Comparison of the symbiotic and competition phenotypes of Sinorhizobium meliloti PHB synthesis and degradation pathway mutants

2005 ◽  
Vol 51 (7) ◽  
pp. 599-604 ◽  
Author(s):  
P Aneja ◽  
A Zachertowska ◽  
T C Charles
Keyword(s):  
Sinorhizobium Meliloti ◽  
Degradation Pathway ◽  
Nodule Occupancy ◽  
Wild Type ◽  
Term Survival ◽  
Mutant Strains ◽  
Key Factor ◽  
Carbon Excess ◽  
Synthesis And Degradation

The competitive abilities of Sinorhizobium meliloti mutant strains containing lesions in the PHB synthesis (phbC) and degradation (bdhA) pathways were compared. While the bdhA mutant showed no noticeable symbiotic defects on alfalfa host plants when inoculated alone, in mixed inoculation experiments it was found to be less competitive than the wild type for nodule occupancy. Long-term survival of the bdhA mutant on a carbon-limiting medium was not affected. However, when subjected to competition with the wild-type strain in periodic subculturing through alternating carbon-limiting and carbon-excess conditions, the bdhA mutant performed poorly. A more severe defect in competition for growth and nodule occupancy was observed with a mutant unable to synthesize PHB (phbC). These results indicate that the ability to efficiently deposit cellular PHB stores is a key factor influencing competitive survival under conditions of fluctuating nutrient carbon availability, whereas the ability to use these stores is less important.Key words: Sinorhizobium meliloti, PHB metabolism, competition.

scholarly journals Contextualizing Autophagy during Gametogenesis and Preimplantation Embryonic Development

2021 ◽  
Vol 22 (12) ◽  
pp. 6313
Author(s):  
Marcelo T. Moura ◽  
Laís B. Latorraca ◽  
Fabíola F. Paula-Lopes
Keyword(s):  
Embryonic Development ◽  
Germ Cells ◽  
Physiological Role ◽  
Degradation Pathway ◽  
Environmental Stressors ◽  
Preimplantation Embryos ◽  
Environmental Cues ◽  
Term Survival ◽  
Assisted Reproduction Technologies

Mammals face environmental stressors throughout their lifespan, which may jeopardize cellular homeostasis. Hence, these organisms have acquired mechanisms to cope with stressors by sensing, repairing the damage, and reallocating resources to increase the odds of long-term survival. Autophagy is a pro-survival lysosome-mediated cytoplasm degradation pathway for organelle and macromolecule recycling. Furthermore, autophagy efflux increases, and this pathway becomes idiosyncratic depending upon developmental and environmental contexts. Mammalian germ cells and preimplantation embryos are attractive models for dissecting autophagy due to their metastable phenotypes during differentiation and exposure to varying environmental cues. The aim of this review is to explore autophagy during mammalian gametogenesis, fertilization and preimplantation embryonic development by contemplating its physiological role during development, under key stressors, and within the scope of assisted reproduction technologies.

scholarly journals Inositol Catabolism, a Key Pathway in Sinorhizobium meliloti for Competitive Host Nodulation

2010 ◽  
Vol 76 (24) ◽  
pp. 7972-7980 ◽  
Author(s):  
Petra R. A. Kohler ◽  
Jasmine Y. Zheng ◽  
Elke Schoffers ◽  
Silvia Rossbach
Keyword(s):  
Bacillus Subtilis ◽  
Carbon Source ◽  
Sole Carbon Source ◽  
Sinorhizobium Meliloti ◽  
Mutational Analysis ◽  
Nodule Occupancy ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Catabolic Pathway ◽  
Inositol Dehydrogenase

