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Bélanger L, Dimmick KA, Fleming JS, Charles TC. Null mutations in Sinorhizobium meliloti exoS and chvI demonstrate the importance of this two-component regulatory system for symbiosis. Mol Microbiol 2009; 74:1223-37. [PMID: 19843226 DOI: 10.1111/j.1365-2958.2009.06931.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Exopolysaccharides, either succinoglycan or galactoglucan, are essential for the establishment of the symbiosis between Sinorhizobium meliloti and Medicago sativa (alfalfa). The ExoS/ChvI two-component regulatory system is known as a regulator of succinoglycan production but the genes that are directly regulated by ChvI have not been determined. Difficulty isolating exoS and chvI null mutants has prompted the suggestion that these genes are essential for S. meliloti viability. We have successfully isolated exoS and chvI null mutants using a merodiploid-facilitated strategy. We present evidence that the S. meliloti ExoS/ChvI two-component regulatory system is essential for symbiosis with alfalfa. Phenotypic analyses of exoS and chvI null mutant strains demonstrate that ExoS/ChvI controls both succinoglycan and galactoglucan production and is required for growth on over 21 different carbon sources. These new findings suggest that the ExoS/ChvI regulatory targets might not be the exo genes that are specific for succinoglycan biosynthesis but rather genes that have common influence on both succinoglycan and galactoglucan production. Other studied alpha-proteobacteria ExoS/ChvI orthologues are required for the bacteria to invade or persist in host cells and thus we present more evidence that this two-component regulatory system is essential for alpha-proteobacterial host interaction.
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Affiliation(s)
- Louise Bélanger
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
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52
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The Sinorhizobium meliloti LpxXL and AcpXL proteins play important roles in bacteroid development within alfalfa. J Bacteriol 2009; 191:4681-6. [PMID: 19429615 DOI: 10.1128/jb.00318-09] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Free-living Sinorhizobium meliloti lpxXL and acpXL mutants lack lipid A very-long-chain fatty acids (VLCFAs) and have reduced competitiveness in alfalfa. We demonstrate that LpxXL and AcpXL play important but distinct roles in bacteroid development and that LpxXL is essential for the modification of S. meliloti bacteroid lipid A with VLCFAs.
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Abstract
The ExpR/Sin quorum-sensing system of the gram-negative soil bacterium Sinorhizobium meliloti plays an important role in the establishment of symbiosis with its host plant Medicago sativa. A mutant unable to produce autoinducer signal molecules (sinI) is deficient in its ability to invade the host, but paradoxically, a strain lacking the quorum-sensing transcriptional regulator ExpR is as efficient as the wild type. We compared the whole-genome expression profile of the wild-type strain with strains missing one of the quorum-sensing regulatory components to identify genes controlled by the ExpR/Sin system throughout the different phases of the bacterial growth cycle, as well as in planta. Our analyses revealed that ExpR is a highly versatile regulator with a unique ability to show different regulatory capabilities in the presence or absence of an autoinducer. In addition, this study provided us with insight into the plant invasion defect displayed by the autoinducer mutant. We also discovered that the ExpR/Sin quorum-sensing system is repressed after plant invasion. Therefore, quorum sensing plays a crucial role in the regulation of many cell functions that ensures the successful invasion of the host and is inactivated once symbiosis is established.
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54
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Tan XJ, Cheng Y, Li YX, Li YG, Zhou JC. BacA is indispensable for successful Mesorhizobium–Astragalus symbiosis. Appl Microbiol Biotechnol 2009; 84:519-26. [DOI: 10.1007/s00253-009-1959-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 03/08/2009] [Accepted: 03/10/2009] [Indexed: 11/29/2022]
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Domenech P, Kobayashi H, LeVier K, Walker GC, Barry CE. BacA, an ABC transporter involved in maintenance of chronic murine infections with Mycobacterium tuberculosis. J Bacteriol 2009; 191:477-85. [PMID: 18996991 PMCID: PMC2620812 DOI: 10.1128/jb.01132-08] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Accepted: 10/31/2008] [Indexed: 11/20/2022] Open
Abstract
BacA is an inner membrane protein associated with maintenance of chronic infections in several diverse host-pathogen interactions. To understand the function of the bacA gene in Mycobacterium tuberculosis (Rv1819c), we insertionally inactivated this gene and analyzed the resulting mutant for a variety of phenotypes. BacA deficiency in M. tuberculosis did not affect sensitivity to detergents, acidic pH, and zinc, indicating that there was no global compromise in membrane integrity, and a comprehensive evaluation of the major lipid constituents of the cell envelope failed to reveal any significant differences. Infection of mice with this mutant revealed no impact on establishment of infection but a profound effect on maintenance of extended chronic infection and ultimate outcome. As in alphaproteobacteria, deletion of BacA in M. tuberculosis led to increased bleomycin resistance, and heterologous expression of the M. tuberculosis BacA homolog in Escherichia coli conferred sensitivity to antimicrobial peptides. These results suggest a striking conservation of function for BacA-related proteins in transport of a critical molecule that determines the outcome of the host-pathogen interaction.
