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Torres M, Jiquel A, Jeanne E, Naquin D, Dessaux Y, Faure D. Agrobacterium tumefaciens fitness genes involved in the colonization of plant tumors and roots. THE NEW PHYTOLOGIST 2022; 233:905-918. [PMID: 34655498 DOI: 10.1111/nph.17810] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/13/2021] [Indexed: 06/13/2023]
Abstract
Agrobacterium tumefaciens colonizes the galls (plant tumors) it causes, and the roots of host and nonhost plants. Transposon-sequencing (Tn-Seq) was used to discover A.tumefaciens genes involved in reproductive success (fitness genes) on Solanum lycopersicum and Populus trichocarpa tumors and S.lycopersicum and Zea mays roots. The identified fitness genes represent 3-8% of A. tumefaciens genes and contribute to carbon and nitrogen metabolism, synthesis and repair of DNA, RNA and proteins and envelope-associated functions. Competition assays between 12 knockout mutants and wild-type confirmed the involvement of 10 genes (trpB, hisH, metH, cobN, ntrB, trxA, nrdJ, kamA, exoQ, wbbL) in A.tumefaciens fitness under both tumor and root conditions. The remaining two genes (fecA, noxA) were important in tumors only. None of these mutants was nonpathogenic, but four (hisH, trpB, exoQ, ntrB) exhibited impaired virulence. Finally, we used this knowledge to search for chemical and biocontrol treatments that target some of the identified fitness pathways and report reduced tumorigenesis and impaired establishment of A.tumefaciens on tomato roots using tannic acid or Pseudomonas protegens, which affect iron assimilation. This work revealed A.tumefaciens pathways that contribute to its competitive survival in plants and highlights a strategy to identify plant protection approaches against this pathogen.
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Affiliation(s)
- Marta Torres
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91190, France
| | - Audren Jiquel
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91190, France
| | - Etienne Jeanne
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91190, France
| | - Delphine Naquin
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91190, France
| | - Yves Dessaux
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91190, France
| | - Denis Faure
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91190, France
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Lang C, Smith LS, Haney CH, Long SR. Characterization of Novel Plant Symbiosis Mutants Using a New Multiple Gene-Expression Reporter Sinorhizobium meliloti Strain. FRONTIERS IN PLANT SCIENCE 2018; 9:76. [PMID: 29467773 PMCID: PMC5808326 DOI: 10.3389/fpls.2018.00076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/15/2018] [Indexed: 06/08/2023]
Abstract
The formation of nitrogen fixing root nodules by Medicago truncatula and Sinorhizobium meliloti requires communication between both organisms and coordinated differentiation of plant and bacterial cells. After an initial signal exchange, the bacteria invade the tissue of the growing nodule via plant-derived tubular structures, called infection threads. The bacteria are released from the infection threads into invasion-competent plant cells, where they differentiate into nitrogen-fixing bacteroids. Both organisms undergo dramatic transcriptional, metabolic and morphological changes during nodule development. To identify plant processes that are essential for the formation of nitrogen fixing nodules after nodule development has been initiated, large scale mutageneses have been conducted to discover underlying plant symbiosis genes. Such screens yield numerous uncharacterized plant lines with nitrogen fixation deficient nodules. In this study, we report construction of a S. meliloti strain carrying four distinct reporter constructs to reveal stages of root nodule development. The strain contains a constitutively expressed lacZ reporter construct; a PexoY-mTFP fusion that is expressed in infection threads but not in differentiated bacteroids; a PbacA-mcherry construct that is expressed in infection threads and during bacteroid differentiation; and a PnifH-uidA construct that is expressed during nitrogen fixation. We used this strain together with fluorescence microscopy to study nodule development over time in wild type nodules and to characterize eight plant mutants from a fast neutron bombardment screen. Based on the signal intensity and the localization patterns of the reporter genes, we grouped mutants with similar phenotypes and placed them in a developmental context.
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Affiliation(s)
| | | | | | - Sharon R. Long
- Gilbert Lab, Department of Biology, Stanford University, Stanford, CA, United States
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Baglivo I, Pirone L, Pedone EM, Pitzer JE, Muscariello L, Marino MM, Malgieri G, Freschi A, Chambery A, Roop Ii RM, Pedone PV. Ml proteins from Mesorhizobium loti and MucR from Brucella abortus: an AT-rich core DNA-target site and oligomerization ability. Sci Rep 2017; 7:15805. [PMID: 29150637 PMCID: PMC5693944 DOI: 10.1038/s41598-017-16127-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 11/07/2017] [Indexed: 11/09/2022] Open
Abstract
Mesorhizobium loti contains ten genes coding for proteins sharing high amino acid sequence identity with members of the Ros/MucR transcription factor family. Five of these Ros/MucR family members from Mesorhizobium loti (Ml proteins) have been recently structurally and functionally characterized demonstrating that Ml proteins are DNA-binding proteins. However, the DNA-binding studies were performed using the Ros DNA-binding site with the Ml proteins. Currently, there is no evidence as to when the Ml proteins are expressed during the Mesorhizobium lo ti life cycle as well as no information concerning their natural DNA-binding site. In this study, we examine the ml genes expression profile in Mesorhizobium loti and show that ml1, ml2, ml3 and ml5 are expressed during planktonic growth and in biofilms. DNA-binding experiments show that the Ml proteins studied bind a conserved AT-rich site in the promoter region of the exoY gene from Mesorhizobium loti and that the proteins make important contacts with the minor groove of DNA. Moreover, we demonstrate that the Ml proteins studied form higher-order oligomers through their N-terminal region and that the same AT-rich site is recognized by MucR from Brucella abortus using a similar mechanism involving contacts with the minor groove of DNA and oligomerization.
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Affiliation(s)
- Ilaria Baglivo
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy.
| | - Luciano Pirone
- Institute of Biostructures and Bioimaging, C.N.R., Naples, 80134, Italy
| | | | - Joshua Edison Pitzer
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Lidia Muscariello
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy
| | - Maria Michela Marino
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy
| | - Gaetano Malgieri
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy
| | - Andrea Freschi
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy
| | - Angela Chambery
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy
| | - Roy-Martin Roop Ii
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Paolo Vincenzo Pedone
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, 81100, Italy.
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Wu D, Li A, Ma F, Yang J, Xie Y. Genetic control and regulatory mechanisms of succinoglycan and curdlan biosynthesis in genus Agrobacterium. Appl Microbiol Biotechnol 2016; 100:6183-6192. [DOI: 10.1007/s00253-016-7650-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 05/18/2016] [Accepted: 05/21/2016] [Indexed: 12/15/2022]
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The Sinorhizobium meliloti SyrM regulon: effects on global gene expression are mediated by syrA and nodD3. J Bacteriol 2015; 197:1792-806. [PMID: 25777671 DOI: 10.1128/jb.02626-14] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 03/06/2015] [Indexed: 01/27/2023] Open
Abstract
UNLABELLED In Sinorhizobium meliloti, three NodD transcriptional regulators activate bacterial nodulation (nod) gene expression. NodD1 and NodD2 require plant compounds to activate nod genes. The NodD3 protein does not require exogenous compounds to activate nod gene expression; instead, another transcriptional regulator, SyrM, activates nodD3 expression. In addition, NodD3 can activate syrM expression. SyrM also activates expression of another gene, syrA, which when overexpressed causes a dramatic increase in exopolysaccharide production. In a previous study, we identified more than 200 genes with altered expression in a strain overexpressing nodD3. In this work, we define the transcriptomes of strains overexpressing syrM or syrA. The syrM, nodD3, and syrA overexpression transcriptomes share similar gene expression changes; analyses imply that nodD3 and syrA are the only targets directly activated by SyrM. We propose that most of the gene expression changes observed when nodD3 is overexpressed are due to NodD3 activation of syrM expression, which in turn stimulates SyrM activation of syrA expression. The subsequent increase in SyrA abundance results in broad changes in gene expression, most likely mediated by the ChvI-ExoS-ExoR regulatory circuit. IMPORTANCE Symbioses with bacteria are prevalent across the animal and plant kingdoms. Our system of study, the rhizobium-legume symbiosis (Sinorhizobium meliloti and Medicago spp.), involves specific host-microbe signaling, differentiation in both partners, and metabolic exchange of bacterial fixed nitrogen for host photosynthate. During this complex developmental process, both bacteria and plants undergo profound changes in gene expression. The S. meliloti SyrM-NodD3-SyrA and ChvI-ExoS-ExoR regulatory circuits affect gene expression and are important for optimal symbiosis. In this study, we defined the transcriptomes of S. meliloti overexpressing SyrM or SyrA. In addition to identifying new targets of the SyrM-NodD3-SyrA regulatory circuit, our work further suggests how it is linked to the ChvI-ExoS-ExoR regulatory circuit.
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Yurgel SN, Rice J, Kahn ML. Transcriptome analysis of the role of GlnD/GlnBK in nitrogen stress adaptation by Sinorhizobium meliloti Rm1021. PLoS One 2013; 8:e58028. [PMID: 23516427 PMCID: PMC3596328 DOI: 10.1371/journal.pone.0058028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 01/30/2013] [Indexed: 11/19/2022] Open
Abstract
Transcriptional changes in the nitrogen stress response (NSR) of wild type S. meliloti Rm1021, and isogenic strains missing both PII proteins, GlnB and GlnK, or carrying a ΔglnD-sm2 mutation were analyzed using whole-genome microarrays. This approach allowed us to identify a number of new genes involved in the NSR and showed that the response of these bacteria to nitrogen stress overlaps with other stress responses, including induction of the fixK2 transcriptional activator and genes that are part of the phosphate stress response. Our data also show that GlnD and GlnBK proteins may regulate many genes that are not part of the NSR. Analysis of transcriptome profiles of the Rm1021 ΔglnD-sm2 strain allowed us to identify several genes that appear to be regulated by GlnD without the participation of the PII proteins.
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Affiliation(s)
- Svetlana N Yurgel
- Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA.
