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.

scholarly journals Binding Site Determinants for the LysR-Type Transcriptional Regulator PcaQ in the Legume Endosymbiont Sinorhizobium meliloti

2007 ◽  
Vol 190 (4) ◽  
pp. 1237-1246 ◽  
Author(s):  
Allyson M. MacLean ◽  
Michelle I. Anstey ◽  
Turlough M. Finan
Keyword(s):  
Binding Site ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Transcriptional Start Site ◽  
Mesorhizobium Loti ◽  
Equilibrium Dissociation ◽  
Dyad Symmetry

ABSTRACT LysR-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. In the gram-negative legume endosymbiont Sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the β-ketoadipate pathway are encoded within the pcaDCHGB operon, which is subject to regulation by the LysR-type protein PcaQ. In this work, purified PcaQ was shown to bind strongly (equilibrium dissociation constant, 0.54 nM) to a region at positions −78 to −45 upstream of the pcaD transcriptional start site. Within this region, we defined a PcaQ binding site with dyad symmetry that is required for regulation of pcaD expression in vivo and for binding of PcaQ in vitro. We also demonstrated that PcaQ participates in negative autoregulation by monitoring expression of pcaQ via a transcriptional fusion to lacZ. Although pcaQ homologues are present in many α-proteobacteria, this work describes the first reported purification of this regulator, as well as characterization of its binding site, which is conserved in Agrobacterium tumefaciens, Rhizobium leguminosarum, Rhizobium etli, and Mesorhizobium loti.

scholarly journals pyd Genes of Rhizobium sp. Strain TAL1145 Are Required for Degradation of 3-Hydroxy-4-Pyridone, an Aromatic Intermediate in Mimosine Metabolism

2005 ◽  
Vol 187 (13) ◽  
pp. 4480-4487 ◽  
Author(s):  
Jonathan D. Awaya ◽  
Paul M. Fox ◽  
Dulal Borthakur
Keyword(s):  
Abc Transporter ◽  
Bradyrhizobium Japonicum ◽  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
Structural Genes ◽  
Nodule Bacteria ◽  
Mesorhizobium Loti ◽  
Root Nodule Bacteria ◽  
Low Levels ◽  
Rhizobium Sp

ABSTRACT Rhizobium sp. strain TAL1145 degrades the Leucaena toxin mimosine and its degradation product 3-hydroxy-4-pyridone (HP). The aim of this investigation is to characterize the Rhizobium genes for HP degradation and transport. These genes were localized by subcloning and mutagenesis on a previously isolated cosmid, pUHR263, containing mid genes of TAL1145 required for mimosine degradation. Two structural genes, pydA and pydB, encoding a metacleavage dioxygenase and a hydrolase, respectively, are required for degradation of HP, and three genes, pydC, pydD, and pydE, encoding proteins of an ABC transporter, are involved in the uptake of HP by TAL1145. These genes are induced by HP, although both pydA and pydB show low levels of expression without HP. pydA and pydB are cotranscribed, while pydC, pydD, and pydE are each transcribed from separate promoters. PydA and PydB show no homology with other dioxygenases and hydrolases in Sinorhizobium meliloti, Mesorhizobium loti, and Bradyrhizobium japonicum. Among various root nodule bacteria, the ability to degrade mimosine or HP is unique to some Leucaena-nodulating Rhizobium strains.

scholarly journals Nickel Availability and hupSL Activation by Heterologous Regulators Limit Symbiotic Expression of theRhizobium leguminosarum bv. Viciae Hydrogenase System in Hup− Rhizobia

2000 ◽  
Vol 66 (3) ◽  
pp. 937-942 ◽  
Author(s):  
Belén Brito ◽  
Jorge Monza ◽  
Juan Imperial ◽  
Tomás Ruiz-Argüeso ◽  
Jose Manuel Palacios
Keyword(s):  
Transcriptional Activation ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Transcriptional Regulator ◽  
Hydrogen Uptake ◽  
Hydrogenase Activity ◽  
Structural Genes ◽  
Mesorhizobium Loti ◽  
Genes Expression ◽  
Relevant Factors