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Affiliation(s)
- Pilar Domenech
- Tuberculosis Research Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Disease, 33 North Drive, Bethesda, Maryland 20892, USA
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56
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Ramos-Vega AL, Dávila-Martínez Y, Sohlenkamp C, Contreras-Martínez S, Encarnación S, Geiger O, López-Lara IM. SMb20651 is another acyl carrier protein from Sinorhizobium meliloti. Microbiology (Reading) 2009; 155:257-267. [DOI: 10.1099/mic.0.022079-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Acyl carrier proteins (ACPs) are small acidic proteins that carry growing acyl chains during fatty acid or polyketide synthesis. In rhizobia, there are four different and well-characterized ACPs: AcpP, NodF, AcpXL and RkpF. The genome sequence ofSinorhizobium meliloti1021 reveals two additional ORFs that possibly encode additional ACPs. One of these,smb20651, is located on the plasmid pSymB as part of an operon. The genes of the operon encode a putative asparagine synthetase (AsnB), the predicted ACP (SMb20651), a putative long-chain fatty acyl-CoA ligase (SMb20650) and a putative ammonium-dependent NAD+synthetase (NadE1). When SMb20651 was overexpressed inEscherichia coli,[3H]β-alanine, a biosynthetic building block of 4′-phosphopantetheine, was incorporated into the proteinin vivo. The purified SMb20651 was modified with 4′-phosphopantetheine in the presence ofS. melilotiholo-ACP synthase (AcpS). Also, holo-SMb20651 was modifiedin vitrowith a malonyl group by malonyl CoA-ACP transacylase. InE. coli, coexpression of SMb20651 together with other proteins such as AcpS and SMb20650 led to the formation of additional forms of SMb20651. In this bacterium, acylation of SMb20651 with C12 : 0 or C18 : 0 fatty acids was detected, demonstrating that this protein is involved in fatty acid biosynthesis or transfer. Expression of SMb20651 was detected inS. melilotias holo-SMb20651 and acyl-SMb20651.
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Affiliation(s)
- Ana Laura Ramos-Vega
- Programa de Ecología Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
| | - Yadira Dávila-Martínez
- Programa de Ecología Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
| | - Christian Sohlenkamp
- Programa de Ecología Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
| | - Sandra Contreras-Martínez
- Programa de Genómica Funcional de Procariontes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
| | - Sergio Encarnación
- Programa de Genómica Funcional de Procariontes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
| | - Otto Geiger
- Programa de Ecología Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
| | - Isabel M. López-Lara
- Programa de Ecología Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos C. P. 62251, Mexico
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57
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Essential role for the BacA protein in the uptake of a truncated eukaryotic peptide in Sinorhizobium meliloti. J Bacteriol 2008; 191:1519-27. [PMID: 19074376 DOI: 10.1128/jb.01661-08] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The inner membrane BacA protein is essential for the establishment of chronic intracellular infections by Sinorhizobium meliloti and Brucella abortus within plant and mammalian hosts, respectively. In their free-living state, S. meliloti and B. abortus mutants lacking BacA have reductions in their outer membrane lipid A very-long-chain fatty acid (VLCFA) contents and exhibit low-level resistance to the glycopeptide bleomycin in comparison to their respective parent strains. In this paper we investigate the hypothesis that BacA is involved in peptide uptake in S. meliloti. We determined that an S. meliloti DeltabacA mutant is completely resistant to a truncated form of the eukaryotic peptide Bac7, Bac7(1-16), and this phenotype appears to be independent of its lipid A alteration. Subsequently, we discovered that BacA and/or Escherichia coli SbmA is essential for fluorescently labeled Bac7(1-16) uptake in S. meliloti. Given that there are hundreds of root nodule-specific peptides within the legume host, our data suggest that BacA-mediated peptide uptake could play a central role in the chronic infection process of S. meliloti. However, since we determined that two symbiotically defective S. meliloti bacA site-directed mutants (with the Q193G and R389G mutations, respectively) with known reductions in their lipid A VLCFA contents are still capable of peptide uptake, these findings suggest that BacA-dependent peptide uptake cannot fully account for the essential role of BacA in the legume symbiosis. Further, they provide evidence that the BacA function that leads to the S. meliloti lipid A VLCFA modification plays a key role in the chronic infection of legumes.
