scholarly journals Role of Trehalose Transport and Utilization in Sinorhizobium meliloti-Alfalfa Interactions

2005 ◽  
Vol 18 (7) ◽  
pp. 694-702 ◽  
Author(s):  
John Beck Jensen ◽  
Osei Yaw Ampomah ◽  
Richard Darrah ◽  
N. Kent Peters ◽  
T. V. Bhuvaneswari
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Sinorhizobium Meliloti ◽  
Brucella Melitensis ◽  
Sole Source ◽  
Root Surface ◽  
Wild Type ◽  
Major Pathway ◽  
Mesorhizobium Loti ◽  
Infection Threads

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 Rm1021 in infecting alfalfa roots and forming nitrogen-fixing nodules. Possible reasons for their increased competitiveness are discussed.

Role of FlbT in flagellin production in Brucella melitensis

Microbiology ◽  
2011 ◽  
Vol 157 (5) ◽  
pp. 1253-1262 ◽  
Author(s):  
Jonathan Ferooz ◽  
Julien Lemaire ◽  
Jean-Jacques Letesson
Keyword(s):  
Sinorhizobium Meliloti ◽  
Wild Type Strain ◽  
Regulatory Mechanism ◽  
Marked Decrease ◽  
Brucella Melitensis ◽  
Body Structure ◽  
Wild Type ◽  
Reporter Construct ◽  
Flagellar Assembly

It was recently demonstrated that the pathogen Brucella melitensis produces a polar sheathed flagellum under the control of the master regulator FtcR. However, the regulatory mechanism controlling the flagellar assembly remains unknown. In this work, we investigate the flagellar hierarchy of B. melitensis as well as the flagellin FliC regulation. We show that a mutation in fliF or flgE (coding for the basal body structure and the hook, respectively) does not affect FliC synthesis, suggesting that production of FliC does not depend on the flagellar assembly. We demonstrate that FlbT is a FliC activator since inactivation of flbT causes a decrease in fliC expression by using a fliC–lacZ translational reporter construct. Moreover, the quantitative real-time PCR and Western blot analysis show a marked decrease in fliC mRNA and FliC protein level, respectively. Conversely, the B. melitensis wild-type strain overexpressing flaF fails to produce FliC, suggesting an opposite function. Interestingly, the expression of the flbT gene in an ftcR or an flbT mutant restores FliC production, demonstrating that FlbT plays a regulatory checkpoint role in FliC synthesis. This mechanism could be conserved in the Rhizobiales since complementation of an flbT or an ftcR mutant with flbT from Sinorhizobium meliloti restores FliC synthesis.

scholarly journals Nodule Development Induced by Mesorhizobium loti Mutant Strains Affected in Polysaccharide Synthesis

2005 ◽  
Vol 18 (5) ◽  
pp. 446-457 ◽  
Author(s):  
Alejandra L. D'Antuono ◽  
Adriana Casabuono ◽  
Alicia Couto ◽  
Rodolfo A. Ugalde ◽  
Viviana C. Lepek
Keyword(s):  
Pleiotropic Effect ◽  
Nodule Development ◽  
Wild Type ◽  
Mesorhizobium Loti ◽  
O Antigen ◽  
Polysaccharide Synthesis ◽  
Infection Threads ◽  
Surface Polysaccharides ◽  
Hair Curling

The role of Mesorhizobium loti surface polysaccharides on the nodulation process is not yet fully understood. In this article, we describe the nodulation phenotype of mutants affected in the synthesis of lipopolysaccharide (LPS) and β(1,2) cyclic glucan. M. loti lps β2 mutant produces LPS with reduced amount of O-antigen, whereas M. loti lps β1 mutant produces LPS totally devoid of O-antigen. Both genes are clustered in the chromosome. Based on amino acid sequence homology, LPS sugar composition, and enzymatic activity, we concluded that lps β2 codes for an enzyme involved in the transformation of dTDP-glucose into dTDP-rhamnose, the sugar donor of rhamnose for the synthesis of O-antigen. On the other hand, lps β1 codes for a glucosyl transferase involved in the biosynthesis of the O-antigen. Although LPS mutants elicited normal nodules, both show reduced competitiveness compared with the wild type. M. loti β(1-2) cyclic glucan synthase (cgs) mutant induces white, empty, ineffective pseudonodules in Lotus tenuis. Cgs mutant induces normal root hair curling but is unable to induce the formation of infection threads. M. loti cgs mutant was more sensitive to deoxycholate and displayed motility impairment compared with the wild-type strain. This pleiotropic effect depends on calcium concentration and temperature.