ABSTRACT A limited number of Rhizobium andBradyrhizobium strains possess a hydrogen uptake (Hup) system that recycles the hydrogen released from the nitrogen fixation process in legume nodules. To extend this ability to rhizobia that nodulate agronomically important crops, we investigated factors that affect the expression of a cosmid-borne Hup system from Rhizobium leguminosarum bv. viciae UPM791 in R. leguminosarumbv. viciae, Rhizobium etli, Mesorhizobium loti, and Sinorhizobium meliloti Hup− strains. After cosmid pAL618 carrying the entire hup system of strain UPM791 was introduced, all recipient strains acquired the ability to oxidize H2 in symbioses with their hosts, although the levels of hydrogenase activity were found to be strain and species dependent. The levels of hydrogenase activity were correlated with the levels of nickel-dependent processing of the hydrogenase structural polypeptides and with transcription of structural genes. Expression of the NifA-dependent hupSL promoter varied depending on the genetic background, while the hyp operon, which is controlled by the FnrN transcriptional regulator, was expressed at similar levels in all recipient strains. With the exception of theR. etli-bean symbiosis, the availability of nickel to bacteroids strongly affected hydrogenase processing and activity in the systems tested. Our results indicate that efficient transcriptional activation by heterologous regulators and processing of the hydrogenase as a function of the availability of nickel to the bacteroid are relevant factors that affect hydrogenase expression in heterologous rhizobia.

Phospholipid synthesis in Borrelia burgdorferi: BB0249 and BB0721 encode functional phosphatidylcholine synthase and phosphatidylglycerolphosphate synthase proteins

Microbiology ◽  
2004 ◽  
Vol 150 (2) ◽  
pp. 391-397 ◽  
Author(s):  
Xing-Guo Wang ◽  
Joanna P. Scagliotti ◽  
Linden T. Hu
Keyword(s):  
Borrelia Burgdorferi ◽  
Sinorhizobium Meliloti ◽  
Biosynthetic Pathways ◽  
Phospholipid Synthesis ◽  
Membrane Phospholipids ◽  
Bacterial Membranes ◽  
E Coli ◽  
Methylation Pathway ◽  
And Function

Phospholipids are an important component of bacterial membranes. Borrelia burgdorferi differs from many other bacteria in that it contains only two major membrane phospholipids: phosphatidylglycerol (PG) and phosphatidylcholine (PC). B. burgdorferi appears to lack enzymes required for synthesis of PC through the well-described methylation pathway. However, B. burgdorferi does contain a gene (BB0249) with significant identity to a recently described phosphatidylcholine synthase gene (pcs) of Sinorhizobium meliloti. B. burgdorferi also contains a gene (BB0721) with significant identity to the gene (pgs) encoding phosphatidylglycerolphosphate synthase, an enzyme in the synthetic pathway of PG. Activity of BB0249 was confirmed by cloning the gene into Escherichia coli, which does not produce PC. Transformation with a plasmid carrying BB0249 resulted in production of PC by E. coli, but only in the presence of exogenously supplied choline, as would be predicted for a Pcs. Because loss of Pgs activity is lethal to E. coli, activity of BB0721 was confirmed by the ability of BB0721 to complement an E. coli Pgs− mutant. A plasmid containing BB0721 was transformed into a Pgs− mutant of E. coli containing a copy of the native gene on a temperature-regulated plasmid. The temperature-regulated plasmid was exchanged for a plasmid containing BB0721 and it was shown that BB0721 was able to replace the lost Pgs function and restore bacterial growth. This study has established the existence and function of two critical enzymes in the synthesis of PC and PG in B. burgdorferi. Understanding of the biosynthetic pathways of PC and PG in B. burgdorferi is the first step in delineating the role of these phospholipids in the pathogenesis of Lyme disease.