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Dorken G, Ferguson GP, French CE, Poon WCK. Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide. J R Soc Interface 2012; 9:3490-502. [PMID: 22896568 DOI: 10.1098/rsif.2012.0498] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In bacteria, the production of exopolysaccharides--polysaccharides secreted by the cells into their growth medium--is integral to the formation of aggregates and biofilms. These exopolysaccharides often form part of a matrix that holds the cells together. Investigating the bacterium Sinorhizobium meliloti, we found that a mutant that overproduces the exopolysaccharide succinoglycan showed enhanced aggregation, resulting in phase separation of the cultures. However, the aggregates did not appear to be covered in polysaccharides. Succinoglycan purified from cultures was applied to different concentrations of cells, and observation of the phase behaviour showed that the limiting polymer concentration for aggregation and phase separation to occur decreased with increasing cell concentration, suggesting a 'crowding mechanism' was occurring. We suggest that, as found in colloidal dispersions, the presence of a non-adsorbing polymer in the form of the exopolysaccharide succinoglycan drives aggregation of S. meliloti by depletion attraction. This force leads to self-organization of the bacteria into small clusters of laterally aligned cells, and, furthermore, leads to aggregates clustering into biofilm-like structures on a surface.
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Affiliation(s)
- Gary Dorken
- Institute of Structural and Molecular Biology, School of Biological Sciences, University of Edinburgh, Darwin Building, Mayfield Road, Edinburgh EH9 3JR, UK
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Gao M, Coggin A, Yagnik K, Teplitski M. Role of specific quorum-sensing signals in the regulation of exopolysaccharide II production within Sinorhizobium meliloti spreading colonies. PLoS One 2012; 7:e42611. [PMID: 22912712 PMCID: PMC3418255 DOI: 10.1371/journal.pone.0042611] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 07/10/2012] [Indexed: 01/21/2023] Open
Abstract
Background Quorum sensing (QS) in Sinorhizobium meliloti involves at least half a dozen different N-acyl homoserine lactone (AHL) signals. These signals are produced by SinI, the sole AHL synthase in S. meliloti Rm8530. The sinI gene is regulated by two LuxR-type transcriptional regulators, SinR and ExpR. Mutations in sinI, sinR and expR abolish the production of exopolysaccharide II (EPS II). Methodology/Principal Findings This study investigated a new type of coordinated surface spreading of Rm8530 that can be categorized as swarming. Motility assays on semi-solid surfaces revealed that both flagella and EPS II are required for this type of motility. The production of EPS II depends on AHLs produced by SinI. Of these AHLs, only C16:1- and 3-oxo-C16:1-homoserine lactones (HSLs) stimulated swarming in an ExpR-dependent manner. These two AHLs induced the strongest response in the wggR reporter fusions. WggR is a positive regulator of the EPS II biosynthesis gene expression. The levels of the wggR activation correlated with the extent of swarming. Furthermore, swarming of S. meliloti required the presence of the high molecular weight (HMW) fraction of EPS II. Within swarming colonies, a recombinase-based RIVET reporter in the wggR gene was resolved in 30% of the cells, indicating an enhanced regulation of EPS II production in the subpopulation of cells, which was sufficient to support swarming of the entire colony. Conclusions/Significance Swarming behavior of S. meliloti Rm8530 on semi-solid surfaces is found to be dependent on the functional QS regulatory cascades. Even though multiple AHL signals are produced by the bacterium, only two AHLs species, C16:1- and 3-oxo-C16:1-HSLs, affected swarming by up-regulating the expression of wggR. While EPS II is produced by Rm8530 as high and low molecular weight fractions, only the HMW EPS II facilitated initial stages of swarming, thus, suggesting a function for this polymer.
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Affiliation(s)
- Mengsheng Gao
- Soil and Water Science Department, University of Florida/Institute of Food and Agricultural Sciences, Gainesville, Florida, United States of America
- * E-mail:
| | | | - Kruti Yagnik
- Soil and Water Science Department, University of Florida/Institute of Food and Agricultural Sciences, Gainesville, Florida, United States of America
| | - Max Teplitski
- Soil and Water Science Department, University of Florida/Institute of Food and Agricultural Sciences, Gainesville, Florida, United States of America
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ExpR is not required for swarming but promotes sliding in Sinorhizobium meliloti. J Bacteriol 2012; 194:2027-35. [PMID: 22328673 DOI: 10.1128/jb.06524-11] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Swarming is a mode of translocation dependent on flagellar activity that allows bacteria to move rapidly across surfaces. In several bacteria, swarming is a phenotype regulated by quorum sensing. It has been reported that the swarming ability of the soil bacterium Sinorhizobium meliloti Rm2011 requires a functional ExpR/Sin quorum-sensing system. However, our previous published results demonstrate that strains Rm1021 and Rm2011, both known to have a disrupted copy of expR, are able to swarm on semisolid minimal medium. In order to clarify these contradictory results, the role played by the LuxR-type regulator ExpR has been reexamined. Results obtained in this work revealed that S. meliloti can move over semisolid surfaces using at least two different types of motility. One type is flagellum-independent surface spreading or sliding, which is positively influenced by a functional expR gene mainly through the production of exopolysaccharide II (EPS II). To a lesser extent, EPS II-deficient strains can also slide on surfaces by a mechanism that is at least dependent on the siderophore rhizobactin 1021. The second type of surface translocation shown by S. meliloti is swarming, which is greatly dependent on flagella and rhizobactin 1021 but does not require ExpR. We have extended our study to demonstrate that the production of normal amounts of succinoglycan (EPS I) does not play a relevant role in surface translocation but that its overproduction facilitates both swarming and sliding motilities.
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Janczarek M. Environmental signals and regulatory pathways that influence exopolysaccharide production in rhizobia. Int J Mol Sci 2011; 12:7898-933. [PMID: 22174640 PMCID: PMC3233446 DOI: 10.3390/ijms12117898] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 11/04/2011] [Accepted: 11/07/2011] [Indexed: 11/16/2022] Open
Abstract
Rhizobia are Gram-negative bacteria that can exist either as free-living bacteria or as nitrogen-fixing symbionts inside root nodules of leguminous plants. The composition of the rhizobial outer surface, containing a variety of polysaccharides, plays a significant role in the adaptation of these bacteria in both habitats. Among rhizobial polymers, exopolysaccharide (EPS) is indispensable for the invasion of a great majority of host plants which form indeterminate-type nodules. Various functions are ascribed to this heteropolymer, including protection against environmental stress and host defense, attachment to abiotic and biotic surfaces, and in signaling. The synthesis of EPS in rhizobia is a multi-step process regulated by several proteins at both transcriptional and post-transcriptional levels. Also, some environmental factors (carbon source, nitrogen and phosphate starvation, flavonoids) and stress conditions (osmolarity, ionic strength) affect EPS production. This paper discusses the recent data concerning the function of the genes required for EPS synthesis and the regulation of this process by several environmental signals. Up till now, the synthesis of rhizobial EPS has been best studied in two species, Sinorhizobium meliloti and Rhizobium leguminosarum. The latest data indicate that EPS synthesis in rhizobia undergoes very complex hierarchical regulation, in which proteins engaged in quorum sensing and the regulation of motility genes also participate. This finding enables a better understanding of the complex processes occurring in the rhizosphere which are crucial for successful colonization and infection of host plant roots.
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Affiliation(s)
- Monika Janczarek
- Department of Genetics and Microbiology, University of M. Curie-Skłodowska, Akademicka 19 st., Lublin 20-033, Poland; E-Mail: ; Tel.: +48-81-537-5974
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Malamud F, Torres PS, Roeschlin R, Rigano LA, Enrique R, Bonomi HR, Castagnaro AP, Marano MR, Vojnov AA. The Xanthomonas axonopodis pv. citri flagellum is required for mature biofilm and canker development. MICROBIOLOGY-SGM 2010; 157:819-829. [PMID: 21109564 DOI: 10.1099/mic.0.044255-0] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Xanthomonas axonopodis pv. citri (Xac) is the causative agent of citrus canker. This bacterium develops a characteristic biofilm on both biotic and abiotic surfaces. To evaluate the participation of the single flagellum of Xac in biofilm formation, mutants in the fliC (flagellin) and the flgE (hook) genes were generated. Swimming motility, assessed on 0.25 % agar plates, was markedly reduced in fliC and flgE mutants. However, the fliC and flgE mutants exhibited a flagellar-independent surface translocation on 0.5 % agar plates. Mutation of either the rpfF or the rpfC gene, which both encode proteins involved in cell-cell signalling mediated by diffusible signal factor (DSF), led to a reduction in both flagellar-dependent and flagellar-independent surface translocation, indicating a regulatory role for DSF in both types of motility. Confocal laser scanning microscopy of biofilms produced in static culture demonstrated that the flagellum is also involved in the formation of mushroom-shaped structures and water channels, and in the dispersion of biofilms. The presence of the flagellum was required for mature biofilm development on lemon leaf surfaces. The absence of flagellin produced a slight reduction in Xac pathogenicity and this reduction was more severe when the complete flagellum structure was absent.
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Affiliation(s)
- Florencia Malamud
- Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Saladillo 2468 C1440FFX, Ciudad de Buenos Aires, Argentina
| | - Pablo S Torres
- Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Saladillo 2468 C1440FFX, Ciudad de Buenos Aires, Argentina
| | - Roxana Roeschlin
- IBR - Depto. Microbiología, Facultad de Ciencias, Bioquímicas y Farmacéuticas, U.N.R. Suipacha 531, S2002LRK, Rosario, Argentina
| | - Luciano A Rigano
- Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Saladillo 2468 C1440FFX, Ciudad de Buenos Aires, Argentina
| | - Ramón Enrique
- IBR - Depto. Microbiología, Facultad de Ciencias, Bioquímicas y Farmacéuticas, U.N.R. Suipacha 531, S2002LRK, Rosario, Argentina
| | - Hernán R Bonomi
- Fundación Instituto Leloir-CONICET, Av. Patricias Argentinas 435 C1405BWE, Buenos Aires, Argentina
| | - Atilio P Castagnaro
- Estación Experimental Agroindustrial Obispo Colombres, Av. William Cross 3150, Las Talitas, Tucumán, Argentina
| | - María Rosa Marano
- IBR - Depto. Microbiología, Facultad de Ciencias, Bioquímicas y Farmacéuticas, U.N.R. Suipacha 531, S2002LRK, Rosario, Argentina
| | - Adrián A Vojnov
- Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará, CONICET, Saladillo 2468 C1440FFX, Ciudad de Buenos Aires, Argentina
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Bahlawane C, McIntosh M, Krol E, Becker A. Sinorhizobium meliloti regulator MucR couples exopolysaccharide synthesis and motility. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2008; 21:1498-1509. [PMID: 18842098 DOI: 10.1094/mpmi-21-11-1498] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In order to enter symbiosis with its legume partner, Sinorhizobium meliloti requires regulatory systems for the appropriate responses to its environment. For example, motility is required for the chemotactic movement of bacteria toward the compounds released by its host, and exopolysaccharides (EPS) are required for bacterial attachment to the root or for invasion of the infection thread. Previous research has shown that ExoR/ExoS/ChvI as well as the ExpR/Sin quorum-sensing system inversely regulate both motility and EPS production, although the regulation mechanisms were unknown. We were able to attribute the ExpR-mediated regulation of motility to the ability of ExpR to bind a DNA sequence upstream of visN when activated by N-acyl-homoserine lactone. Furthermore, MucR, previously characterized as a regulator of EPS production, also affected motility. MucR inhibited expression of rem encoding an activator of motility gene expression and, consequently, the expression of Rem-regulated genes such as flaF and flgG. Binding of MucR to the rem promoter region was demonstrated and a sequence motif similar to the previously identified MucR binding consensus was identified within this region. The swarming ability of S. meliloti Rm2011 was shown to depend on a functional ExpR/Sin quorum-sensing system and the production of both flagella and EPS. Finally, we propose a model for the coordination of motility and EPS synthesis in S. meliloti.