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58
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Beck S, Marlow VL, Woodall K, Doerrler WT, James EK, Ferguson GP. The Sinorhizobium meliloti MsbA2 protein is essential for the legume symbiosis. MICROBIOLOGY-SGM 2008; 154:1258-1270. [PMID: 18375818 DOI: 10.1099/mic.0.2007/014894-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Sinorhizobium meliloti is a beneficial legume symbiont, closely related to Brucella species, which are chronic mammalian pathogens. We discovered that the S. meliloti MsbA2 protein is essential to ensure the symbiotic interaction with the host plant, alfalfa. S. meliloti invades plant cells via plant-derived structures known as infection threads. However, in the absence of MsbA2, S. meliloti remains trapped within abnormally thickened infection threads and induces a heightened plant defence response, characterized by a substantial thickening of the nodule endodermis layer and the accumulation of polyphenolic compounds. The S. meliloti MsbA2 protein is homologous to the Escherichia coli lipopolysaccharide/phospholipid trafficking protein MsbA. However, MsbA2 was not essential for the membrane transport of either lipopolysaccharide or phospholipids in S. meliloti. We determined that the msbA2 gene is transcribed in free-living S. meliloti and that in the absence of MsbA2 the polysaccharide content of S. meliloti is altered. Consequently, we propose a model whereby the altered polysaccharide content of the S. meliloti msbA2 mutant could be responsible for its symbiotic defect by inducing an inappropriate host response.
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Affiliation(s)
- Sebastian Beck
- Institute of Cell Biology and Centre for Science at Extreme Conditions, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - Victoria L Marlow
- School of Medicine, Department of Medicine and Therapeutics, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.,Institute of Cell Biology and Centre for Science at Extreme Conditions, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - Katy Woodall
- Institute of Cell Biology and Centre for Science at Extreme Conditions, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh EH9 3JR, UK
| | - William T Doerrler
- Department of Biological Sciences, Louisiana State University, 202 Life Sciences Building, Baton Rouge, LA 70803, USA
| | - Euan K James
- College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Gail P Ferguson
- School of Medicine, Department of Medicine and Therapeutics, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.,Institute of Cell Biology and Centre for Science at Extreme Conditions, School of Biological Sciences, King's Buildings, University of Edinburgh, Edinburgh EH9 3JR, UK
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59
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Abstract
Rhizobial bacteria colonize legume roots for the purpose of biological nitrogen fixation. A complex series of events, coordinated by host and bacterial signal molecules, underlie the development of this symbiotic interaction. Rhizobia elicit de novo formation of a novel root organ within which they establish a chronic intracellular infection. Legumes permit rhizobia to invade these root tissues while exerting control over the infection process. Once rhizobia gain intracellular access to their host, legumes also strongly influence the process of bacterial differentiation that is required for nitrogen fixation. Even so, symbiotic rhizobia play an active role in promoting their goal of host invasion and chronic persistence by producing a variety of signal molecules that elicit changes in host gene expression. In particular, rhizobia appear to advocate for their access to the host by producing a variety of signal molecules capable of suppressing a general pathogen defense response.
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Affiliation(s)
- Katherine E. Gibson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Hajime Kobayashi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Graham C. Walker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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60
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A highly conserved protein of unknown function is required by Sinorhizobium meliloti for symbiosis and environmental stress protection. J Bacteriol 2007; 190:1118-23. [PMID: 18055601 DOI: 10.1128/jb.01521-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We report here the first characterization of the Sinorhizobium meliloti open reading frame SMc01113. The SMc01113 protein is a member of a highly conserved protein family, universal among bacteria. We demonstrate that the SMc01113 gene is absolutely required for S. meliloti symbiosis with alfalfa and also for the protection of the bacterium from a wide range of environmental stresses.
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61
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Mattiuzzo M, Bandiera A, Gennaro R, Benincasa M, Pacor S, Antcheva N, Scocchi M. Role of the Escherichia coli SbmA in the antimicrobial activity of proline-rich peptides. Mol Microbiol 2007; 66:151-63. [PMID: 17725560 DOI: 10.1111/j.1365-2958.2007.05903.x] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In contrast to many antimicrobial peptides, members of the proline-rich group of antimicrobial peptides inactivate Gram-negative bacteria by a non-lytic mechanism. Several lines of evidence indicate that they are internalized into bacteria and their activity mediated by interaction with unknown cellular components. With the aim of identifying such interactors, we selected mutagenized Escherichia coli clones resistant to the proline-rich Bac7(1-35) peptide and analysed genes responsible for conferring resistance, whose products may thus be involved in the peptide's mode of action. We isolated a number of genomic regions bearing such genes, and one in particular coding for SbmA, an inner membrane protein predicted to be part of an ABC transporter. An E. coli strain carrying a point mutation in sbmA, as well as other sbmA-null mutants, in fact showed resistance to several proline-rich peptides but not to representative membranolytic peptides. Use of fluorescently labelled Bac7(1-35) confirmed that resistance correlated with a decreased ability to internalize the peptide, suggesting that a bacterial protein, SbmA, is necessary for the transport of, and for susceptibility to, proline-rich antimicrobial peptides of eukaryotic origin.