ABSTRACT The nitrogen-fixing symbiont of alfalfa, Sinorhizobium meliloti, is able to use myo-inositol as the sole carbon source. Putative inositol catabolism genes (iolA and iolRCDEB) have been identified in the S. meliloti genome based on their similarities with the Bacillus subtilis iol genes. In this study, functional mutational analysis revealed that the iolA and iolCDEB genes are required for growth not only with the myo-isomer but also for growth with scyllo- and d-chiro-inositol as the sole carbon source. An additional, hypothetical dehydrogenase of the IdhA/MocA/GFO family encoded by the smc01163 gene was found to be essential for growth with scyllo-inositol, whereas the idhA-encoded myo-inositol dehydrogenase was responsible for the oxidation of d-chiro-inositol. The putative regulatory iolR gene, located upstream of iolCDEB, encodes a repressor of the iol genes, negatively regulating the activity of the myo- and the scyllo-inositol dehydrogenases. Mutants with insertions in the iolA, smc01163, and individual iolRCDE genes could not compete against the wild type in a nodule occupancy assay on alfalfa plants. Thus, a functional inositol catabolic pathway and its proper regulation are important nutritional or signaling factors in the S. meliloti-alfalfa symbiosis.

scholarly journals Malic Enzyme Cofactor and Domain Requirements for Symbiotic N2 Fixation by Sinorhizobium meliloti

2006 ◽  
Vol 189 (1) ◽  
pp. 160-168 ◽  
Author(s):  
Michael J. Mitsch ◽  
Alison Cowie ◽  
Turlough M. Finan
Keyword(s):  
Amino Acid ◽  
Malic Enzyme ◽  
Sinorhizobium Meliloti ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
High Ratio ◽  
Terminal Region ◽  
Wild Type ◽  
Mutant Strains ◽  
Alfalfa Root

ABSTRACT The NAD+-dependent malic enzyme (DME) and the NADP+-dependent malic enzyme (TME) of Sinorhizobium meliloti are representatives of a distinct class of malic enzymes that contain a 440-amino-acid N-terminal region homologous to other malic enzymes and a 330-amino-acid C-terminal region with similarity to phosphotransacetylase enzymes (PTA). We have shown previously that dme mutants of S. meliloti fail to fix N2 (Fix−) in alfalfa root nodules, whereas tme mutants are unimpaired in their N2-fixing ability (Fix+). Here we report that the amount of DME protein in bacteroids is 10 times greater than that of TME. We therefore investigated whether increased TME activity in nodules would allow TME to function in place of DME. The tme gene was placed under the control of the dme promoter, and despite elevated levels of TME within bacteroids, no symbiotic nitrogen fixation occurred in dme mutant strains. Conversely, expression of dme from the tme promoter resulted in a large reduction in DME activity and symbiotic N2 fixation. Hence, TME cannot replace the symbiotic requirement for DME. In further experiments we investigated the DME PTA-like domain and showed that it is not required for N2 fixation. Thus, expression of a DME C-terminal deletion derivative or the Escherichia coli NAD+-dependent malic enzyme (sfcA), both of which lack the PTA-like region, restored wild-type N2 fixation to a dme mutant. Our results have defined the symbiotic requirements for malic enzyme and raise the possibility that a constant high ratio of NADPH + H+ to NADP in nitrogen-fixing bacteroids prevents TME from functioning in N2-fixing bacteroids.

scholarly journals A Role for Single-Stranded Exonucleases in the Use of DNA as a Nutrient

2009 ◽  
Vol 191 (11) ◽  
pp. 3712-3716 ◽  
Author(s):  
Vyacheslav Palchevskiy ◽  
Steven E. Finkel
Keyword(s):  
Escherichia Coli ◽  
Bacterial Cells ◽  
Wild Type ◽  
Nutrient Source ◽  
Term Survival ◽  
Natural Competence ◽  
E Coli ◽  
Double Stranded Dna ◽  
Better Than

ABSTRACT Nutritional competence is the ability of bacterial cells to utilize exogenous double-stranded DNA molecules as a nutrient source. We previously identified several genes in Escherichia coli that are important for this process and proposed a model, based on models of natural competence and transformation in bacteria, where it is assumed that single-stranded DNA (ssDNA) is degraded following entry into the cytoplasm. Since E. coli has several exonucleases, we determined whether they play a role in the long-term survival and the catabolism of DNA as a nutrient. We show here that mutants lacking either ExoI, ExoVII, ExoX, or RecJ are viable during all phases of the bacterial life cycle yet cannot compete with wild-type cells during long-term stationary-phase incubation. We also show that nuclease mutants, alone or in combination, are defective in DNA catabolism, with the exception of the ExoX− single mutant. The ExoX− mutant consumes double-stranded DNA better than wild-type cells, possibly implying the presence of two pathways in E. coli for the processing of ssDNA as it enters the cytoplasm.