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Affiliation(s)
- Christelle Bahlawane
- Institute for Genome Research and Systems Biology, Center for Biotechnology, Bielefeld University, 33594 Bielefeld, Germany
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Rigano LA, Siciliano F, Enrique R, Sendín L, Filippone P, Torres PS, Qüesta J, Dow JM, Castagnaro AP, Vojnov AA, Marano MR. Biofilm formation, epiphytic fitness, and canker development in Xanthomonas axonopodis pv. citri. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:1222-30. [PMID: 17918624 DOI: 10.1094/mpmi-20-10-1222] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The phytopathogenic bacterium Xanthomonas axonopodis pv. citri is responsible for the canker disease affecting citrus plants throughout the world. Here, we have evaluated the role of bacterial attachment and biofilm formation in leaf colonization during canker development on lemon leaves. Crystal violet staining and confocal laser scanning microscopy analysis of X. axonopodis pv. citri strains expressing the green fluorescent protein were used to evaluate attachment and biofilm formation on abiotic and biotic (leaf) surfaces. Wild-type X. axonopodis pv. citri attached to and formed a complex, structured biofilm on glass in minimal medium containing glucose. Similar attachment and structured biofilm formation also were seen on lemon leaves. An X. axonopodis pv. citri gumB mutant strain, defective in production of the extracellular polysaccharide xanthan, did not form a structured biofilm on either abiotic or biotic surfaces. In addition, the X. axonopodis pv. citri gumB showed reduced growth and survival on leaf surfaces and reduced disease symptoms. These findings suggest an important role for formation of biofilms in the epiphytic survival of X. axonopodis pv. citri prior to development of canker disease.
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Affiliation(s)
- Luciano A Rigano
- Fundación Pablo Cassará, Centro de Ciencia y Tecnología Dr. Cesar Milstein, Saladillo 2468 C1440FFX, Ciudad de Buenos Aires, Argentina
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Wang Y, Lechno-Yossef S, Gong Y, Fan Q, Wolk CP, Xu X. Predicted glycosyl transferase genes located outside the HEP island are required for formation of heterocyst envelope polysaccharide in Anabaena sp. strain PCC 7120. J Bacteriol 2007; 189:5372-8. [PMID: 17483218 PMCID: PMC1951851 DOI: 10.1128/jb.00343-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
During maturation, heterocysts form an envelope layer of polysaccharide, called heterocyst envelope polysaccharide (HEP), whose synthesis depends on a cluster of genes, the HEP island, and on an additional, distant gene, hepB, or a gene immediately downstream from hepB. We show that HEP formation depends upon the predicted glycosyl transferase genes all4160 at a third locus and alr3699, which is adjacent to hepB and is cotranscribed with it. Mutations in the histidine kinase genes hepN and hepK appear to silence the promoter of hepB and incompletely down-regulate all4160.
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Affiliation(s)
- Yu Wang
- The State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, People's Republic of China
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15
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Gibson KE, Barnett MJ, Toman CJ, Long SR, Walker GC. The symbiosis regulator CbrA modulates a complex regulatory network affecting the flagellar apparatus and cell envelope proteins. J Bacteriol 2007; 189:3591-602. [PMID: 17237174 PMCID: PMC1855900 DOI: 10.1128/jb.01834-06] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sinorhizobium meliloti participates in a nitrogen-fixing symbiosis with legume plant host species of the genera Medicago, Melilotus, and Trigonella. We recently identified an S. meliloti two-component sensory histidine kinase, CbrA, which is absolutely required to establish a successful symbiosis with Medicago sativa (K. E. Gibson, G. R. Campbell, J. Lloret, and G. C. Walker, J. Bacteriol. 188:4508-4521, 2006). In addition to having a symbiotic defect, the cbrA::Tn5 mutant also has free-living phenotypes that suggest a cell envelope perturbation. Because the bases for these phenotypes are not well understood, we undertook an identification of CbrA-regulated genes. We performed a microarray analysis and compared the transcriptome of the cbrA::Tn5 mutant to that of the wild type. Our global analysis of gene expression identified 162 genes that are differentially expressed in the cbrA::Tn5 mutant, including those encoding proteins involved in motility and chemotaxis, metabolism, and cell envelope function. With regard to those genes with a known role in symbiosis, we observed increased expression of nine genes with overlapping functions in bacterial invasion of its host, which suggests that the mutant could be competent for invasion. Since these CbrA-repressed genes are vital to the invasion process, it appears that down-regulation of CbrA activity is important at this stage of nodule development. In contrast, our previous work showed that CbrA is required for bacteria to establish themselves within the host as nitrogen-fixing symbionts. Therefore, we propose a model in which CbrA functions as a developmental switch during symbiosis.
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Affiliation(s)
- Katherine E Gibson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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16
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Zhang XS, Cheng HP. Identification of Sinorhizobium meliloti early symbiotic genes by use of a positive functional screen. Appl Environ Microbiol 2006; 72:2738-48. [PMID: 16597978 PMCID: PMC1449070 DOI: 10.1128/aem.72.4.2738-2748.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The soil bacterium Sinorhizobium meliloti establishes nitrogen-fixing symbiosis with its leguminous host plant, alfalfa, following a series of continuous signal exchanges. The complexity of the changes of alfalfa root structures during symbiosis and the amount of S. meliloti genes with unknown functions raised the possibility that more S. meliloti genes may be required for early stages of the symbiosis. A positive functional screen of the entire S. meliloti genome for symbiotic genes was carried out using a modified in vivo expression technology. A group of genes and putative genes were found to be expressed in early stages of the symbiosis, and 23 of them were alfalfa root exudate inducible. These 23 genes were further separated into two groups based on their responses to apigenin, a known nodulation (nod) gene inducer. The group of six genes not inducible by apigenin included the lsrA gene, which is essential for the symbiosis, and the dgkA gene, which is involved in the synthesis of cyclic beta-1,2-glucan required for the S. meliloti-alfalfa symbiosis. In the group of 17 apigenin-inducible genes, most have not been previously characterized in S. meliloti, and none of them belongs to the nod gene family. The identification of this large group of alfalfa root exudate-inducible S. meliloti genes suggests that the interactions in the early stages of the S. meliloti and alfalfa symbiosis could be complex and that further characterization of these genes will lead to a better understanding of the symbiosis.
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Affiliation(s)
- Xue-Song Zhang
- Biological Sciences Department, Lehman College, The City University of New York, 250 Bedford Park Boulevard, West Bronx, NY 10468
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17
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Gibson KE, Campbell GR, Lloret J, Walker GC. CbrA is a stationary-phase regulator of cell surface physiology and legume symbiosis in Sinorhizobium meliloti. J Bacteriol 2006; 188:4508-21. [PMID: 16740957 PMCID: PMC1482976 DOI: 10.1128/jb.01923-05] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Accepted: 03/23/2006] [Indexed: 11/20/2022] Open
Abstract
Sinorhizobium meliloti produces an exopolysaccharide called succinoglycan that plays a critical role in promoting symbiosis with its host legume, alfalfa (Medicago sativa). We performed a transposon mutagenesis and screened for mutants with altered succinoglycan production and a defect in symbiosis. In this way, we identified a putative two-component histidine kinase associated with a PAS sensory domain, now designated CbrA (calcofluor-bright regulator A). The cbrA::Tn5 mutation causes overproduction of succinoglycan and results in increased accumulation of low-molecular-weight forms of this exopolysaccharide. Our results suggest the cbrA::Tn5 allele leads to this succinoglycan phenotype through increased expression of exo genes required for succinoglycan biosynthesis and modification. Interestingly, CbrA-dependent regulation of exo and exs genes is observed almost exclusively during stationary-phase growth. The cbrA::Tn5 mutant also has an apparent cell envelope defect, based on increased sensitivity to a number of toxic compounds, including the bile salt deoxycholate and the hydrophobic dye crystal violet. Growth of the cbrA mutant is also slowed under oxidative-stress conditions. The CbrA-regulated genes exsA and exsE encode putative inner membrane ABC transporters with a high degree of similarity to lipid exporters. ExsA is homologous to the Escherichia coli MsbA protein, which is required for lipopolysaccharide transport, while ExsE is a member of the eukaryotic family of ABCD/hALD peroxisomal membrane proteins involved in transport of very long-chain fatty acids, which are a unique component of the lipopolysaccharides of alphaproteobacteria. Thus, CbrA could play a role in regulating the lipopolysaccharide or lipoprotein components of the cell envelope.