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Affiliation(s)
- Maura Mattiuzzo
- Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, Via Giorgieri 1, 34127 Trieste, Italy
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62
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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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63
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Ferguson GP, Jansen A, Marlow VL, Walker GC. BacA-mediated bleomycin sensitivity in Sinorhizobium meliloti is independent of the unusual lipid A modification. J Bacteriol 2006; 188:3143-8. [PMID: 16585777 PMCID: PMC1447001 DOI: 10.1128/jb.188.8.3143-3148.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sinorhizobium meliloti bacA mutants are symbiotically defective, deoxycholate sensitive, and bleomycin resistant. We show that the bleomycin resistance phenotype is independent of the lipid A alteration and that the changes giving rise to both phenotypes are likely to be involved in the inability of bacA mutants to persist within their hosts.
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Affiliation(s)
- Gail P Ferguson
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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64
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Vedam V, Kannenberg E, Datta A, Brown D, Haynes-Gann JG, Sherrier DJ, Carlson RW. The pea nodule environment restores the ability of a Rhizobium leguminosarum lipopolysaccharide acpXL mutant to add 27-hydroxyoctacosanoic acid to its lipid A. J Bacteriol 2006; 188:2126-33. [PMID: 16513742 PMCID: PMC1428142 DOI: 10.1128/jb.188.6.2126-2133.2006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 12/22/2005] [Indexed: 11/20/2022] Open
Abstract
Members of the Rhizobiaceae contain 27-hydroxyoctacosanoic acid (27OHC(28:0)) in their lipid A. A Rhizobium leguminosarum 3841 acpXL mutant (named here Rlv22) lacking a functional specialized acyl carrier lacked 27OHC(28:0) in its lipid A, had altered growth and physiological properties (e.g., it was unable to grow in the presence of an elevated salt concentration [0.5% NaCl]), and formed irregularly shaped bacteroids, and the synchronous division of this mutant and the host plant-derived symbiosome membrane was disrupted. In spite of these defects, the mutant was able to persist within the root nodule cells and eventually form, albeit inefficiently, nitrogen-fixing bacteroids. This result suggested that while it is in a host root nodule, the mutant may have some mechanism by which it adapts to the loss of 27OHC(28:0) from its lipid A. In order to further define the function of this fatty acyl residue, it was necessary to examine the lipid A isolated from mutant bacteroids. In this report we show that addition of 27OHC(28:0) to the lipid A of Rlv22 lipopolysaccharides is partially restored in Rlv22 acpXL mutant bacteroids. We hypothesize that R. leguminosarum bv. viciae 3841 contains an alternate mechanism (e.g., another acp gene) for the synthesis of 27OHC(28:0), which is activated when the bacteria are in the nodule environment, and that it is this alternative mechanism which functionally replaces acpXL and is responsible for the synthesis of 27OHC(28:0)-containing lipid A in the Rlv22 acpXL bacteroids.
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Affiliation(s)
- Vinata Vedam
- University of Georgia, Complex Carbohydrate Research Center, 315 Riverbend Rd., Athens, GA 30602, USA
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65
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Carle A, Höppner C, Ahmed Aly K, Yuan Q, den Dulk-Ras A, Vergunst A, O'Callaghan D, Baron C. The Brucella suis type IV secretion system assembles in the cell envelope of the heterologous host Agrobacterium tumefaciens and increases IncQ plasmid pLS1 recipient competence. Infect Immun 2006; 74:108-17. [PMID: 16368963 PMCID: PMC1346655 DOI: 10.1128/iai.74.1.108-117.2006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pathogenic Brucella species replicate within mammalian cells, and their type IV secretion system is essential for intracellular survival and replication. The options for biochemical studies on the Brucella secretion system are limited due to the rigidity of the cells and biosafety concerns, which preclude large-scale cell culture and fractionation. To overcome these problems, we heterologously expressed the Brucella suis virB operon in the closely related alpha(2)-proteobacterium Agrobacterium tumefaciens and showed that the VirB proteins assembled into a complex. Eight of the twelve VirB proteins were detected in the membranes of the heterologous host with specific antisera. Cross-linking indicated protein-protein interactions similar to those in other type IV secretion systems, and the results of immunofluorescence analysis supported the formation of VirB protein complexes in the cell envelope. Production of a subset of the B. suis VirB proteins (VirB3-VirB12) in A. tumefaciens strongly increased its ability to receive IncQ plasmid pLS1 in conjugation experiments, and production of VirB1 further enhanced the conjugation efficiency. Plasmid recipient competence correlated with periplasmic leakage and the detergent sensitivity of A. tumefaciens, suggesting a weakening of the cell envelope. Heterologous expression thus permits biochemical characterization of B. suis type IV secretion system assembly.