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 Generation of New Hydrogen-RecyclingRhizobiaceae Strains by Introduction of a Novelhup Minitransposon

2000 ◽  
Vol 66 (10) ◽  
pp. 4292-4299 ◽  
Author(s):  
Elena Báscones ◽  
Juan Imperial ◽  
Tomás Ruiz-Argüeso ◽  
Jose Manuel Palacios
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
General Procedure ◽  
Large Subunit ◽  
Antibiotic Resistance Gene ◽  
Insertion Site ◽  
Immunoblot Analysis ◽  
Hydrogenase Activity ◽  
Mesorhizobium Loti ◽  
Legume Symbiosis

ABSTRACT Hydrogen evolution by nitrogenase is a source of inefficiency for the nitrogen fixation process by the Rhizobium-legume symbiosis. To develop a strategy to generate rhizobial strains with H2-recycling ability, we have constructed a Tn5derivative minitransposon (TnHB100) that contains the ca. 18-kb H2 uptake (hup) gene cluster fromRhizobium leguminosarum bv. viciae UPM791. Bacteroids from TnHB100-containing strains of R. leguminosarum bv. viciae PRE, Bradyrhizobium japonicum, R. etli, and Mesorhizobium loti expressed high levels of hydrogenase activity that resulted in full recycling of the hydrogen evolved by nitrogenase in nodules. Efficient processing of the hydrogenase large subunit (HupL) in these strains was shown by immunoblot analysis of bacteroid extracts. In contrast, Sinorhizobium meliloti,M. ciceri, and R. leguminosarum bv. viciae UML2 strains showed poor expression of the hup system that resulted in H2-evolving nodules. For the latter group of strains, no immunoreactive material was detected in bacteroid extracts using anti-HupL antiserum, suggesting a low level of transcription ofhup genes or HupL instability. A general procedure for the characterization of the minitransposon insertion site and removal of antibiotic resistance gene included in TnHB100 has been developed and used to generate engineered strains suitable for field release.

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.

TheglcBlocus ofRhizobium leguminosarumVF39 encodes an arabinose-inducible malate synthase

2002 ◽  
Vol 48 (10) ◽  
pp. 922-932 ◽  
Author(s):  
Alejandro García-de los Santos ◽  
Alejandro Morales ◽  
Laura Baldomá ◽  
Scott R.D Clark ◽  
Susana Brom ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Plant Cell Wall ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
Mesorhizobium Loti ◽  
Malate Synthase G ◽  
Similar Genome Organization ◽  
The Glyoxylate Cycle

In the course of a study conducted to isolate genes upregulated by plant cell wall sugars, we identified an arabinose-inducible locus from a transcriptional fusion library of Rhizobium leguminosarum VF39, carrying random insertions of the lacZ transposon Tn5B22. Sequence analysis of the locus disrupted by the transposon revealed a high similarity to uncharacterized malate synthase G genes from Sinorhizobium meliloti, Agrobacterium tumefaciens, and Mesorhizobium loti. This enzyme catalyzes the condensation of glyoxylate and acetyl-CoA to yield malate and CoA and is thought to be a component of the glyoxylate cycle, which allows microorganisms to grow on two carbon compounds. Enzyme assays showed that a functional malate synthase is encoded in the glcB gene of R. leguminosarum and that its expression is induced by arabinose, glycolate, and glyoxylate. An Escherichia coli aceB glcB mutant, complemented with the R. leguminosarum PCR-amplified gene, recovered malate synthase activity. A very similar genome organization of the loci containing malate synthase and flanking genes was observed in R. leguminosarum, S. meliloti, and A. tumefaciens. Pea plants inoculated with the glcB mutant or the wild-type strain showed no significant differences in nitrogen fixation. This is the first report regarding the characterization of a mutant in one of the glyoxylate cycle enzymes in the rhizobia.Key words: Rhizobium, malate synthase, glyoxylate cycle, arabinose metabolism.

scholarly journals Thiamine Is Synthesized by a Salvage Pathway in Rhizobium leguminosarum bv. viciae Strain 3841

2006 ◽  
Vol 188 (18) ◽  
pp. 6661-6668 ◽  
Author(s):  
R. Karunakaran ◽  
K. Ebert ◽  
S. Harvey ◽  
M. E. Leonard ◽  
V. Ramachandran ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
De Novo ◽  
Fluorescent Microscopy ◽  
Good Growth ◽  
Wild Type ◽  
Salvage Pathway ◽  
Mesorhizobium Loti ◽  
Reverse Transcription Pcr