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Affiliation(s)
- Katherine E Gibson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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18
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Skorupska A, Janczarek M, Marczak M, Mazur A, Król J. Rhizobial exopolysaccharides: genetic control and symbiotic functions. Microb Cell Fact 2006; 5:7. [PMID: 16483356 PMCID: PMC1403797 DOI: 10.1186/1475-2859-5-7] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 02/16/2006] [Indexed: 11/10/2022] Open
Abstract
Specific complex interactions between soil bacteria belonging to Rhizobium, Sinorhizobium, Mesorhizobium, Phylorhizobium, Bradyrhizobium and Azorhizobium commonly known as rhizobia, and their host leguminous plants result in development of root nodules. Nodules are new organs that consist mainly of plant cells infected with bacteroids that provide the host plant with fixed nitrogen. Proper nodule development requires the synthesis and perception of signal molecules such as lipochitooligosaccharides, called Nod factors that are important for induction of nodule development. Bacterial surface polysaccharides are also crucial for establishment of successful symbiosis with legumes. Sugar polymers of rhizobia are composed of a number of different polysaccharides, such as lipopolysaccharides (LPS), capsular polysaccharides (CPS or K-antigens), neutral β-1, 2-glucans and acidic extracellular polysaccharides (EPS). Despite extensive research, the molecular function of the surface polysaccharides in symbiosis remains unclear. This review focuses on exopolysaccharides that are especially important for the invasion that leads to formation of indetermined (with persistent meristem) type of nodules on legumes such as clover, vetch, peas or alfalfa. The significance of EPS synthesis in symbiotic interactions of Rhizobium leguminosarum with clover is especially noticed. Accumulating data suggest that exopolysaccharides may be involved in invasion and nodule development, bacterial release from infection threads, bacteroid development, suppression of plant defense response and protection against plant antimicrobial compounds. Rhizobial exopolysaccharides are species-specific heteropolysaccharide polymers composed of common sugars that are substituted with non-carbohydrate residues. Synthesis of repeating units of exopolysaccharide, their modification, polymerization and export to the cell surface is controlled by clusters of genes, named exo/exs, exp or pss that are localized on rhizobial megaplasmids or chromosome. The function of these genes was identified by isolation and characterization of several mutants disabled in exopolysaccharide synthesis. The effect of exopolysaccharide deficiency on nodule development has been extensively studied. Production of exopolysaccharides is influenced by a complex network of environmental factors such as phosphate, nitrogen or sulphur. There is a strong suggestion that production of a variety of symbiotically active polysaccharides may allow rhizobial strains to adapt to changing environmental conditions and interact efficiently with legumes.
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Affiliation(s)
- Anna Skorupska
- Department of General Microbiology, University of M. Curie-Skłodowska, Akademicka 19 st., 20-033 Lublin, Poland
| | - Monika Janczarek
- Department of General Microbiology, University of M. Curie-Skłodowska, Akademicka 19 st., 20-033 Lublin, Poland
| | - Małgorzata Marczak
- Department of General Microbiology, University of M. Curie-Skłodowska, Akademicka 19 st., 20-033 Lublin, Poland
| | - Andrzej Mazur
- Department of General Microbiology, University of M. Curie-Skłodowska, Akademicka 19 st., 20-033 Lublin, Poland
| | - Jarosław Król
- Department of General Microbiology, University of M. Curie-Skłodowska, Akademicka 19 st., 20-033 Lublin, Poland
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19
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Quester I, Becker A. Four promoters subject to regulation by ExoR and PhoB direct transcription of the Sinorhizobium melilotiexoYFQ operon involved in the biosynthesis of succinoglycan. J Mol Microbiol Biotechnol 2004; 7:115-32. [PMID: 15263816 DOI: 10.1159/000078655] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Succinoglycan (EPS I), the main acidic exopolysaccharide of Sinorhizobium meliloti, is required for the initiation and elongation of infection threads during nodulation of the host plant alfalfa. The gene products of the exoYFQ operon are involved in the first step of succinoglycan biosynthesis as well as in the polymerisation of subunits to the high-molecular-mass form of this exopolysaccharide. One promoter region that directs transcription of exoX and two promoter regions that drive transcription of exoY were mapped in the exoX-exoY intergenic region. The distal exoY promoter region containing three putative -10 promoter elements was active under standard growth conditions and was subject to ExoR-dependent regulation. Although this promoter region was stimulated in a phoB mutant, no PHO box-like sequences were found, suggesting an indirect regulatory effect of PhoB. The proximal promoter contains a PHO box-like sequence in the putative -35 region and was affected by low and high phosphate concentrations dependent on PhoB. In the case of deleted upstream regions, this promoter was also controlled by ExoR. An additional promoter displaying activity in exoR, mucR and phoB mutants under standard conditions was identified upstream of exoF. The putative -35 promoter element of this promoter is covered by a second PHO box-like sequence.
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Affiliation(s)
- Ingmar Quester
- Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, Bielefeld, Deutschland
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20
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Whitfield C, Paiment A. Biosynthesis and assembly of Group 1 capsular polysaccharides in Escherichia coli and related extracellular polysaccharides in other bacteria. Carbohydr Res 2004; 338:2491-502. [PMID: 14670711 DOI: 10.1016/j.carres.2003.08.010] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Extracellular and capsular polysaccharides (EPSs and CPSs) are produced by a wide range of bacteria, including important pathogens of humans, livestock, and plants. These polymers are major surface antigens and serve a variety of roles in virulence, depending on the biology of the producing organism. In addition to their importance in disease, some EPSs also have industrial applications as gelling and emulsifying agents. An understanding of the processes involved in the synthesis and regulation of CPSs and EPSs therefore potentially contributes to an understanding of the disease state, surface expression of protective antigens, and modulation of polymer structure to give defined physical properties. Escherichia coli has provided important model systems for EPS and CPS biosynthesis. Here we describe current knowledge concerning assembly of the Group 1 CPSs of E. coli and the conservation of similar mechanisms in other bacteria.
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Affiliation(s)
- Chris Whitfield
- Department of Microbiology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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21
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Cheng HP, Yao SY. The key Sinorhizobium meliloti succinoglycan biosynthesis gene exoY is expressed from two promoters. FEMS Microbiol Lett 2004; 231:131-6. [PMID: 14769477 PMCID: PMC3144747 DOI: 10.1016/s0378-1097(03)00952-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2003] [Revised: 11/19/2003] [Accepted: 12/10/2003] [Indexed: 11/16/2022] Open
Abstract
Bacterial exopolysaccharide, succinoglycan, plays an important role in eliciting infection thread formation, which is a key step in the establishment of Sinorhizobium meliloti-alfalfa (Medicago sativa) nitrogen fixing symbiosis. To understand the regulatory mechanisms that control production of succinoglycan, the expression of the key succinoglycan biosynthesis gene, exoY, was analyzed by constructing a set of nested deletions of the exoY promoter region. Two exoY promoters were identified based on the promoter activities and confirmed by direct detection of the transcripts. The expression from both promoters was induced in the exoR95 and exoS96 mutant backgrounds suggesting that both promoters are regulated by the ExoR protein and the ExoS/ChvI two-component signal transduction system. The identification of the exoY promoters provides additional avenue for further analysis of the role of succinoglycan in S. meliloti-alfalfa symbiosis.
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Affiliation(s)
- Hai-Ping Cheng
- Biological Sciences Department, Lehman College, the City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468, USA.
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22
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Niemeyer D, Becker A. The molecular weight distribution of succinoglycan produced by Sinorhizobium meliloti is influenced by specific tyrosine phosphorylation and ATPase activity of the cytoplasmic domain of the ExoP protein. J Bacteriol 2001; 183:5163-70. [PMID: 11489870 PMCID: PMC95393 DOI: 10.1128/jb.183.17.5163-5170.2001] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is thought that in the gram-negative soil bacterium Sinorhizobium meliloti the protein ExoP is involved in biosynthesis of the acidic exopolysaccharide succinoglycan (EPS I). The amounts and compositions of EPS I produced by mutants expressing ExoP proteins characterized by specific amino acid substitutions in the C-terminal cytoplasmic domain were analyzed. The cytoplasmic domain of the ExoP protein was shown to have ATPase activity. Mutations in the highly conserved Walker A ATP-binding motif prevented ATPase activity of the ExoP protein. Phenotypically, these mutations resulted in much lower levels of succinoglycan which consisted only of monomers of the octasaccharide repeating unit. The ExoP protein has similarities to proteins with autophosphorylating protein tyrosine kinase activity. We found that ExoP was phosphorylated on tyrosine and that site-directed mutagenesis of specific tyrosine residues in the cytoplasmic domain of ExoP resulted in an altered ratio of low-molecular-weight succinoglycan to high-molecular-weight succinoglycan.
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Affiliation(s)
- D Niemeyer
- Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, D-33501 Bielefeld, Germany
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23
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Finan TM, Weidner S, Wong K, Buhrmester J, Chain P, Vorhölter FJ, Hernandez-Lucas I, Becker A, Cowie A, Gouzy J, Golding B, Pühler A. The complete sequence of the 1,683-kb pSymB megaplasmid from the N2-fixing endosymbiont Sinorhizobium meliloti. Proc Natl Acad Sci U S A 2001; 98:9889-94. [PMID: 11481431 PMCID: PMC55548 DOI: 10.1073/pnas.161294698] [Citation(s) in RCA: 249] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Analysis of the 1,683,333-nt sequence of the pSymB megaplasmid from the symbiotic N(2)-fixing bacterium Sinorhizobium meliloti revealed that the replicon has a high gene density with a total of 1,570 protein-coding regions, with few insertion elements and regions duplicated elsewhere in the genome. The only copies of an essential arg-tRNA gene and the minCDE genes are located on pSymB. Almost 20% of the pSymB sequence carries genes encoding solute uptake systems, most of which were of the ATP-binding cassette family. Many previously unsuspected genes involved in polysaccharide biosynthesis were identified and these, together with the two known distinct exopolysaccharide synthesis gene clusters, show that 14% of the pSymB sequence is dedicated to polysaccharide synthesis. Other recognizable gene clusters include many involved in catabolic activities such as protocatechuate utilization and phosphonate degradation. The functions of these genes are consistent with the notion that pSymB plays a major role in the saprophytic competence of the bacteria in the soil environment.
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Affiliation(s)
- T M Finan
- Department of Biology, McMaster University, Hamilton, ON, Canada.
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24
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Yildiz FH, Dolganov NA, Schoolnik GK. VpsR, a Member of the Response Regulators of the Two-Component Regulatory Systems, Is Required for Expression of vps Biosynthesis Genes and EPS(ETr)-Associated Phenotypes in Vibrio cholerae O1 El Tor. J Bacteriol 2001; 183:1716-26. [PMID: 11160103 PMCID: PMC95057 DOI: 10.1128/jb.183.5.1716-1726.2001] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The rugose colonial variant of Vibrio cholerae O1 El Tor produces an exopolysaccharide (EPS(ETr)) that enables the organism to form a biofilm and to resist oxidative stress and the bactericidal action of chlorine. Transposon mutagenesis of the rugose variant led to the identification of vpsR, which codes for a homologue of the NtrC subclass of response regulators. Targeted disruption of vpsR in the rugose colony genetic background yielded a nonreverting smooth-colony morphotype that produced no detectable EPS(ETr) and did not form an architecturally mature biofilm. Analysis of two genes, vpsA and vpsL, within the vps cluster of EPS(ETr) biosynthesis genes revealed that their expression is induced above basal levels in the rugose variant, compared to the smooth colonial variant, and requires vpsR. These results show that VpsR functions as a positive regulator of vpsA and vpsL and thus acts to positively regulate EPS(ETr) production and biofilm formation.