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Affiliation(s)
- Anna Carle
- McMaster University, Department of Biology, 1280 Main Street West, Hamilton, Ontario LS8 4K1, Canada
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66
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Ferguson GP, Datta A, Carlson RW, Walker GC. Importance of unusually modified lipid A in Sinorhizobium stress resistance and legume symbiosis. Mol Microbiol 2005; 56:68-80. [PMID: 15773979 DOI: 10.1111/j.1365-2958.2005.04536.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sinorhizobium meliloti, a legume symbiont and Brucella abortus, a phylogenetically related mammalian pathogen, both require their BacA proteins to establish chronic intracellular infections in their respective hosts. The lipid A molecules of S. meliloti and B. abortus are unusually modified with a very-long-chain fatty acid (VLCFA; C > or = 28) and we discovered that BacA is involved in this unusual modification. This observation raised the possibility that the unusual lipid A modification could be crucial for the chronic infection of both S. meliloti and B. abortus. We investigated this by constructing and characterizing S. meliloti mutants in the lpxXL and acpXL genes, which encode an acyl transferase and acyl carrier protein directly involved in the biosynthesis of VLCFA-modified lipid A. Our analysis revealed that the unusually modified lipid A is important, but not crucial, for S. meliloti chronic infection and that BacA must have an additional function, which in combination with its observed effect on the lipid A in the free-living form of S. meliloti, is essential for the chronic infection. Additionally, we discovered that in the absence of VLCFAs, S. meliloti produces novel pentaacylated lipid A species, modified with unhydroxylated fatty acids, which are important for stress resistance.
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Affiliation(s)
- Gail P Ferguson
- Institute of Structural and Molecular Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JR, UK.
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67
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Jensen JB, Ampomah OY, Darrah R, Peters NK, Bhuvaneswari TV. Role of trehalose transport and utilization in Sinorhizobium meliloti--alfalfa interactions. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:694-702. [PMID: 16042015 DOI: 10.1094/mpmi-18-0694] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Genes thuA and thuB in Sinorhizobium meliloti Rm1021 code for a major pathway for trehalose catabolism and are induced by trehalose but not by related structurally similar disaccharides like sucrose or maltose. S. meliloti strains mutated in either of these two genes were severely impaired in their ability to grow on trehalose as the sole source of carbon. ThuA and ThuB show no homology to any known enzymes in trehalose utilization. ThuA has similarity to proteins of unknown function in Mesorhizobium loti, Agrobacterium tumefaciens, and Brucella melitensis, and ThuB possesses homology to dehydrogenases containing the consensus motif AGKHVXCEKP. thuAB genes are expressed in bacteria growing on the root surface and in the infection threads but not in the symbiotic zone of the nodules. Even though thuA and thuB mutants were impaired in competitive colonization of Medicago sativa roots, these strains were more competitive than the wild-type Rml021 in infecting alfalfa roots and forming nitrogen-fixing nodules. Possible reasons for their increased competitiveness are discussed.
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Affiliation(s)
- John Beck Jensen
- Department of Biology, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
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Li G, Laturnus C, Ewers C, Wieler LH. Identification of genes required for avian Escherichia coli septicemia by signature-tagged mutagenesis. Infect Immun 2005; 73:2818-27. [PMID: 15845486 PMCID: PMC1087346 DOI: 10.1128/iai.73.5.2818-2827.2005] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infections with avian pathogenic Escherichia coli (APEC) cause colibacillosis, an acute and largely systemic disease resulting in significant economic losses in poultry industry worldwide. Although various virulence-associated genes have been identified in APEC, their actual role in pathogenesis is still not fully understood, and, furthermore, certain steps of the infection process have not been related to previously identified factors. Here we describe the application of a signature-tagged transposon mutagenesis (STM) approach to identify critical genes required for APEC infections in vivo. Twenty pools of about 1,800 IMT5155 (O2:H5) mutants were screened in an infection model using 5-week-old chickens, and potentially attenuated mutants were subjected to a secondary screen and in vivo competition assays to confirm their attenuation. A total of 28 genes required for E. coli septicemia in chickens were identified as candidates for further characterization. Among these disrupted genes, six encode proteins involved in biosynthesis of extracellular polysaccharides and lipopolysaccharides; two encode iron transporters that have not been previously characterized in APEC in in vivo studies, and four showed similarity to membrane or periplasmic proteins. In addition, several metabolic enzymes, putative proteins with unknown function, and open reading frames with no similarity to other database entries were identified. This genome-wide analysis has identified both novel and previously known factors potentially involved in pathogenesis of APEC infection.
