California, Berkeley 94720, USA.
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166
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Clevenger KD, Fast W. "Clicking" on the lights to reveal bacterial social networking. Chembiochem 2012; 13:508-10. [PMID: 22262670 DOI: 10.1002/cbic.201100767] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Indexed: 01/31/2023]
Abstract
"No man is an island." With apologies to John Donne, the same could be said for a bacterium. The discovery of bacterial quorum sensing and its relevance to microbial ecology and pathogenesis have fueled the increasing scrutiny of the molecular mechanisms responsible for the apparent group behavior of microbes. A number of chemically diverse small molecules act as diffusible signaling molecules that regulate gene expression in a population-dependent manner. Some of these signals, such as the N-acyl-L-homoserine lactones, are produced and sensed by others in the same or closely related species, and other chemical classes of signals are used more broadly for interspecies and even interkingdom communication. As a field, the study of these microbial social networks has been termed "sociomicrobiology".
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Affiliation(s)
- Kenneth D Clevenger
- Department of Chem and Biochem, University of Texas, Austin, Austin, TX 78712, USA
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167
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Tiaden A, Hilbi H. α-Hydroxyketone synthesis and sensing by Legionella and Vibrio. SENSORS 2012; 12:2899-919. [PMID: 22736983 PMCID: PMC3376566 DOI: 10.3390/s120302899] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 02/23/2012] [Accepted: 02/23/2012] [Indexed: 01/09/2023]
Abstract
Bacteria synthesize and sense low molecular weight signaling molecules, termed autoinducers, to measure their population density and community complexity. One class of autoinducers, the α-hydroxyketones (AHKs), is produced and detected by the water-borne opportunistic pathogens Legionella pneumophila and Vibrio cholerae, which cause Legionnaires’ disease and cholera, respectively. The “Legionella quorum sensing” (lqs) or “cholera quorum sensing” (cqs) genes encode enzymes that produce and sense the AHK molecules “Legionella autoinducer-1” (LAI-1; 3-hydroxypentadecane-4-one) or cholera autoinducer-1 (CAI-1; 3-hydroxytridecane-4-one). AHK signaling regulates the virulence of L. pneumophila and V. cholerae, pathogen-host cell interactions, formation of biofilms or extracellular filaments, expression of a genomic “fitness island” and competence. Here, we outline the processes, wherein AHK signaling plays a role, and review recent insights into the function of proteins encoded by the lqs and cqs gene clusters. To this end, we will focus on the autoinducer synthases catalysing the biosynthesis of AHKs, on the cognate trans-membrane sensor kinases detecting the signals, and on components of the down-stream phosphorelay cascade that promote the transmission and integration of signaling events regulating gene expression.
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Affiliation(s)
- André Tiaden
- Competence Center for Applied Biotechnology and Molecular Medicine, University Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland; E-Mail:
| | - Hubert Hilbi
- Max von Pettenkofer Institute, Ludwig-Maximilians University Munich, Pettenkoferstrasse 9a, 80336 Munich, Germany
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-89-5160-5264; Fax: +49-89-5160-5223
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168
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Bandara HMHN, Lam OLT, Jin LJ, Samaranayake L. Microbial chemical signaling: a current perspective. Crit Rev Microbiol 2012; 38:217-49. [PMID: 22300377 DOI: 10.3109/1040841x.2011.652065] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Communication among microorganisms is mediated through quorum sensing. The latter is defined as cell-density linked, coordinated gene expression in microbial populations as a response to threshold signal concentrations followed by induction of a synchronized population response. This phenomenon is used by a variety of microbes to optimize their survival in a constantly challenging, dynamic milieu, by correlating individual cellular functions to community-based requirements. The synthesis, secretion, and perception of quorum-sensing molecules and their target response play a pivotal role in quorum sensing and are tightly controlled by complex, multilayered and interconnected signal transduction pathways that regulate diverse cellular functions. Quorum sensing exemplifies interactive social behavior innate to the microbial world that controls features such as, virulence, biofilm maturation, antibiotic resistance, swarming motility, and conjugal plasmid transfer. Over the past two decades, studies have been performed to rationalize bacterial cell-to-cell communication mediated by structurally and functionally diverse small molecules. This review describes the theoretical aspects of cellular and quorum-sensing mechanisms that affect microbial physiology and pathobiology.
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Affiliation(s)
- H M H N Bandara
- Oral Biosciences, Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong
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169
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Bi H, Christensen QH, Feng Y, Wang H, Cronan JE. The Burkholderia cenocepacia BDSF quorum sensing fatty acid is synthesized by a bifunctional crotonase homologue having both dehydratase and thioesterase activities. Mol Microbiol 2012; 83:840-55. [PMID: 22221091 DOI: 10.1111/j.1365-2958.2012.07968.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Signal molecules of the diffusible signal factor (DSF) family have been shown recently to be involved in regulation of pathogenesis and biofilm formation in diverse Gram-negative bacteria. DSF signals are reported to be active not only on their cognate bacteria, but also on unrelated bacteria and the pathogenic yeast, Candida albicans. DSFs are monounsaturated fatty acids of medium chain length containing an unusual cis-2 double bond. Although genetic analyses had identified genes involved in DSF synthesis, the pathway of DSF synthesis was unknown. The DSF of the important human pathogen Burkholderia cenocepacia (called BDSF) is cis-2-dodecenoic acid. We report that BDSF is synthesized from a fatty acid synthetic intermediate, the acyl carrier protein (ACP) thioester of 3-hydroxydodecanoic acid. This intermediate is intercepted by protein Bcam0581 and converted to cis-2-dodecenoyl-ACP. Bcam0581 is annotated as a homologue of crotonase, the first enzyme of the fatty acid degradation pathway. We demonstrated Bcam0581to be a bifunctional protein that not only catalysed dehydration of 3-hydroxydodecanoyl-ACP to cis-2-dodecenoyl-ACP, but also cleaved the thioester bond to give the free acid. Both activities required the same set of active-site residues. Although dehydratase and thioesterase activities are known activities of the crotonase superfamily, Bcam0581 is the first protein shown to have both activities.