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Affiliation(s)
- F H Yildiz
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University Medical School, Stanford, California 94305, USA.
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25
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Almirón-Roig E, Mulholland F, Gasson MJ, Griffin AM. The complete cps gene cluster from Streptococcus thermophilus NCFB 2393 involved in the biosynthesis of a new exopolysaccharide. MICROBIOLOGY (READING, ENGLAND) 2000; 146 ( Pt 11):2793-2802. [PMID: 11065358 DOI: 10.1099/00221287-146-11-2793] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The cpsFGHIJKL genes from the cps cluster of Streptococcus thermophilus NCFB 2393 involved in the biosynthesis of EPS were identified, cloned and nucleotide sequenced. The complete cps cluster is contained on an approximately 11.2 kb chromosomal region which contains 12 ORFs, including the previously cloned cpsABCDE genes. Functions were assigned to some of the predicted gene products on the basis of homology to known sequences as follows: cpsK encodes a protein thought to be involved in the polymerization and export of the polysaccharide; cpsE, cpsF, cpsG, cpsH, cpsI and cpsJ encode putative sugar transferases. Two insertion sequences, IS1193 and ISS1, were identified within and flanking the 3' end of the cps cluster respectively. Analysis of the expression of the cpsE gene in Escherichia coli demonstrated that it encodes a glucose-1-phosphate transferase; the enzyme which catalyses the first step in EPS biosynthesis in S. thermophilus NCFB 2393.
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Affiliation(s)
- Eva Almirón-Roig
- Institute of Food Research, Norwich Research Park, Colney Lane, NR4 7UA Norwich, UK1
| | - Francis Mulholland
- Institute of Food Research, Norwich Research Park, Colney Lane, NR4 7UA Norwich, UK1
| | - Michael J Gasson
- Institute of Food Research, Norwich Research Park, Colney Lane, NR4 7UA Norwich, UK1
| | - Annette M Griffin
- Institute of Food Research, Norwich Research Park, Colney Lane, NR4 7UA Norwich, UK1
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26
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Martín M, Lloret J, Sánchez-Contreras M, Bonilla I, Rivilla R. MucR is necessary for galactoglucan production in Sinorhizobium meliloti EFB1. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2000; 13:129-135. [PMID: 10656595 DOI: 10.1094/mpmi.2000.13.1.129] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Sinorhizobium meliloti can produce two types of acidic exopolysaccharides, succinoglycan and galactoglucan, that are interchangeable for infection of alfalfa nodules. Strain SU47 and derivatives produce only succinoglycan, unless it grows under phosphate limitation or carries a mutation in either of two regulatory loci, mucR or expR. It has been proposed that MucR acts as a transcriptional repressor that blocks the expression of the exp genes responsible for galactoglucan production. Strain EFB1 simultaneously produces both exopolysaccharides. Heterologous expression of lacZ transcriptional fusions of the expE promoters has shown that genetic background is more important that promoter sequence for exp gene expression, since expE promoters from both strains are expressed at high level in EFB1 and not in SU47. We have found that mucR is present in mucoid and nonmucoid strains, and in EFB1 differs from SU47 in only one conservative amino acid change. MucR proteins from both strains are interchangeable. An mucR mutant of EFB1 cannot produce galactoglucan and does not express mucS.
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Affiliation(s)
- M Martín
- Departamento de Biología, Universidad Autónoma de Madrid, Spain
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27
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Vizcaíno N, Cloeckaert A, Zygmunt MS, Fernández-Lago L. Molecular characterization of a Brucella species large DNA fragment deleted in Brucella abortus strains: evidence for a locus involved in the synthesis of a polysaccharide. Infect Immun 1999; 67:2700-12. [PMID: 10338472 PMCID: PMC96573 DOI: 10.1128/iai.67.6.2700-2712.1999] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A Brucella melitensis 16M DNA fragment of 17,119 bp, which contains a large region deleted in B. abortus strains and DNA flanking one side of the deletion, has been characterized. In addition to the previously identified omp31 gene, 14 hypothetical genes have been identified in the B. melitensis fragment, most of them showing homology to genes involved in the synthesis of a polysaccharide. Considering that 10 of the 15 genes are missing in B. abortus and that all the polysaccharides described in the Brucella genus (lipopolysaccharide, native hapten, and polysaccharide B) have been detected in all the species, it seems likely that the genes described here might be part of a cluster for the synthesis of a novel Brucella polysaccharide. Several polysaccharides have been identified as important virulence factors, and the discovery of a novel polysaccharide in the brucellae which is probably not synthesized in B. abortus might be interesting for a better understanding of the pathogenicity and host preference differences observed between the Brucella species. However, the possibility that the genes described in this paper no longer encode the synthesis of a polysaccharide cannot be excluded. Brucellae belong to the alpha-2 subdivision of the class Proteobacteria, which includes other microorganisms living in association with eucaryotic cells, some of them synthesizing extracellular polysaccharides involved in the interaction with the host cell. The genes described in this paper might be a remnant of the common ancestor of the alpha-2 subdivision of the class Proteobacteria, and the brucellae might have lost such extracellular polysaccharide during evolution if it was not necessary for survival or for establishment of the infectious process. Nevertheless, further studies are necessary to identify the entire DNA fragment missing in B. abortus strains and to elucidate the mechanism responsible for such deletion, since only 9,948 bp of the deletion was present in the sequenced B. melitensis DNA fragment.
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Affiliation(s)
- N Vizcaíno
- Departamento de Microbiología y Genética, Edificio Departamental, Universidad de Salamanca, 37007 Salamanca, Spain
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28
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Król J, Wielbo J, Mazur A, Kopcińska J, Lotocka B, Golinowski W, Skorupska A. Molecular characterization of pssCDE genes of Rhizobium leguminosarum bv. trifolii strain TA1: pssD mutant is affected in exopolysaccharide synthesis and endocytosis of bacteria. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 1998; 11:1142-1148. [PMID: 9805402 DOI: 10.1094/mpmi.1998.11.11.1142] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have identified the three genes pssCDE in Rhizobium leguminosarum bv. trifolii TA1. Even though they were almost identical to earlier identified pssCDE genes of R. leguminosarum, they differed in gene lengths and gene overlaps. The predicted gene products of pssCDE genes shared significant homology to prokaryotic glycosyl transferases involved in exopolysaccharide synthesis. The Tn5 insertion in pssD created the nonmucoid mutant that induced non-nitrogen-fixing nodules. The microscopic analysis of the nodules, induced on Trifolium pratense by the pssD133 mutant, showed abnormally enlarged infection threads densely packed with bacteria, which were released from the infection threads in an unusual way. The symbiosomes were observed very rarely and the nodule remained almost empty. Symbiotic phenotype of the pssD133 suggested a correlation between this mutation and defective endocytosis of bacteria into nodule cells.
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Affiliation(s)
- J Król
- Department of General Microbiology, M. Curie-Sklodowska University, Lublin, Poland
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29
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Milcamps A, Ragatz DM, Lim P, Berger KA, de Bruijin FJ. Isolation of carbon- and nitrogen-deprivation-induced loci of Sinorhizobium meliloti 1021 by Tn5-luxAB mutagenesis. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 11):3205-3218. [PMID: 9846756 DOI: 10.1099/00221287-144-11-3205] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Soil bacteria, such as Sinorhizobium meliloti, are subject to variation in environmental conditions, including carbon- and nitrogen-deprivation. The ability of bacteria to sense changes in their environment and respond accordingly is of vital importance to their survival and persistence in the soil and rhizosphere. A derivative of Tn5 which creates transcriptional fusions to the promoterless luxAB genes was used to mutagenize S. meliloti 1021 and 5000 insertion mutants were subsequently screened for gene fusions induced by selected environmental stresses. The isolation of 21 gene fusions induced by nitrogen-deprivation and 12 induced by carbon-deprivation is described. Cloning and partial DNA sequence analysis of the transposon-tagged loci revealed a variety of novel genes, as well as S. meliloti genes with significant similarity to known bacterial loci. In addition, nodule occupancy studies were carried out with selected Tn5-luxAB insertion mutants to examine the role of the tagged genes in competition.
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Affiliation(s)
- Anne Milcamps
- MSU-DOE Plant Research Laboratory,Rm 306, Plant Biology Building University, East Lansing, MI 48824,USA
- NSF Center for Microbial Ecology, University,East Lansing, MI 48824,USA
| | - Daniel M Ragatz
- MSU-DOE Plant Research Laboratory,Rm 306, Plant Biology Building University, East Lansing, MI 48824,USA
- NSF Center for Microbial Ecology, University,East Lansing, MI 48824,USA
| | - PyungOk Lim
- MSU-DOE Plant Research Laboratory,Rm 306, Plant Biology Building University, East Lansing, MI 48824,USA
- NSF Center for Microbial Ecology, University,East Lansing, MI 48824,USA
| | - Kelly A Berger
- MSU-DOE Plant Research Laboratory,Rm 306, Plant Biology Building University, East Lansing, MI 48824,USA
| | - Frans J de Bruijin
- NSF Center for Microbial Ecology, University,East Lansing, MI 48824,USA
- Department of Microbiology, Michigan State University,East Lansing, MI 48824,USA
- MSU-DOE Plant Research Laboratory,Rm 306, Plant Biology Building University, East Lansing, MI 48824,USA
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30
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Vojnov AA, Zorreguieta A, Dow JM, Daniels MJ, Dankert MA. Evidence for a role for the gumB and gumC gene products in the formation of xanthan from its pentasaccharide repeating unit by Xanthomonas campestris. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 6):1487-1493. [PMID: 9639919 DOI: 10.1099/00221287-144-6-1487] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The biosynthesis of the extracellular polysaccharide xanthan in Xanthomonas campestris pv. campestris is directed by a cluster of 12 genes, gumB-gumM. Several xanthan-deficient mutants of the wild-type strain 8004 have previously been described which carry Tn5 insertions in this region of the chromosome. Here it is shown that the transposon insertion in one of these mutants, strain 8397, is located 15 bp upstream of the translational start site of the gumB gene. EDTA-treated cells of strain 8397 were able to synthesize the lipid-linked pentasaccharide repeating unit of xanthan from the three nucleotide sugar donors (UDP-glucose, GDP-mannose and UDP-glucuronic acid) but were unable to polymerize the pentasaccharide into mature xanthan. A subclone of the gum gene cluster carrying gumB and gumC restored xanthan production to strain 8397 to levels approximately 28% of the wild-type. In contrast, subclones carrying gumB or gumC alone were not effective. These results are discussed with reference to previous speculations, based on computer analysis, that gumB and gumC are both involved in the translocation of xanthan across the bacterial membranes.