scholarly journals Androgen Receptor-Dependent and Independent Atheroprotection by Testosterone in Male Mice

Endocrinology ◽  
2010 ◽  
Vol 151 (11) ◽  
pp. 5428-5437 ◽  
Author(s):  
Johan Bourghardt ◽  
Anna S. K. Wilhelmson ◽  
Camilla Alexanderson ◽  
Karel De Gendt ◽  
Guido Verhoeven ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Apolipoprotein E ◽  
High Fat Diet ◽  
Atherosclerotic Lesion ◽  
Male Mice ◽  
Wild Type ◽  
High Fat ◽  
Lesion Area ◽  
Major Pathway

The atheroprotective effect of testosterone is thought to require aromatization of testosterone to estradiol, but no study has adequately addressed the role of the androgen receptor (AR), the major pathway for the physiological effects of testosterone. We used AR knockout (ARKO) mice on apolipoprotein E-deficient background to study the role of the AR in testosterone atheroprotection in male mice. Because ARKO mice are testosterone deficient, we sham operated or orchiectomized (Orx) the mice before puberty, and Orx mice were supplemented with placebo or a physiological testosterone dose. From 8 to 16 wk of age, the mice consumed a high-fat diet. In the aortic root, ARKO mice showed increased atherosclerotic lesion area (+80%, P < 0.05). Compared with placebo, testosterone reduced lesion area both in Orx wild-type (WT) mice (by 50%, P < 0.001) and ARKO mice (by 24%, P < 0.05). However, lesion area was larger in testosterone-supplemented ARKO compared with testosterone-supplemented WT mice (+57%, P < 0.05). In WT mice, testosterone reduced the presence of a necrotic core in the plaque (80% among placebo-treated vs. 12% among testosterone-treated mice; P < 0.05), whereas there was no significant effect in ARKO mice (P = 0.20). In conclusion, ARKO mice on apolipoprotein E-deficient background display accelerated atherosclerosis. Testosterone treatment reduced atherosclerosis in both WT and ARKO mice. However, the effect on lesion area and complexity was more pronounced in WT than in ARKO mice, and lesion area was larger in ARKO mice even after testosterone supplementation. These results are consistent with an AR-dependent as well as an AR-independent component of testosterone atheroprotection in male mice.

scholarly journals MtBZR1 Plays an Important Role in Nodule Development in Medicago truncatula

2019 ◽  
Vol 20 (12) ◽  
pp. 2941
Author(s):  
Can Cui ◽  
Hongfeng Wang ◽  
Limei Hong ◽  
Yiteng Xu ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Normal Growth ◽  
Dry Mass ◽  
Growth Conditions ◽  
Nodule Development ◽  
Functional Study ◽  
Loss Of Function ◽  
Wild Type

Brassinosteroid (BR) is an essential hormone in plant growth and development. The BR signaling pathway was extensively studied, in which BRASSINAZOLE RESISTANT 1 (BZR1) functions as a key regulator. Here, we carried out a functional study of the homolog of BZR1 in Medicago truncatula R108, whose expression was induced in nodules upon Sinorhizobium meliloti 1021 inoculation. We identified a loss-of-function mutant mtbzr1-1 and generated 35S:MtBZR1 transgenic lines for further analysis at the genetic level. Both the mutant and the overexpression lines of MtBZR1 showed no obvious phenotypic changes under normal growth conditions. After S. meliloti 1021 inoculation, however, the shoot and root dry mass was reduced in mtbzr1-1 compared with the wild type, caused by partially impaired nodule development. The transcriptomic analysis identified 1319 differentially expressed genes in mtbzr1-1 compared with wild type, many of which are involved in nodule development and secondary metabolite biosynthesis. Our results demonstrate the role of MtBZR1 in nodule development in M. truncatula, shedding light on the potential role of BR in legume–rhizobium symbiosis.

