scholarly journals Nodulation Gene Regulation and Quorum Sensing Control Density-Dependent Suppression and Restriction of Nodulation in the Bradyrhizobium japonicum-Soybean Symbiosis

2008 ◽  
Vol 74 (12) ◽  
pp. 3749-3756 ◽  
Author(s):  
Siriluck Jitacksorn ◽  
Michael J. Sadowsky
Keyword(s):  
Population Density ◽  
Cell Density ◽  
Bradyrhizobium Japonicum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Inoculum Density ◽  
Complex Medium ◽  
Wild Type ◽  
Soybean Genotype ◽  
Density Dependent

ABSTRACT The nodulation of Glycine max cv. Lambert and the nodulation-restricting plant introduction (PI) genotype PI 417566 by wild-type Bradyrhizobium japonicum USDA110 is regulated in a population-density-dependent manner. Nodulation on both plant genotypes was suppressed (inhibited) when plants received a high-density inoculum (109 cells/ml) of strain USDA110 grown in complex medium, and more nodules were produced on plants receiving a low-cell-density inoculum (105 cells/ml). Since cell-free supernatants from strain USDA110 grown to high cell density in complex medium decreased the expression of an nodY-lacZ fusion, this phenomenon was attributed to bradyoxetin-induced repression of nod gene expression. Inoculation of either the permissive soybean genotype (cv. Lambert) or PI 417566 with 109 cells/ml of the nodD2, nolA, nodW, and nwsB mutants of USDA110 enhanced nodulation (up to 24%) relative to that seen with inoculations done with 105 cells/ml of the mutants or the wild-type strain, indicating that these genes are involved in population-density-dependent nodulation of soybeans. In contrast, the number of nodules produced by an nodD1 mutant on either soybean genotype was less than those seen with the wild-type strain inoculated at a low inoculum density. The nodD2 mutant outcompeted B. japonicum strain USDA123 for nodulation of G. max cv. Lambert at a high or low inoculum density, and the results of root-tip-marking and time-to-nodulate studies indicated that the nolA and nodD2 mutants nodulated this soybean genotype faster than wild-type USDA110. Taken together, the results from these studies indicate that the nodD2 mutant of B. japonicum may be useful to enhance soybean nodulation at high inoculum densities and that NodD2 is a key repressor influencing host-controlled restriction of nodulation, density-dependent suppression of nodulation, perception of bradyoxetin, and competitiveness in the soybean-B. japonicum symbiosis.

scholarly journals Functional Role of Bradyrhizobium japonicum Trehalose Biosynthesis and Metabolism Genes during Physiological Stress and Nodulation

2009 ◽  
Vol 76 (4) ◽  
pp. 1071-1081 ◽  
Author(s):  
Masayuki Sugawara ◽  
Eddie J. Cytryn ◽  
Michael J. Sadowsky
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Type Strain ◽  
Double Mutant ◽  
Wild Type Strain ◽  
Physiological Stress ◽  
Desiccation Stress ◽  
Wild Type ◽  
Trehalose Biosynthesis ◽  
Soybean Plants ◽  
Trehalose Accumulation

ABSTRACT Trehalose, a disaccharide accumulated by many microorganisms, acts as a protectant during periods of physiological stress, such as salinity and desiccation. Previous studies reported that the trehalose biosynthetic genes (otsA, treS, and treY) in Bradyrhizobium japonicum were induced by salinity and desiccation stresses. Functional mutational analyses indicated that disruption of otsA decreased trehalose accumulation in cells and that an otsA treY double mutant accumulated an extremely low level of trehalose. In contrast, trehalose accumulated to a greater extent in a treS mutant, and maltose levels decreased relative to that seen with the wild-type strain. Mutant strains lacking the OtsA pathway, including the single, double, and triple ΔotsA, ΔotsA ΔtreS and ΔotsA ΔtreY, and ΔotsA ΔtreS ΔtreY mutants, were inhibited for growth on 60 mM NaCl. While mutants lacking functional OtsAB and TreYZ pathways failed to grow on complex medium containing 60 mM NaCl, there was no difference in the viability of the double mutant strain when cells were grown under conditions of desiccation stress. In contrast, mutants lacking a functional TreS pathway were less tolerant of desiccation stress than the wild-type strain. Soybean plants inoculated with mutants lacking the OtsAB and TreYZ pathways produced fewer mature nodules and a greater number of immature nodules relative to those produced by the wild-type strain. Taken together, results of these studies indicate that stress-induced trehalose biosynthesis in B. japonicum is due mainly to the OtsAB pathway and that the TreS pathway is likely involved in the degradation of trehalose to maltose. Trehalose accumulation in B. japonicum enhances survival under conditions of salinity stress and plays a role in the development of symbiotic nitrogen-fixing root nodules on soybean plants.