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Affiliation(s)
- Adrián A Vojnov
- Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales and Consejo Nacional de Investigaciones Cientificas y Técnicas, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Angeles Zorreguieta
- Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales and Consejo Nacional de Investigaciones Cientificas y Técnicas, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - J Maxwell Dow
- The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - Michael J Daniels
- The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - Marcelo A Dankert
- Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales and Consejo Nacional de Investigaciones Cientificas y Técnicas, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
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31
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Niehaus K, Becker A. The role of microbial surface polysaccharides in the Rhizobium-legume interaction. Subcell Biochem 1998; 29:73-116. [PMID: 9594645 DOI: 10.1007/978-1-4899-1707-2_3] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- K Niehaus
- Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, Germany
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32
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Katzen F, Ferreiro DU, Oddo CG, Ielmini MV, Becker A, Pühler A, Ielpi L. Xanthomonas campestris pv. campestris gum mutants: effects on xanthan biosynthesis and plant virulence. J Bacteriol 1998; 180:1607-17. [PMID: 9537354 PMCID: PMC107069 DOI: 10.1128/jb.180.7.1607-1617.1998] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Xanthan is an industrially important exopolysaccharide produced by the phytopathogenic, gram-negative bacterium Xanthomonas campestris pv. campestris. It is composed of polymerized pentasaccharide repeating units which are assembled by the sequential addition of glucose-1-phosphate, glucose, mannose, glucuronic acid, and mannose on a polyprenol phosphate carrier (L. Ielpi, R. O. Couso, and M. A. Dankert, J. Bacteriol. 175:2490-2500, 1993). A cluster of 12 genes in a region designated xpsI or gum has been suggested to encode proteins involved in the synthesis and polymerization of the lipid intermediate. However, no experimental evidence supporting this suggestion has been published. In this work, from the biochemical analysis of a defined set of X. campestris gum mutants, we report experimental data for assigning functions to the products of the gum genes. We also show that the first step in the assembly of the lipid-linked intermediate is severely affected by the combination of certain gum and non-gum mutations. In addition, we provide evidence that the C-terminal domain of the gumD gene product is sufficient for its glucosyl-1-phosphate transferase activity. Finally, we found that alterations in the later stages of xanthan biosynthesis reduce the aggressiveness of X. campestris against the plant.
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Affiliation(s)
- F Katzen
- Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales, UBA, and CONICET, Buenos Aires, Argentina
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33
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García-de los Santos A, Brom S. Characterization of two plasmid-borne lps beta loci of Rhizobium etli required for lipopolysaccharide synthesis and for optimal interaction with plants. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 1997; 10:891-902. [PMID: 9304861 DOI: 10.1094/mpmi.1997.10.7.891] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
In Rhizobium etli CFN42, both the symbiotic plasmid (pd) and plasmid b (pb) are required for effective bean nodulation. This is due to the presence on pb of a region (lps beta) involved in lipopolysaccharide (LPS) biosynthesis. We report here the genetic array and functional features of this plasmid-borne region. The sequence analysis of a 3,595-bp fragment revealed the presence of a transcriptional unit integrated by two open reading frames (lps beta 1 and lps beta 2) essential for LPS biosynthesis and symblosis. The lps beta 1 encodes a putative 193 amino acid polypeptide that shows strong homology with glucosyl-1P and galactosyl-1P transferases. The deduced amino acid sequence of the protein encoded by lps beta 2 was very similar to that of proteins involved in surface polysaccharide biosynthesis, such as Pseudomonas aeruginosa WpbM, Bordetella pertussis BpIL, and Yersinia enterocolitica TrsG. DNA sequences homologous to lps beta 1 and lps beta 2 of R. etli CFN42 were consistently found in functionally equivalent plasmids of R. etli, R. leguminosarum bv. viciae, and R. leguminosarum hv. trifolii strains, but not in R. meliloti, R. loti, R. tropici, R. fredii, Bradyrhizobium, Azorhizobium, and Agrobacterium tumefaciens. Even though Rhizobium and Agrobacterium do not share lps beta sequences, their presence is required for crown-gall tumor induction by R. etli transconjugants carrying the Ti plasmid.
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Affiliation(s)
- A García-de los Santos
- Departamento de Genética Molecular, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Cuemavaca, Morelos, México
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Fallarino A, Mavrangelos C, Stroeher UH, Manning PA. Identification of additional genes required for O-antigen biosynthesis in Vibrio cholerae O1. J Bacteriol 1997; 179:2147-53. [PMID: 9079898 PMCID: PMC178949 DOI: 10.1128/jb.179.7.2147-2153.1997] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The cloning and expression of the genes encoding the Vibrio cholerae O1 lipopolysaccharide O antigen in a heterologous host have been described previously (P. A. Manning, M. W. Heuzenroeder, J. Yeadon, D. I. Leavesley, P. R. Reeves, and D. Rowley, Infect. Immun. 53:272-277, 1986). It was thus assumed that all the genes required for O-antigen expression were located on a 20-kb SacI restriction fragment. We present evidence for a number of other as yet undescribed genes that are essential for O-antigen biosynthesis in V. cholerae O1 and that these genes are somehow complemented in Escherichia coli K-12. The two genes termed Vibrio cholerae rfbV and rfbU are transcribed in the opposite orientation from the rest of the rfb operon, whereas the galE dehydratase and rfbP (Salmonella enterica) homologs, designated ORF35x7 and rfbW, respectively, are transcribed in the same orientation. The evidence presented here, using chromosomal insertion mutants, clearly shows that the three genes now designated rfbV, rfbU, and rfbW appear to be accessory rfb genes and are essential for O-antigen biosynthesis in V. cholerae but that ORF35x7 is not.
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Affiliation(s)
- A Fallarino
- Department of Microbiology and Immunology, The University of Adelaide, South Australia
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35
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van Workum WA, Canter Cremers HC, Wijfjes AH, van der Kolk C, Wijffelman CA, Kijne JW. Cloning and characterization of four genes of Rhizobium leguminosarum bv. trifolii involved in exopolysaccharide production and nodulation. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 1997; 10:290-301. [PMID: 9057334 DOI: 10.1094/mpmi.1997.10.2.290] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Four different genes of Rhizobium leguminosarum bv. trifolii strain RBL5599 involved in exopolysaccharide (EPS) production were identified by complementation of Tn5-induced EPS-deficient mutants (Exo mutants) with a cosmid bank. On one cosmid pssA was located, which was found to be almost identical to the pss4 gene from R. leguminosarum bv. viciae VF39 and highly homologous to a family of glycosyl transferases. Two pssA mutants, exo2 and exo4, were characterized and found to produce 19 and 1% of the wild-type amount of EPS, respectively. The three other genes were found to be closely linked on a different complementing cosmid. pssC revealed similarity to exoM and exoW of R. meliloti, both encoding glucosyl transferases involved in the synthesis of succinoglycan. A mutation in this gene (mutant exo50) did reduce EPS synthesis to 27% of the wild-type amount. We found an operon closely linked to pssC, consisting of two overlapping genes, pssD and pssE, that is essential for EPS production. Homology of pssD and pssE was found with cps14F and cps14G of Streptococcus pneumoniae, respectively: two genes responsible for the second step in capsule polysaccharide synthesis. Furthermore, pssD and pssE were homologous to the 5' and 3' parts, respectively, of spsK of Sphingomonas S88, which encodes a putative glycosyl transferase. Structural analysis of EPS produced by Exo mutants exo2, exo4, and exo50 showed it to be identical to that of the parental strain RBL5599, with the exception of acetyl groups esterified to one of the glucose residues being absent.
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Affiliation(s)
- W A van Workum
- Institute of Molecular Plant Sciences, Leiden University, The Netherlands.
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36
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Becker A, Rüberg S, Küster H, Roxlau AA, Keller M, Ivashina T, Cheng HP, Walker GC, Pühler A. The 32-kilobase exp gene cluster of Rhizobium meliloti directing the biosynthesis of galactoglucan: genetic organization and properties of the encoded gene products. J Bacteriol 1997; 179:1375-84. [PMID: 9023225 PMCID: PMC178839 DOI: 10.1128/jb.179.4.1375-1384.1997] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Proteins directing the biosynthesis of galactoglucan (exopolysaccharide II) in Rhizobium meliloti Rm2011 are encoded by the exp genes. Sequence analysis of a 32-kb DNA fragment of megaplasmid 2 containing the exp gene cluster identified previously (J. Glazebrook and G. C. Walker, Cell 56:661-672, 1989) revealed the presence of 25 open reading frames. Homologies of the deduced exp gene products to proteins of known function suggested that the exp genes encoded four proteins involved in the biosynthesis of dTDP-glucose and dTDP-rhamnose, six glycosyltransferases, an ABC transporter complex homologous to the subfamily of peptide and protein export complexes, and a protein homologous to Rhizobium NodO proteins. In addition, homologies of three Exp proteins to transcriptional regulators, methyltransferases, and periplasmic binding proteins were found. The positions of 26 Tn5 insertions in the exp gene cluster were determined, thus allowing the previously described genetic map to be correlated with the sequence. Operon analysis revealed that the exp gene cluster consists of five complementation groups. In comparison to the wild-type background, all exp complementation groups were transcribed at a substantially elevated level in the regulatory mucR mutant.