Pathways for phosphatidylcholine biosynthesis in bacteria

Microbiology ◽  
2003 ◽  
Vol 149 (12) ◽  
pp. 3461-3471 ◽  
Author(s):  
Fernando Martínez-Morales ◽  
Max Schobert ◽  
Isabel M. López-Lara ◽  
Otto Geiger
Keyword(s):  
Borrelia Burgdorferi ◽  
Legionella Pneumophila ◽  
Bradyrhizobium Japonicum ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Brucella Melitensis ◽  
Membrane Lipid ◽  
Mesorhizobium Loti ◽  
Methylation Pathway ◽  
Phosphatidylcholine Biosynthesis

Phosphatidylcholine (PC) is the major membrane-forming phospholipid in eukaryotes with important structural and signalling functions. Although many prokaryotes lack PC, it can be found in significant amounts in membranes of rather diverse bacteria. Two pathways for PC biosynthesis are known in bacteria, the methylation pathway and the phosphatidylcholine synthase (PCS) pathway. In the methylation pathway, phosphatidylethanolamine is methylated three times to yield PC, in reactions catalysed by one or several phospholipid N-methyltransferases (PMTs). In the PCS pathway, choline is condensed directly with CDP-diacylglyceride to form PC in a reaction catalysed by PCS. Using cell-free extracts, it was demonstrated that Sinorhizobium meliloti, Agrobacterium tumefaciens, Rhizobium leguminosarum, Bradyrhizobium japonicum, Mesorhizobium loti and Legionella pneumophila have both PMT and PCS activities. In addition, Rhodobacter sphaeroides has PMT activity and Brucella melitensis, Pseudomonas aeruginosa and Borrelia burgdorferi have PCS activities. Genes from M. loti and L. pneumophila encoding a Pmt or a Pcs activity and the genes from P. aeruginosa and Borrelia burgdorferi responsible for Pcs activity have been identified. Based on these functional assignments and on genomic data, one might predict that if bacteria contain PC as a membrane lipid, they usually possess both bacterial pathways for PC biosynthesis. However, important pathogens such as Brucella melitensis, P. aeruginosa and Borrelia burgdorferi seem to be exceptional as they possess only the PCS pathway for PC formation.

Alteration of O-specific polysaccharide structure of symbiotically defective Mesorhizobium loti mutant 2213.1 derived from strain NZP2213.

2008 ◽  
Vol 55 (1) ◽  
pp. 191-200 ◽  
Author(s):  
Anna Turska-Szewczuk ◽  
Hubert Pietras ◽  
Wojciech Borucki ◽  
Ryszard Russa
Keyword(s):  
Wild Type Strain ◽  
2D Nmr ◽  
Chain Structure ◽  
Wild Type ◽  
Immunoblot Assay ◽  
Mesorhizobium Loti ◽  
Nmr Data ◽  
Specific Polysaccharide ◽  
C Nmr