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Affiliation(s)
- Ganwu Li
- Institute of Microbiology and Epizootics, Free University Berlin, P.O. Box 040225, Philippstrasse 13, D-10115 Berlin, Germany
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69
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Identification of genes required for avian Escherichia coli septicemia by signature-tagged mutagenesis. Infect Immun 2005. [PMID: 15845486 DOI: 10.1128/iai.73.5.2818–2827.2005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Infections with avian pathogenic Escherichia coli (APEC) cause colibacillosis, an acute and largely systemic disease resulting in significant economic losses in poultry industry worldwide. Although various virulence-associated genes have been identified in APEC, their actual role in pathogenesis is still not fully understood, and, furthermore, certain steps of the infection process have not been related to previously identified factors. Here we describe the application of a signature-tagged transposon mutagenesis (STM) approach to identify critical genes required for APEC infections in vivo. Twenty pools of about 1,800 IMT5155 (O2:H5) mutants were screened in an infection model using 5-week-old chickens, and potentially attenuated mutants were subjected to a secondary screen and in vivo competition assays to confirm their attenuation. A total of 28 genes required for E. coli septicemia in chickens were identified as candidates for further characterization. Among these disrupted genes, six encode proteins involved in biosynthesis of extracellular polysaccharides and lipopolysaccharides; two encode iron transporters that have not been previously characterized in APEC in in vivo studies, and four showed similarity to membrane or periplasmic proteins. In addition, several metabolic enzymes, putative proteins with unknown function, and open reading frames with no similarity to other database entries were identified. This genome-wide analysis has identified both novel and previously known factors potentially involved in pathogenesis of APEC infection.
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70
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Brewin NJ. Plant Cell Wall Remodelling in the Rhizobium–Legume Symbiosis. CRITICAL REVIEWS IN PLANT SCIENCES 2004; 23:293-316. [PMID: 0 DOI: 10.1080/07352680490480734] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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71
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Ferguson GP, Datta A, Baumgartner J, Roop RM, Carlson RW, Walker GC. Similarity to peroxisomal-membrane protein family reveals that Sinorhizobium and Brucella BacA affect lipid-A fatty acids. Proc Natl Acad Sci U S A 2004; 101:5012-7. [PMID: 15044696 PMCID: PMC387365 DOI: 10.1073/pnas.0307137101] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sinorhizobium meliloti, a legume symbiont, and Brucella abortus, a phylogenetically related mammalian pathogen, both require the bacterial-encoded BacA protein to establish chronic intracellular infections in their respective hosts. We found that the bacterial BacA proteins share sequence similarity with a family of eukaryotic peroxisomal-membrane proteins, including the human adrenoleukodystrophy protein, required for the efficient transport of very-long-chain fatty acids out of the cytoplasm. This insight, along with the increased sensitivity of BacA-deficient mutants to detergents and cell envelope-disrupting agents, led us to discover that BacA affects the very-long-chain fatty acid (27-OHC28:0 and 29-OHC30:0) content of both Sinorhizobium and Brucella lipid A. We discuss models for how BacA function affects the lipid-A fatty-acid content and why this activity could be important for the establishment of chronic intracellular infections.
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Affiliation(s)
- Gail P Ferguson
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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72
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Mitsui H, Sato T, Sato Y, Ito N, Minamisawa K. Sinorhizobium meliloti RpoH1 is required for effective nitrogen-fixing symbiosis with alfalfa. Mol Genet Genomics 2004; 271:416-25. [PMID: 15007732 DOI: 10.1007/s00438-004-0992-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2003] [Accepted: 02/10/2004] [Indexed: 11/29/2022]
Abstract
Sinorhizobium meliloti is a root-nodulating, nitrogen-fixing bacterium. An S. meliloti strain that is mutant for the rpoH(1) gene, which encodes a sigma(32)-like protein, elicits the formation of ineffective nodules on the host plant alfalfa. We characterized the rpoH(1) mutant for phenotypes related to symbiosis. Alfalfa nodules formed by the rpoH(1) mutant exhibited greatly reduced levels of acetylene reduction activity compared to the wild-type nodules. Whereas intracellular colonization by rhizobia was observed in a zone just below the apical meristem, we found ultrastructural abnormalities and signs of degeneration of bacteroids within many host cells in the proximally adjacent zone. In the proximal part of the nodule, only a few nodule cells contained bacteroids. In contrast, the rpoH(1) mutant showed normal induction of nitrogen fixation gene expression in microaerobic culture. These results suggest that the rpoH(1) mutation causes early senescence of bacteroids during the endosymbiotic process, but does not affect the invasion process or the synthesis of the nitrogenase machinery. The rpoH(1) mutant exhibited increased sensitivity to various agents and to acid pH, suggesting that RpoH(1) is required to protect the bacterial cell against environmental stresses encountered within the host. Since RpoH(1) was previously reported to be required for the synthesis of some heat shock proteins (Hsps), we examined the transcription of several genes for Hsp homologs. We found that transcription of groESL(5), lon, and clpB after heat shock was RpoH(1)-dependent, and conserved nucleotide sequences were found in the -35 and -10 regions upstream of the transcription start sites of these genes. Although groESL(5) expression is almost completely dependent on RpoH(1), we found that a groESL(5) mutant strain is still capable of normal symbiotic nitrogen fixation on alfalfa.