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Affiliation(s)
- A Becker
- Lehrstuhl für Genetik, Fakultät fur Biologie, Universität Bielefeld,Germany
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37
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Abstract
Bacterial polysaccharides are usually associated with the outer surface of the bacterium. They can form an amorphous layer of extracellular polysaccharide (EPS) surrounding the cell that may be further organized into a distinct structure termed a capsule. Additional polysaccharide molecules such as lipopolysaccharide (LPS) or lipooligosaccharide (LOS) may also decorate the cell surface. Polysaccharide capsules may mediate a number of biological processes, including invasive infections of human beings. Discussed here are the genetics and biochemistry of selected bacterial capsular polysaccharides and the basis of capsule diversity but not the genetics and biochemistry of LPS biosynthesis (for reviews see 100, 140).
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Affiliation(s)
- I S Roberts
- School of Biological Siences, University of Manchester, United Kingdom
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38
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Yamazaki M, Thorne L, Mikolajczak M, Armentrout RW, Pollock TJ. Linkage of genes essential for synthesis of a polysaccharide capsule in Sphingomonas strain S88. J Bacteriol 1996; 178:2676-87. [PMID: 8626338 PMCID: PMC177995 DOI: 10.1128/jb.178.9.2676-2687.1996] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Several structurally related capsular polysaccharides that are secreted by members of the genus Sphingomonas are being developed as aqueous rheological control agents for diverse industrial and food applications. They include gellan (S-60), welan (S-130), rhamsan (S-194), S-657, S-88, S-198, S-7, and NW-11. We refer to these polysaccharides as sphingans, after the genus name. This paper characterizes the first gene cluster isolated from a Sphingomonas species (S88) that is required for capsule synthesis. Overlapping DNA segments which spanned about 50 kbp of S88 DNA restored the synthesis of sphingan S-88 in capsule-negative mutants. The mutations were mapped into functional complementation groups, and the contiguous nucleotide sequence for the 29-kbp cluster was determined. The genetic complementation map and the DNA sequences were interpreted as an extended multicistronic locus containing genes essential for the assembly and secretion of polysaccharide S-88. Many of the deduced amino acid sequences were similar to gene products from other polysaccharide-secreting bacteria such as Rhizobium meliloti (succinoglycan), Xanthomonas campestris (xanthan gum), and Salmonella enterica (O antigen). The S88 locus contained a four-gene operon for the biosynthesis of dTDP-L-rhamnose, an essential precursor for the sphingans. Unexpectedly, there were also two genes for secretion of a lytic or toxin-like protein nested within the polysaccharide cluster. The conservation and linkage of genes that code for a defensive capsule and genes for secretion of an offensive lysin or toxin suggest a heretofore unknown pathogenic life history for Sphingomonas strain S88.
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Affiliation(s)
- M Yamazaki
- Shin-Etsu Bio, Inc., San Diego, California 92121, USA
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39
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Wang L, Liu D, Reeves PR. C-terminal half of Salmonella enterica WbaP (RfbP) is the galactosyl-1-phosphate transferase domain catalyzing the first step of O-antigen synthesis. J Bacteriol 1996; 178:2598-604. [PMID: 8626328 PMCID: PMC177985 DOI: 10.1128/jb.178.9.2598-2604.1996] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We previously showed that the product of the wbaP gene of Salmonella enterica serovar Typhimurium has two functions: it is involved in the first step of O-antigen synthesis (the galactosyltransferase [GT] function) and in a later step (the T function), first thought to be the flipping of the O-antigen subunit on undecaprenyl pyrophosphate from the cytoplasmic face to the periplasmic face of the cytoplasmic membrane. We now locate two wbaP(T) mutations within the first half of the wbaP gene by sequencing. Both mutants retain GT activity, although one was a frameshift mutation resulting in a stop codon 10 codons after the frameshift to give an open reading frame containing only 138 of the 476 codons in WbaP. We also show that there is a secondary translation starting within the wbaP gene resulting in the synthesis of a polypeptide with GT activity. These results indicate that the N- and C-terminal halves of WbaP are the T and GT functional domains, respectively. We now propose that the T block operates prior to the flippase function, probably at the release of undecaprenyl pyrophosphate-linked galactose from WbaP.
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Affiliation(s)
- L Wang
- Department of Microbiology, The University of Sydney, New South Wales, Australia
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40
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Griffin AM, Morris VJ, Gasson MJ. Identification, cloning and sequencing the aceA gene involved in acetan biosynthesis in Acetobacter xylinum. FEMS Microbiol Lett 1996; 137:115-21. [PMID: 8935665 DOI: 10.1111/j.1574-6968.1996.tb08092.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The aceA gene from Acetobacter xylinum was identified and cloned from a genomic DNA library. The complete DNA sequence was determined and computer analysis of the translated gene sequence revealed homology with the deduced amino acid sequence of gumD from Xanthomonas campestris. Therefore aceA is likely to encode the phosphate-prenyl glucose l-phosphate transferase catalyzing the first step in acetan biosynthesis in A. xylinum.
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Affiliation(s)
- A M Griffin
- Institute of Food Research, Norwich Laboratory, Colney, UK. annette.griffin/b
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41
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Stingele F, Neeser JR, Mollet B. Identification and characterization of the eps (Exopolysaccharide) gene cluster from Streptococcus thermophilus Sfi6. J Bacteriol 1996; 178:1680-90. [PMID: 8626297 PMCID: PMC177854 DOI: 10.1128/jb.178.6.1680-1690.1996] [Citation(s) in RCA: 212] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We report the identification and characterization of the eps gene cluster of Streptococcus thermophilus Sfi6 required for exopolysaccharide (EPS) synthesis. This report is the first genetic work concerning EPS production in a food microorganism. The EPS secreted by this strain consists of the following tetrasaccharide repeating unit:-->3)-beta-D-Galp-(1-->3)-[alpha-D-Galp-(1-->6)]-beta-D- D-Galp-(1-->3)-alpha-D-Galp-D-GalpNAc-(1-->. The genetic locus The genetic locus was identified by Tn916 mutagenesis in combination with a plate assay to identify Eps mutants. Sequence analysis of the gene region, which was obtained from subclones of a genomic library of Sfi6, revealed a 15.25-kb region encoding 15 open reading frames. EPS expression in the non-EPS-producing heterologous host, Lactococcus lactis MG1363, showed that within the 15.25-kb region, a region with a size of 14.52 kb encoding the 13 genes epsA to epsM was capable of directing EPS synthesis and secretion in this host. Homology searches of the predicted proteins in the Swiss-Prot database revealed high homology (40 to 68% identity) for epsA, B, C, D, and E and the genes involved in capsule synthesis in Streptococcus pneumoniae and Streptococcus agalactiae. Moderate to low homology (37 to 18% identity) was detected for epsB, D, F, and H and the genes involved in capsule synthesis in Staphylococcus aureus for epsC, D, and E and the genes involved in exopolysaccharide I (EPSI) synthesis in Rhizobium meliloti for epsC to epsJ and the genes involved in lipopolysaccharide synthesis in members of the Enterobacteriaceae, and finally for eps K and lipB of Neisseria meningitidis. Genes (epsJ, epsL, and epsM) for which the predicted proteins showed little or no homology with proteins in the Swiss-Prot database were shown to be involved in EPS synthesis by single-crossover gene disruption experiments.
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Affiliation(s)
- F Stingele
- Nestlé Research Center, Nestec Ltd., Lausanne, Switzerland
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42
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Becker A, Küster H, Niehaus K, Pühler A. Extension of the Rhizobium meliloti succinoglycan biosynthesis gene cluster: identification of the exsA gene encoding an ABC transporter protein, and the exsB gene which probably codes for a regulator of succinoglycan biosynthesis. MOLECULAR & GENERAL GENETICS : MGG 1995; 249:487-97. [PMID: 8544814 DOI: 10.1007/bf00290574] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Two new genes, designated exsA and exsB, were identified adjacent to the 24 kb exo gene cluster of Rhizobium meliloti, which is involved in succinoglycan (EPS I) biosynthesis. The derived amino acid sequence of ExsA displayed significant homologies to ATP binding cassette (ABC) transporter proteins. R. meliloti strains mutated in exsA were characterized by a decreased ratio of HMW to LMW EPS I, indicating a function for ExsA in EPS I biosynthesis. The R. meliloti NdvA protein, which is involved in the transport of cyclic beta-(1,2)-glucans, was identified as the closest homologue of ExsA. R. meliloti exsB mutants produced a three-fold increased amount of EPS I in comparison to the wild-type strain. In contrast, high copy number of exsB resulted in a decrease in the EPS I level to 20% of wild type, indicating that the exsB gene product can negatively influence EPS I biosynthesis. It was demonstrated that this influence is not due to transcriptional regulation of the exo genes by the exsB gene product. By plasmid integration it was shown that exsA and exsB represent monocistronic transcription units.
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Affiliation(s)
- A Becker
- Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, Federal Republic of Germany
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43
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Becker A, Niehaus K, Pühler A. Low-molecular-weight succinoglycan is predominantly produced by Rhizobium meliloti strains carrying a mutated ExoP protein characterized by a periplasmic N-terminal domain and a missing C-terminal domain. Mol Microbiol 1995; 16:191-203. [PMID: 7565082 DOI: 10.1111/j.1365-2958.1995.tb02292.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The membrane topology of the Rhizobium meliloti 2011 ExoP protein involved in polymerization and export of succinoglycan was analysed by translational fusions of lacZ and phoA reporter genes to the exoP gene. Based on this analysis, the ExoP protein could be divided into an N-terminal domain mainly located in the periplasmic space and a C-terminal domain located in the cytoplasm. Whereas the C-terminal domain of ExoP is characterized by a potential nucleotide-binding motif, the N-terminal ExoP domain contains the sequence motif 'PX2PX4SPKX11GXMXG', which is also present in proteins involved in the determination of O-antigen chain length. R. meliloti strains carrying mutated exoP* genes, exclusively encoding the N-terminal ExoP domain, produced a reduced amount of succinoglycan. This reduction could be suppressed by a mutation in the regulatory gene exoR. The ratio of low-molecular-weight to high-molecular-weight succinoglycan was significantly increased in the exoP* mutant strain. In the exoP*/exoR mutant strain only low-molecular-weight succinoglycan could be detected. Based on sequence homologies and similar hydropathic profiles, the N-terminal domain of ExoP was proposed to be a member of a protein family thought to be involved in polysaccharide chain-length determination.