Mesorhizobium loti mutant 2213.1 derived from the wild-type strain NZP2213 by Tn5 mutagenesis showed impaired effectiveness of symbiosis with the host plant Lotus corniculatus (Turska-Szewczuk et al., 2007 Microbiol Res, in press). The inability of lipopolysaccharide (LPS) isolated from the mutant 2213.1 strain or de-O-acetylated LPS of the parental cells to inactivate phage A1 particles implicated alterations in the LPS structure. The O-specific polysaccharide of the mutant was studied by chemical analyses along with (1)H and (13)C NMR spectroscopy, which clearly confirmed alterations in the O-chain structure. 2D NMR data showed that the mutant O-polysaccharide consists of a tetrasaccharide repeating unit containing non-substituted as well as O-acetylated or O-methylated 6-deoxytalopyranose residues. Additionally, an immunogold assay revealed a reduced number of gold particles on the mutant bacteroid cell surface, which could result from both a diminished amount of an O-antigenic determinant in mutant LPS and modifications of structural epitopes caused by alterations in O-acetylation or O-methylation of sugar residues. Western immunoblot assay of alkaline de-O-acetylated lipophilic M. loti NZP2213 LPS showed no reactivity with homologous serum indicating a role of O-acetyl groups in its O-specificity.

scholarly journals The Sinorhizobium meliloti RNA Chaperone Hfq Mediates Symbiosis of S. meliloti and Alfalfa

2010 ◽  
Vol 192 (6) ◽  
pp. 1710-1718 ◽  
Author(s):  
Lise Barra-Bily ◽  
Shree P. Pandey ◽  
Annie Trautwetter ◽  
Carlos Blanco ◽  
Graham C. Walker
Keyword(s):  
Sinorhizobium Meliloti ◽  
Growth Parameters ◽  
Loss Of Function ◽  
Plant Host ◽  
Rna Chaperone ◽  
Infection Threads ◽  
Small Regulatory Rnas ◽  
Mutant Phenotypes ◽  
Bacterial Groups

ABSTRACT There exist commonalities between symbiotic Sinorhizobium meliloti and pathogenic Brucella bacteria in terms of extensive gene synteny and the requirements for intracellular survival in their respective hosts. The RNA chaperone Hfq is essential for virulence for several bacterial groups, including Brucella; however, its role in S. meliloti has not been investigated. Our studies of an S. meliloti loss-of-function hfq mutant have revealed that Hfq plays a key role in the establishment of the symbiosis between S. meliloti and its host Medicago sativa. S. meliloti Hfq is involved in controlling the population density under a free-living state and affects the growth parameters and nodulation. An hfq mutant poorly colonizes the infection threads that are necessary for the bacteria to invade the developing nodule. An hfq mutant is severely impaired in its ability to invade plant cells within the nodule, which leads to the formation of small, ineffective nodules unable to fix nitrogen. In culture, the hfq mutant did not accumulate transcripts of nifA, which encodes a key regulator necessary for nitrogen fixation. Hfq may be involved in regulation of several proteins relevant to hfq mutant phenotypes. The crucial role of Hfq in symbiosis suggests that small regulatory RNAs are important for its interactions with its plant host.

scholarly journals Megaplasmid pRme2011a of Sinorhizobium meliloti Is Not Required for Viability

2000 ◽  
Vol 182 (12) ◽  
pp. 3582-3586 ◽  
Author(s):  
Ivan J. Oresnik ◽  
Shu-Lin Liu ◽  
Christopher K. Yost ◽  
Michael F. Hynes
Keyword(s):  
Gel Electrophoresis ◽  
Type Strain ◽  
Sinorhizobium Meliloti ◽  
Wild Type Strain ◽  
Sole Source ◽  
Pulsed Field Gel Electrophoresis ◽  
Selection Strategy ◽  
Wild Type ◽  
Defined Media

ABSTRACT We report the curing of the 1,360-kb megaplasmid pRme2011a fromSinorhizobium meliloti strain Rm2011. With a positive selection strategy that utilized Tn5B12-S containing thesacB gene, we were able to cure this replicon by successive rounds of selecting for deletion formation in vivo. Subsequent Southern blot, Eckhardt gel, and pulsed-field gel electrophoresis analyses were consistent with the hypothesis that the resultant strain was indeed missing pRme2011a. The cured derivative grew as well as the wild-type strain in both complex and defined media but was unable to use a number of substrates as a sole source of carbon on defined media.

scholarly journals Partial Protection against Brucella Infection in Mice by Immunization with Nonpathogenic Alphaproteobacteria