scholarly journals Long-Term Survival of Campylobacter jejuni at Low Temperatures Is Dependent on Polynucleotide Phosphorylase Activity

2009 ◽  
Vol 75 (23) ◽  
pp. 7310-7318 ◽  
Author(s):  
Nabila Haddad ◽  
Christopher M. Burns ◽  
Jean Michel Bolla ◽  
Hervé Prévost ◽  
Michel Fédérighi ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Low Temperatures ◽  
Survival Rates ◽  
Polynucleotide Phosphorylase ◽  
Wild Type ◽  
Term Survival ◽  
Poultry Products ◽  
Bacterial Gastroenteritis

ABSTRACT Campylobacter jejuni is a leading cause of bacterial gastroenteritis worldwide. Infection generally occurs after ingestion of contaminated poultry products, usually conserved at low temperatures. The mechanisms promoting survival of C. jejuni in the cold remain poorly understood despite several investigations. The present study provides insight into the survival mechanism by establishing the involvement of polynucleotide phosphorylase (PNPase), a 3′-5′ exoribonuclease with multiple biological functions in cold survival. The role of PNPase was demonstrated genetically using strains with altered pnp genes (which encode PNPase) created in C. jejuni F38011 and C. jejuni 81-76 backgrounds. Survival assays carried out at low temperatures (4 and 10°C) revealed a difference of 3 log CFU/ml between the wild-type and the pnp deletion (Δpnp) strains. This did not result from a general requirement for PNPase because survival rates of the strains were similar at higher growth temperatures (37 or 42°C). trans-Complementation with plasmid pNH04 carrying the pnp gene under the control of its natural promoter restored the cold survival phenotype to the pnp deletion strains (at 4 and 10°C) but not to the same level as the wild type. In this study we demonstrate the role of PNPase in low-temperature survival of C. jejuni and therefore attribute a novel biological function to PNPase directly related to human health.

scholarly journals Deficiency of a Sinorhizobium meliloti bacA Mutant in Alfalfa Symbiosis Correlates with Alteration of the Cell Envelope

2002 ◽  
Vol 184 (20) ◽  
pp. 5625-5632 ◽  
Author(s):  
Gail P. Ferguson ◽  
R. Martin Roop ◽  
Graham C. Walker
Keyword(s):  
Bacterial Cell ◽  
Sinorhizobium Meliloti ◽  
Cell Envelope ◽  
Carbohydrate Composition ◽  
Animal Cells ◽  
Long Chain Fatty Acid ◽  
Term Survival ◽  
Increased Sensitivity ◽  
Acidic Compartments

ABSTRACT The BacA protein is essential for the long-term survival of Sinorhizobium meliloti and Brucella abortus within acidic compartments in plant and animal cells, respectively. Since both the S. meliloti and B. abortus bacA mutants have an increased resistance to bleomycin, it was hypothesized that BacA was a transporter of bleomycin and bleomycin-like compounds into the bacterial cell. However, our finding that the S. meliloti bacA mutant also has an increased sensitivity to detergents, a hydrophobic dye, ethanol, and acid pH supported a model in which BacA function affects the bacterial cell envelope. In addition, an S. meliloti lpsB mutant that is defective at a stage in infection of the host similar to that found for a bacA mutant is also sensitive to the same agents, and the carbohydrate content of its lipopolysaccharide (LPS) is altered. However, analysis of crude preparations of the bacA mutant LPS suggested that, unlike that for LpsB, BacA function did not affect the carbohydrate composition of the LPS. Rather, we found that at least one function of BacA is to affect the distribution of LPS fatty acids, including a very-long-chain fatty acid thought to be unique to the α-proteobacteria, including B. abortus.

scholarly journals The Succinyl and Acetyl Modifications of Succinoglycan Influence Susceptibility of Succinoglycan to Cleavage by the Rhizobium meliloti Glycanases ExoK and ExsH

1998 ◽  
Vol 180 (16) ◽  
pp. 4184-4191 ◽  
Author(s):  
Gregory M. York ◽  
Graham C. Walker
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Meliloti ◽  
Low Molecular Weight ◽  
Wild Type ◽  
Mutant Strains ◽  
Acetyl Group