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Affiliation(s)
- H Mitsui
- Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, 980-8577 Sendai, Japan.
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73
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Kiss E, Huguet T, Poinsot V, Batut J. The typA gene is required for stress adaptation as well as for symbiosis of Sinorhizobium meliloti 1021 with certain Medicago truncatula lines. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:235-44. [PMID: 15000390 DOI: 10.1094/mpmi.2004.17.3.235] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In this article, we describe the typA gene of Sinorhizobium meliloti, the orthologue of typA/bipA genes found in a wide range of bacteria. We found that typA was required for survival of S. meliloti under certain stress conditions, such as growth at low temperature or low pH and in the presence of sodium dodecyl sulfate (SDS). The cold-sensitive phenotype of both Escherichia coli bipA and S. meliloti typA mutants were cross-complemented, indicating that the two genes are functionally equivalent. typA was indispensable for symbiosis on Medicago truncatula Jemalong and F83005.5 and contributes to the full efficiency of symbiosis on other host plant lines such as DZA315.16 or several cultivars of M. sativa. Hence, the symbiotic requirement for typA is host dependent. Interestingly, the symbiotic defect was different on Jemalong and F83005.5 plants, thus indicating that typA is required at a different stage of the symbiotic interaction.
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Affiliation(s)
- Ernö Kiss
- Laboratoire des Interactions Plantes Microorganismes, Centre National de la Recherche Scientifique (UMR 2594), Institut National de la Recherche Agronomique (UMR 441), BP27, 31326 Castanet, Tolosan cedex, France
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Patriarca EJ, Tatè R, Ferraioli S, Iaccarino M. Organogenesis of legume root nodules. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 234:201-62. [PMID: 15066376 DOI: 10.1016/s0074-7696(04)34005-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The N(2)-fixing nodules elicited by rhizobia on legume roots represent a useful model for studying plant development. Nodule formation implies a complex progression of temporally and spatially regulated events of cell differentiation/dedifferentiation involving several root tissues. In this review we describe the morphogenetic events leading to the development of these histologically well-structured organs. These events include (1) root hair deformation, (2) development and growth of infection threads, (3) induction of the nodule primordium, and (4) induction, activity, and persistence of the nodular meristem and/or of foci of meristematic activities. Particular attention is given to specific aspects of the symbiosis, such as the early stages of intracellular invasion and to differentiation of the intracellular form of rhizobia, called symbiosomes. These developmental aspects were correlated with (1) the regulatory signals exchanged, (2) the plant genes expressed in specific cell types, and (3) the staining procedures that allow the recognition of some cell types. When strictly linked with morphogenesis, the nodulation phenotypes of plant and bacterial mutants such as the developmental consequence of the treatment with metabolic inhibitors, metabolic intermediates, or the variation of physical parameters are described. Finally, some aspects of nodule senescence and of regulation of nodulation are discussed.
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Affiliation(s)
- Eduardo J Patriarca
- Institute of Genetics and Biophysics Adriano Buzzati-Traverso, Consiglio Nazionale delle Ricerche, 80125 Naples, Italy
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Rezuchova B, Miticka H, Homerova D, Roberts M, Kormanec J. New members of the Escherichia coli sigmaE regulon identified by a two-plasmid system. FEMS Microbiol Lett 2003; 225:1-7. [PMID: 12900013 DOI: 10.1016/s0378-1097(03)00480-4] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
A previously established method, based on a two-plasmid system, was used to identify promoters recognized by RNA polymerase containing the extracytoplasmic stress response sigma factor sigmaE in Escherichia coli. In addition to previously identified rpoE-dependent promoters, 11 new promoters potentially directing the expression of 15 genes were identified that were active only after over-expression of rpoE. The promoters were confirmed and transcriptional start points of the promoters were determined by primer extension analysis and S1-nuclease mapping. All the promoters contained sequences similar to the consensus sequence of rpoE-dependent promoters. The new rpoE-dependent promoters governed expression of genes encoding proteins involved in primary metabolism (fusA, tufA, recR), phospholipid and lipopolysaccharide biosynthesis (psd, lpxP), signal transduction (sixA), proposed inner or outer membrane proteins (bacA, sbmA, smpA, yeaY), and proteins with unknown function (ybaB, yaiW, yiiS, yiiT, yfeY).