2007 ◽  
Vol 14 (10) ◽  
pp. 1296-1301 ◽  
Author(s):  
M. Victoria Delpino ◽  
Silvia M. Estein ◽  
Carlos A. Fossati ◽  
Pablo C. Baldi
Keyword(s):  
Brucella Abortus ◽  
Sinorhizobium Meliloti ◽  
Brucella Melitensis ◽  
Oral Immunization ◽  
Positive Control ◽  
Oral Route ◽  
Partial Protection ◽  
Mesorhizobium Loti ◽  
The Moment ◽  
Phosphate Buffered Saline

ABSTRACT Previous findings indicate that Brucella antigens and those from nonpathogenic alphaproteobacteria (NPAP) are cross-recognized by the immune system. We hypothesized that immunization with NPAP would protect mice from Brucella infection. Mice were immunized subcutaneously with heat-killed Ochrobactrum anthropi, Sinorhizobium meliloti, Mesorhizobium loti, Agrobacterium tumefaciens, or Brucella melitensis H38 (standard positive control) before intravenous challenge with Brucella abortus 2308. Cross-reacting serum antibodies against Brucella antigens were detected at the moment of challenge in all NPAP-immunized mice. Thirty days after B. abortus challenge, splenic CFU counts were significantly lower in mice immunized with O. anthropi, M. loti, and B. melitensis H38 than in the phosphate-buffered saline controls (protection levels were 0.80, 0.66, and 1.99 log units, respectively). In mice immunized intraperitoneally with cytosoluble extracts from NPAP or Brucella abortus, protection levels were 1.58 for the latter, 0.63 for O. anthropi, and 0.40 for M. loti. To test whether the use of live NPAP would increase protection further, mice were both immunized and challenged by the oral route. Immunization with NPAP induced a significant increase in serum immunoglobulin G (IgG), but not serum or fecal IgA, against Brucella antigens. After challenge, anti-Brucella IgA increased significantly in the sera and feces of mice orally immunized with O. anthropi. For all NPAP, protection levels were higher than those obtained with systemic immunizations but were lower than those obtained by oral immunization with heat-killed B. abortus. These results show that immunization with NPAP, especially O. anthropi, confers partial protection against Brucella challenge. However, such protection is lower than that conferred by immunization with whole Brucella or its cytosoluble fraction.

scholarly journals Exopolysaccharide II Is Relevant for the Survival of Sinorhizobium meliloti under Water Deficiency and Salinity Stress

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4876
Author(s):  
Emiliano Primo ◽  
Pablo Bogino ◽  
Sacha Cossovich ◽  
Emiliano Foresto ◽  
Fiorela Nievas ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Protective Role ◽  
Environmental Stressors ◽  
Saline Stress ◽  
Symbiotic Association ◽  
Atmospheric Nitrogen ◽  
Water Deficiency ◽  
Wild Type ◽  
Induced Stress

Sinorhizobium meliloti is a soil bacterium of great agricultural importance because of its ability to fix atmospheric nitrogen in symbiotic association with alfalfa (Medicago sativa) roots. We looked into the involvement of exopolysaccharides (EPS) in its survival when exposed to different environmental stressors, as well as in bacteria–bacteria and bacteria–substrate interactions. The strains used were wild-type Rm8530 and two strains that are defective in the biosynthesis of EPS II: wild-type Rm1021, which has a non-functional expR locus, and mutant Rm8530 expA. Under stress by water deficiency, Rm8530 remained viable and increased in number, whereas Rm1021 and Rm8530 expA did not. These differences could be due to Rm8530′s ability to produce EPS II. Survival experiments under saline stress showed that viability was reduced for Rm1021 but not for Rm8530 or Rm8530 expA, which suggests the existence of some regulating mechanism dependent on a functional expR that is absent in Rm1021. The results of salinity-induced stress assays regarding biofilm-forming capacity (BFC) and autoaggregation indicated the protective role of EPS II. As a whole, our observations demonstrate that EPS play major roles in rhizobacterial survival.

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