ABSTRACT In Rhizobium meliloti (Sinorhizobium meliloti) cultures, the endo-1,3-1,4-β-glycanases ExoK and ExsH depolymerize nascent high-molecular-weight (HMW) succinoglycan to yield low-molecular-weight (LMW) succinoglycan. We report here that the succinyl and acetyl modifications of succinoglycan influence the susceptibility of succinoglycan to cleavage by these glycanases. It was previously shown that exoH mutants, which are blocked in the succinylation of succinoglycan, exhibit a defect in the production of LMW succinoglycan. We have determined that exoZ mutants, which are blocked in the acetylation of succinoglycan, exhibit an increase in production of LMW succinoglycan. For both wild-type andexoZ mutant strains, production of LMW succinoglycan is dependent on the exoK + andexsH + genes, implying that the ExoK and ExsH glycanases cleave HMW succinoglycan to yield LMW succinoglycan. By supplementing cultures of glycanase-deficient strains with exogenously added ExoK or ExsH, we have demonstrated directly that the absence of the acetyl group increases the susceptibility of succinoglycan to cleavage by ExoK and ExsH, that the absence of the succinyl group decreases the susceptibility of succinoglycan to cleavage, and that the succinyl effect outweighs the acetyl effect for succinoglycan lacking both modifications. Strikingly, nonsuccinylated succinoglycan actually can be cleaved by ExoK and ExsH to yield LMW succinoglycan, but only when the glycanases are added to cultures at greater than physiologically relevant concentrations. Thus, we conclude that the molecular weight distribution of succinoglycan in R. meliloti cultures is determined by both the levels of ExoK and ExsH glycanase expression and the susceptibility of succinoglycan to cleavage.

Long-term survival in primary glioblastoma revisited: The contribution of isocitrate dehydrogenase mutations.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 2027-2027
Author(s):  
Michael Weller ◽  
Bettina Hentschel ◽  
Matthias Simon ◽  
Manfred Westphal ◽  
Gabriele Schackert ◽  
...  
Keyword(s):  
Promoter Methylation ◽  
Mgmt Promoter Methylation ◽  
Molecular Characteristics ◽  
Wild Type ◽  
Who Grade ◽  
Term Survival ◽  
Long Term Survival ◽  
Tp53 Mutations ◽  
Mgmt Promoter

2027 Background: The determinants of long-term survival in glioblastoma have remained largely obscure. Isocitrate dehydrogenase (IDH) 1 or 2 mutations are common in WHO grade 2/3 gliomas, but rare in primary glioblastomas, and associated with longer survival. Methods: We compared clinical and molecular characteristics of 69 patients with centrally confirmed glioblastoma and survival > 36 months (LTS-36), including 33 patients surviving > 60 months (LTS-60), with 259 patients surviving < 36 months. MGMT promoter methylation, 1p/19q codeletions, EGFR amplification, TP53 mutations and IDH1/2mutations were determined by standard techniques. Results: The rate of IDH1/2 mutations in LTS-36 patients was 34% (23/67 patients) as opposed to 4.3% in controls (11/257 patients). Long-term survivors with IDH1/2 -mutant glioblastomas were younger, had almost no EGFR amplifications, but exhibited more often 1p/19q codeletions and TP53 mutations than LTS patients with IDH1/2 wild-type glioblastomas. Among LTS-36 patients, wild-type TP53 status, MGMT promoter methylation, and absence of EGFR amplification, but not IDH1/2 mutation, were associated with prolonged survival. Among 11 patients with IDH1/2-mutant glioblastomas without long-term survival, the only difference to IDH1/2-mutant long-term survivors was less frequent MGMT promoter methylation. Compared with LTS-36 patients, LTS-60 patients had been treated initially with radiotherapy alone and had TP53 mutations less frequently. Conclusions: IDH1/2 mutations define a subgroup of tumors of LTS patients that exhibit molecular characteristics of WHO grade 2/3 gliomas and secondary glioblastomas. Determinants of LTS with IDH1/2 wild-type glioblastomas, which exhibit typical molecular features of primary glioblastomas, beyond MGMT promoter methylation, remain to be identified.

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