ABSTRACT In the absence of added thiamine, Rhizobium leguminosarum bv. viciae strain 3841 does not grow in liquid medium and forms only “pin” colonies on agar plates, which contrasts with the good growth of Sinorhizobium meliloti 1021, Mesorhizobium loti 303099, and Rhizobium etli CFN42. These last three organisms have thiCOGE genes, which are essential for de novo thiamine synthesis. While R. leguminosarum bv. viciae 3841 lacks thiCOGE, it does have thiMED. Mutation of thiM prevented formation of pin colonies on agar plates lacking added thiamine, suggesting thiamine intermediates are normally present. The putative functions of ThiM, ThiE, and ThiD are 4-methyl-5-(β-hydroxyethyl) thiazole (THZ) kinase, thiamine phosphate pyrophosphorylase, and 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) kinase, respectively. This suggests that a salvage pathway operates in R. leguminosarum, and addition of HMP and THZ enabled growth at the same rate as that enabled by thiamine in strain 3841 but elicited no growth in the thiM mutant (RU2459). There is a putative thi box sequence immediately upstream of the thiM, and a gfp-mut3.1 fusion to it revealed the presence of a promoter that is strongly repressed by thiamine. Using fluorescent microscopy and quantitative reverse transcription-PCR, it was shown that thiM is expressed in the rhizosphere of vetch and pea plants, indicating limitation for thiamine. Pea plants infected by RU2459 were not impaired in nodulation or nitrogen fixation. However, colonization of the pea rhizosphere by the thiM mutant was impaired relative to that of the wild type. Overall, the results show that a thiamine salvage pathway operates to enable growth of Rhizobium leguminosarum in the rhizosphere, allowing its survival when thiamine is limiting.

scholarly journals Occurrence of Choline and Glycine Betaine Uptake and Metabolism in the Family Rhizobiaceae and Their Roles in Osmoprotection

1999 ◽  
Vol 65 (5) ◽  
pp. 2072-2077 ◽  
Author(s):  
Eric Boncompagni ◽  
Magne Østerås ◽  
Marie-Christine Poggi ◽  
Daniel le Rudulier
Keyword(s):  
Glycine Betaine ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Physiological Role ◽  
Betaine Aldehyde Dehydrogenase ◽  
Choline Uptake ◽  
Rhizobium Tropici ◽  
Mesorhizobium Loti ◽  
The Family

ABSTRACT The role of glycine betaine and choline in osmoprotection of various Rhizobium, Sinorhizobium,Mesorhizobium, Agrobacterium, andBradyrhizobium reference strains which display a large variation in salt tolerance was investigated. When externally provided, both compounds enhanced the growth of Rhizobium tropici,Sinorhizobium meliloti, Sinorhizobium fredii,Rhizobium galegae, Agrobacterium tumefaciens,Mesorhizobium loti, and Mesorhizobium huakuii, demonstrating their utilization as osmoprotectants. However, both compounds were inefficient for the most salt-sensitive strains, such asRhizobium leguminosarum (all biovars), Agrobacterium rhizogenes, Rhizobium etli, and Bradyrhizobium japonicum. Except for B. japonicum, all strains exhibit transport activity for glycine betaine and choline. When the medium osmolarity was raised, choline uptake activity was inhibited, whereas glycine betaine uptake was either increased in R. leguminosarum and S. meliloti or, more surprisingly, reduced in R. tropici, S. fredii, and M. loti. The transport of glycine betaine was increased by growing the cells in the presence of the substrate. With the exception ofB. japonicum, all strains were able to use glycine betaine and choline as sole carbon and nitrogen sources. This catabolic function, reported for only a few soil bacteria, could increase competitiveness of rhizobial species in the rhizosphere. Choline dehydrogenase and betaine-aldehyde dehydrogenase activities were present in the cells of all strains with the exception of M. huakuii and B. japonicum. The main physiological role of glycine betaine in the family Rhizobiaceae seems to be as an energy source, while its contribution to osmoprotection is restricted to certain strains.

Sign in / Sign up

Export Citation Format

Share Document