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Affiliation(s)
- A Becker
- Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, Germany
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44
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Bugert P, Geider K. Molecular analysis of the ams operon required for exopolysaccharide synthesis of Erwinia amylovora. Mol Microbiol 1995; 15:917-33. [PMID: 7596293 DOI: 10.1111/j.1365-2958.1995.tb02361.x] [Citation(s) in RCA: 157] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A 16 kb transcript of the ams region, which is essential for biosynthesis of amylovoran, the acidic exopolysaccharide of Erwinia amylovora, was detected by Northern hybridization analysis. The positive regulator RcsA enhanced transcription of the large mRNA from the ams operon. The nucleotide sequence of this area revealed 12 open reading frames (ORFs), which are all transcribed in the same direction. Five ORFs corresponded to the previously mapped genes amsA to amsE. Sequence analysis of the insertion sites of several Tn5 mutations confirmed these data. Tn5 or site-directed mutagenesis of the ORFs 477, 377, 144, and 743 revealed an amylovoran-deficient phenotype, and the newly identified genes were named amsG, amsH, amsI, and amsF, respectively. The predicted amino acid sequence of AmsG is highly homologous to galactosyl-1-phosphate undecaprenylphosphate transferases. AmsB and AmsD are similar to other glycosyl transferases, and AmsH may be related to BexD. A significant homology to mammalian phosphatases was observed for AmsI. AmsA shows characteristic motifs for membrane association and ATP binding. AmsF carries a secretory signal sequence in the N-terminus and could be involved in periplasmic processing of the repeating units. Complementation experiments located a promoter region required for gene expression as far as 500 bp upstream of amsG. It is preceded by a typical transcriptional termination sequence. A mutation upstream of the terminator did not affect amylovoran synthesis. Partial nucleotide sequences further upstream of the ams region showed homology to genes mapped at 45 min on the Escherichia coli chromosome. A termination sequence was also found downstream of the ams operon at a distance of 16 kb from the promoter. Between amsF and this terminator, three additional ORFs were detected.
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Affiliation(s)
- P Bugert
- Max-Planck-Institut für medizinische Forschung, Heidelberg, Germany
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Ivashina TV, Khmelnitsky MI, Shlyapnikov MG, Kanapin AA, Ksenzenko VN. The pss4 gene from Rhizobium leguminosarum by viciae VF39: cloning, sequence and the possible role in polysaccharide production and nodule formation. Gene X 1994; 150:111-6. [PMID: 7959035 DOI: 10.1016/0378-1119(94)90868-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The Tn5 insertion into the genome of Rhizobium leguminosarum bv viciae VF39, resulting in non-mucoid growth and formation of non-N2-fixing nodule-like structures on Vicia faba plants, was mapped within a 1.4-kb EcoRV-SacI fragment. Nucleotide sequence analysis revealed an ORF (pss4) of 263 amino acids (aa). Three transcription start points (tsp) were determined. Two of them were localized upstream from the first GTG codon; the third tsp was mapped in front of the second putative start codon (GTG) corresponding to Val64 of the Pss4 aa sequence. The expression of pss4 in a T7 RNA polymerase/promoter system produced a single approx. 29-kDa protein. Pss4 reveals similarity to several proteins involved in polysaccharide biosynthesis in various Rhizobium species. A nearly complete homology was found with PssA from Rl biovar phaseoli 8002 [Borthakur et al., Mol. Gen. Genet. 213 (1988) 155-162], except that Pss4 has an additional 63 aa on its N terminus.
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MESH Headings
- Amino Acid Sequence
- Bacterial Proteins/genetics
- Base Sequence
- Cloning, Molecular
- DNA Transposable Elements/genetics
- DNA, Bacterial
- Fabaceae/microbiology
- Genes, Bacterial
- Membrane Proteins/genetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Plants, Medicinal
- Polysaccharides, Bacterial/biosynthesis
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- Regulatory Sequences, Nucleic Acid
- Rhizobium leguminosarum/genetics
- Rhizobium leguminosarum/physiology
- Sequence Homology, Amino Acid
- Symbiosis
- Transcription, Genetic
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Affiliation(s)
- T V Ivashina
- Institute of Biochemistry and Physiology of Microorganisms, Academy of Sciences, Pushchino, Moscow Region, Russia
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Guidolin A, Morona JK, Morona R, Hansman D, Paton JC. Nucleotide sequence analysis of genes essential for capsular polysaccharide biosynthesis in Streptococcus pneumoniae type 19F. Infect Immun 1994; 62:5384-96. [PMID: 7960118 PMCID: PMC303279 DOI: 10.1128/iai.62.12.5384-5396.1994] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Previous studies have shown that the capsular polysaccharide synthesis (cps) locus of the type 19F Streptococcus pneumoniae strain SSZ was closely linked to a copy of the insertion sequence IS1202 (J.K. Morona, A. Guidolin, R. Morona, D. Hansman, and J.C. Paton, J. Bacteriol. 176:4437-4443, 1994). In the present study, we used plasmid insertion and rescue and inverse PCR to clone 6,322 bp of flanking DNA upstream of IS1202. Sequence analysis indicated that this region contains six complete open reading frames (ORFs) and one partial ORF that are arranged as a single transcriptional unit. Chromosomal disruption of any of these ORFs in a smooth-type 19F strain leads to a rough (unencapsulated) phenotype, indicating that this operon is essential for capsule production. The ORFs have therefore been designated cps19fA to cps19fG, where cps19fA is the first gene of the type 19F cps locus. Furthermore, many of the gene products from this incomplete operon exhibit strong similarities to proteins known to be involved in the production of capsular polysaccharide, exopolysaccharide, teichoic acid, enterobacterial common antigen, and lipopolysaccharide from numerous other bacterial species. This has allowed us to propose functions for many of the type 19F cps gene products. Southern hybridization studies reveal that cps19fA and cps19fB are conserved among all 12 pneumococcal serotypes tested, whereas genes downstream of cps19fB are conserved among some, but not all, of the serotypes tested.
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Affiliation(s)
- A Guidolin
- Department of Microbiology, Women's and Children's Hospital, North Adelaide, Australia
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Griffin AM, Morris VJ, Gasson MJ. Genetic analysis of the acetan biosynthetic pathway in Acetobacter xylinum. Int J Biol Macromol 1994; 16:287-9. [PMID: 7727341 DOI: 10.1016/0141-8130(94)90057-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have identified, cloned and sequenced an 8422 base pair fragment of Acetobacter xylinum genomic DNA containing part of the acetan biosynthetic gene cluster. Computer analysis of the nucleotide sequence data generated revealed the presence of six open reading frames. Comparison of the translated sequences of putative genes to the amino acid sequences of genes from other organisms was used to assign functions to the aceA, aceC and manB genes. These genes were predicted to encode a UDP-glycosyl transferase, a GDP-mannosyl transferase and a phosphomannose isomerase/GDP-mannose pyrophosphorylase, respectively.
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Affiliation(s)
- A M Griffin
- Institute of Food Research, Norwich Laboratory, Colney, UK
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Pollock TJ, Thorne L, Yamazaki M, Mikolajczak MJ, Armentrout RW. Mechanism of bacitracin resistance in gram-negative bacteria that synthesize exopolysaccharides. J Bacteriol 1994; 176:6229-37. [PMID: 7928993 PMCID: PMC196963 DOI: 10.1128/jb.176.20.6229-6237.1994] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Four representative species from three genera of gram-negative bacteria that secrete exopolysaccharides acquired resistance to the antibiotic bacitracin by stopping synthesis of the exopolysaccharide. Xanthomonas campestris, Sphingomonas strains S-88 and NW11, and Escherichia coli K-12 secrete xanthan gum, sphingans S-88 and NW11, and colanic acid, respectively. The gumD gene in X. campestris is required to attach glucose-P to C55-isoprenyl phosphate, the first step in the assembly of xanthan. A recombinant plasmid carrying the gumD gene of X. campestris restored polysaccharide synthesis to bacitracin-resistant exopolysaccharide-negative mutants of X. campestris and Sphingomonas strains. Similarly, a newly cloned gene (spsB) from strain S-88 restored xanthan synthesis to the same X. campestris mutants. However, the intergeneric complementation did not extend to mutants of E. coli that were both resistant to bacitracin and nonproducers of colanic acid. The genetic results also suggest mechanisms for assembling the sphingans which have commercial potential as gelling and viscosifying agents.
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Wang L, Reeves PR. Involvement of the galactosyl-1-phosphate transferase encoded by the Salmonella enterica rfbP gene in O-antigen subunit processing. J Bacteriol 1994; 176:4348-56. [PMID: 7517393 PMCID: PMC205648 DOI: 10.1128/jb.176.14.4348-4356.1994] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
rfbT of Salmonella enterica LT2 was previously thought, together with rfaL, to be involved in the ligation of polymerized O antigen to core-lipid A, and three mutants were known. We report the mapping of the mutations to rfbP, the galactosyl-1-phosphate transferase gene, which is now shown to encode a bifunctional protein. The mutations which have the former rfbT phenotype are referred to as rfbP(T). We also show that rfbP(T) mutants are not blocked in the ligation step as previously believed but in an earlier step, possibly in flipping the O-antigen subunit on undecaprenyl pyrophosphate from the cytoplasmic to periplasmic face of the cytoplasmic membrane.
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Affiliation(s)
- L Wang
- Department of Microbiology, University of Sydney, New South Wales, Australia
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Bugg TD, Brandish PE. From peptidoglycan to glycoproteins: common features of lipid-linked oligosaccharide biosynthesis. FEMS Microbiol Lett 1994; 119:255-62. [PMID: 8050708 DOI: 10.1111/j.1574-6968.1994.tb06898.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The peptidoglycan layer of bacterial cell walls is biosynthesised using a lipid carrier undecaprenyl phosphate to assemble and transport the MurNAc(GlcNAc)-pentapeptide precursor. Similar lipid-linked cycles are involved in the biosynthesis of other bacterial exopolysaccharides and eukaryotic asparagine-linked glycoproteins, the latter involving the structurally related dolichyl phosphate as a lipid carrier. Recent protein sequence data and common inhibitors of the bacterial and eukaryotic systems have revealed functional similarities between the two systems. Biological and physical studies on the lipid carriers themselves have provided clues to their role in oligosaccharide translocation, but have not revealed significant differences in function between undecaprenyl phosphate and dolichyl phosphate. The presence of dolichyl phosphate and a family of saturated isoprenoid lipids in Archaebacteria suggests a possible evolutionary link between the two systems.
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Affiliation(s)
- T D Bugg
- Department of Chemistry, University of Southampton, Highfield, UK
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