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Affiliation(s)
- Hongkai Bi
- Departments of Microbiology Biochemistry, B103 Chemical and Life Sciences Laboratory, University of Illinois, 601 S. Goodwin Ave, Urbana, IL 61801, USA
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170
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Twomey KB, O'Connell OJ, McCarthy Y, Dow JM, O'Toole GA, Plant BJ, Ryan RP. Bacterial cis-2-unsaturated fatty acids found in the cystic fibrosis airway modulate virulence and persistence of Pseudomonas aeruginosa. ISME JOURNAL 2011; 6:939-50. [PMID: 22134647 DOI: 10.1038/ismej.2011.167] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
There is an increasing appreciation of the polymicrobial nature of many bacterial infections such as those associated with cystic fibrosis (CF) and of the potentially important role for interspecies interactions in influencing both bacterial virulence and response to therapy. Patients with CF are often co-infected with Pseudomonas aeruginosa and other pathogens including Burkholderia cenocepacia and Stenotrophomonas maltophilia. These latter bacteria produce signal molecules of the diffusible signal factor (DSF) family, which are cis-2-unsaturated fatty acids. We have previously shown by in vitro studies that DSF from S. maltophilia leads to altered biofilm formation and increased resistance to antibiotics by P. aeruginosa; these responses of P. aeruginosa require the sensor kinase PA1396. Here we show that DSF signals are present in sputum taken from patients with CF. Presence of these DSF signals was correlated with patient colonization by S. maltophilia and/or B. cenocepacia. Analysis of 50 clinical isolates of P. aeruginosa showed that each responded to the presence of synthetic DSF by increased antibiotic resistance and these strains demonstrated little sequence variation in the PA1396 gene. In animal experiments using CF transmembrane conductance regulator knockout mice, the presence of DSF promoted P. aeruginosa persistence. Furthermore, antibiotic resistance of P. aeruginosa biofilms grown on human airway epithelial cells was enhanced in the presence of DSF. Taken together, these data provide substantial evidence that interspecies DSF-mediated bacterial interactions occur in the CF lung and may influence the efficacy of antibiotic treatment, particularly for chronic infections involving persistence of bacteria.
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Affiliation(s)
- Kate B Twomey
- BIOMERIT Research Centre, Department of Microbiology, Biosciences Institute, University College Cork, Cork, Ireland
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171
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Should we stay or should we go: mechanisms and ecological consequences for biofilm dispersal. Nat Rev Microbiol 2011; 10:39-50. [PMID: 22120588 DOI: 10.1038/nrmicro2695] [Citation(s) in RCA: 504] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In most environments, bacteria reside primarily in biofilms, which are social consortia of cells that are embedded in an extracellular matrix and undergo developmental programmes resulting in a predictable biofilm 'life cycle'. Recent research on many different bacterial species has now shown that the final stage in this life cycle includes the production and release of differentiated dispersal cells. The formation of these cells and their eventual dispersal is initiated through diverse and remarkably sophisticated mechanisms, suggesting that there are strong evolutionary pressures for dispersal from an otherwise largely sessile biofilm. The evolutionary aspect of biofilm dispersal is now being explored through the integration of molecular microbiology with eukaryotic ecological and evolutionary theory, which provides a broad conceptual framework for the diversity of specific mechanisms underlying biofilm dispersal. Here, we review recent progress in this emerging field and suggest that the merging of detailed molecular mechanisms with ecological theory will significantly advance our understanding of biofilm biology and ecology.
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172
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Fast W, Tipton PA. The enzymes of bacterial census and censorship. Trends Biochem Sci 2011; 37:7-14. [PMID: 22099187 DOI: 10.1016/j.tibs.2011.10.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 10/04/2011] [Accepted: 10/06/2011] [Indexed: 10/15/2022]
Abstract
N-Acyl-L-homoserine lactones (AHLs) are a major class of quorum-sensing signals used by Gram-negative bacteria to regulate gene expression in a population-dependent manner, thereby enabling group behavior. Enzymes capable of generating and catabolizing AHL signals are of significant interest for the study of microbial ecology and quorum-sensing pathways, for understanding the systems that bacteria have evolved to interact with small-molecule signals, and for their possible use in therapeutic and industrial applications. The recent structural and functional studies reviewed here provide a detailed insight into the chemistry and enzymology of bacterial communication.
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Affiliation(s)
- Walter Fast
- Division of Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, TX 78712, USA.
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173
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Winans SC. A new family of quorum sensing pheromones synthesized using S-adenosylmethionine and Acyl-CoAs. Mol Microbiol 2011; 79:1403-6. [PMID: 21388458 DOI: 10.1111/j.1365-2958.2011.07551.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
It is now widely accepted that populations of bacterial cells often co-ordinate their behaviour via diffusible chemical signals. Many different signals have been documented, but they fall into a relatively small number of families. One such signal, CAI-1, from Vibrio cholerae consists of a substituted 13-carbon alkane. In this issue, Bassler and colleagues provide evidence that CAI-1 exemplifies an entirely new class of pheromones. They also show that one species of Vibrio synthesizes and detects just one such pheromone, while another species synthesizes and detects several. Bioinformatics and data from another group indicate that this new class of signals may be widespread among beta- and gamma-proteobacteria.
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Affiliation(s)
- Stephen C Winans
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA.
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