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Affiliation(s)
- Bronislava Rezuchova
- Institute of Molecular Biology, Center of Excellence for Molecular Medicine, Slovak Academy of Science, Dubravska cesta 21, 845 51 Bratislava, Slovak Republic
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76
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Campbell GRO, Sharypova LA, Scheidle H, Jones KM, Niehaus K, Becker A, Walker GC. Striking complexity of lipopolysaccharide defects in a collection of Sinorhizobium meliloti mutants. J Bacteriol 2003; 185:3853-62. [PMID: 12813079 PMCID: PMC161594 DOI: 10.1128/jb.185.13.3853-3862.2003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the role that lipopolysaccharide (LPS) plays in the symbiosis between Sinorhizobium meliloti and alfalfa has been studied for over a decade, its function in this process remains controversial and poorly understood. This is largely due to a lack of mutants affected by its synthesis. In one of the definitive studies concerning this issue, Clover et al. (R. H. Clover, J. Kieber, and E. R. Signer, J. Bacteriol. 171:3961-3967, 1989) identified a series of mutants with putative LPS defects, judged them to be symbiotically proficient on Medicago sativa, and concluded that LPS might not have a symbiotic function in S. meliloti. The mutations in these strains were never characterized at the molecular level nor was the LPS from most of them analyzed. We have transduced these mutations from the Rm2011 background from which they were originally isolated into the sequenced strain Rm1021 and have characterized the resulting strains in greater detail. We found the LPS from these mutants to display a striking complexity of phenotypes on polyacrylamide electrophoresis gels, including additional rough LPS bands and alterations in the molecular weight distribution of the smooth LPS. We found that some of the mutants contain insertions in genes that are predicted to be involved in the synthesis of carbohydrate components of LPS, including ddhB, lpsB, lpsC, and lpsE. The majority, however, code for proteins predicted to be involved in a wide variety of functions not previously recognized to play a role in LPS synthesis, including a possible transcription elongation factor (GreA), a possible queuine synthesis protein, and a possible chemotaxis protein. Furthermore, using more extensive assays, we have found that most of these strains have symbiotic deficiencies. These results support more recent findings that alterations in LPS structure can affect the ability of S. meliloti to form an effective symbiosis.
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Affiliation(s)
- Gordon R O Campbell
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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77
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Ampe F, Kiss E, Sabourdy F, Batut J. Transcriptome analysis of Sinorhizobium meliloti during symbiosis. Genome Biol 2003; 4:R15. [PMID: 12620125 PMCID: PMC151305 DOI: 10.1186/gb-2003-4-2-r15] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2002] [Revised: 11/14/2002] [Accepted: 12/18/2002] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Rhizobia induce the formation on specific legumes of new organs, the root nodules, as a result of an elaborated developmental program involving the two partners. In order to contribute to a more global view of the genetics underlying this plant-microbe symbiosis, we have mined the recently determined Sinorhizobium meliloti genome sequence for genes potentially relevant to symbiosis. We describe here the construction and use of dedicated nylon macroarrays to study simultaneously the expression of 200 of these genes in a variety of environmental conditions, pertinent to symbiosis. RESULTS The expression of 214 S. meliloti genes was monitored under ten environmental conditions, including free-living aerobic and microaerobic conditions, addition of the plant symbiotic elicitor luteolin, and a variety of symbiotic conditions. Five new genes induced by luteolin have been identified as well as nine new genes induced in mature nitrogen-fixing bacteroids. A bacterial and a plant symbiotic mutant affected in nodule development have been found of particular interest to decipher gene expression at the intermediate stage of the symbiotic interaction. S. meliloti gene expression in the cultivated legume Medicago sativa (alfalfa) and the model plant M. truncatula were compared and a small number of differences was found. CONCLUSIONS In addition to exploring conditions for a genome-wide transcriptome analysis of the model rhizobium S. meliloti, the present work has highlighted the differential expression of several classes of genes during symbiosis. These genes are related to invasion, oxidative stress protection, iron mobilization, and signaling, thus emphasizing possible common mechanisms between symbiosis and pathogenesis.
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Affiliation(s)
- Frederic Ampe
- Address: Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, UMR 215 Centre National de la Recherche Scientifique - Institut National de la Recherche Agronomique, BP27-31326 Castanet-Tolosan cedex, France
| | - Ernö Kiss
- Address: Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, UMR 215 Centre National de la Recherche Scientifique - Institut National de la Recherche Agronomique, BP27-31326 Castanet-Tolosan cedex, France
| | - Frédérique Sabourdy
- Address: Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, UMR 215 Centre National de la Recherche Scientifique - Institut National de la Recherche Agronomique, BP27-31326 Castanet-Tolosan cedex, France
| | - Jacques Batut
- Address: Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, UMR 215 Centre National de la Recherche Scientifique - Institut National de la Recherche Agronomique, BP27-31326 Castanet-Tolosan cedex, France
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