scholarly journals A Two-Component Regulator Mediates Population-Density-Dependent Expression of the Bradyrhizobium japonicum Nodulation Genes

2002 ◽  
Vol 184 (6) ◽  
pp. 1759-1766 ◽  
Author(s):  
John Loh ◽  
Dasharath P. Lohar ◽  
Brett Andersen ◽  
Gary Stacey
Keyword(s):  
Gene Expression ◽  
Population Density ◽  
Conditioned Medium ◽  
Bradyrhizobium Japonicum ◽  
Response Regulator ◽  
High Population ◽  
Wild Type ◽  
Population Densities ◽  
Density Dependent ◽  
Culture Density

ABSTRACT Bradyrhizobium japonicum nod gene expression was previously shown to be population density dependent. Induction of the nod genes is highest at low culture density and repressed at high population densities. This repression involves both NolA and NodD2 and is mediated by an extracellular factor found in B. japonicum conditioned medium. NolA and NodD2 expression is maximal at high population densities. We demonstrate here that a response regulator, encoded by nwsB, is required for the full expression of the B. japonicum nodYABC operon. In addition, NwsB is also required for the population-density-dependent expression of both nolA and nodD2. Expression of nolA and nodD2 in the nwsB mutant remained at a basal level, even at high culture densities. The nwsB defect could be complemented by overexpression of a second response regulator, NodW. Consistent with the fact that NolA and NodD2 repress nod gene expression, the expression of a nodY-lacZ fusion in the nwsB mutant was unaffected by culture density. In plant assays with GUS fusions, nodules infected with the wild type showed no nodY-GUS expression. In contrast, nodY-GUS expression was not repressed in nodules infected with the nwsB mutant. Nodule competition assays between the wild type and the nwsB mutant revealed that the addition of conditioned medium resulted in a competitive advantage for the nwsB mutant.

Bradyrhizobium japonicum Mutants Defective in Cyclic β-Glucan Synthesis Show Enhanced Sensitivity to Plant Defense Responses

2001 ◽  
Vol 56 (7-8) ◽  
pp. 581-584 ◽  
Author(s):  
Axel Mithöfer ◽  
Arvind A. Bhagwat ◽  
Donald L. Keister ◽  
Jürgen Ebel
Keyword(s):  
Plant Defense ◽  
Bradyrhizobium Japonicum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Defense Responses ◽  
Plant Defense Responses ◽  
Wild Type ◽  
Enhanced Sensitivity ◽  
Viable Bacteria ◽  
Glucan Synthesis

Susceptibility of the nitrogen-fixing soybean symbiont Bradyrhizobium japonicum to inducible plant defense metabolites such as phytoalexin and H2O2, was investigated. On the wild-type strain USDA 110 the soybean phytoalexin, glyceollin, showed bacteriostatic activity. Viable bacteria isolated from intact nodules were adapted to glyceollin. H2O2 in physio­logical concentrations did not affect wild-type bacteria. B. japonicum mutants defective in the biosynthesis of cyclic β-(1→3)-(1→6)-glucans showed higher susceptibility to both phyto­alexin and H2O2

scholarly journals Enhanced Hydrogen Production from Formic Acid by Formate Hydrogen Lyase-Overexpressing Escherichia coli Strains

2005 ◽  
Vol 71 (11) ◽  
pp. 6762-6768 ◽  
Author(s):  
Akihito Yoshida ◽  
Taku Nishimura ◽  
Hideo Kawaguchi ◽  
Masayuki Inui ◽  
Hideaki Yukawa
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Production ◽  
Formic Acid ◽  
Cell Density ◽  
Type Strain ◽  
Wild Type Strain ◽  
Genetic Recombination ◽  
Large Subunit ◽  
Wild Type ◽  
Formate Hydrogen Lyase

ABSTRACT Genetic recombination of Escherichia coli in conjunction with process manipulation was employed to elevate the efficiency of hydrogen production in the resultant strain SR13 2 orders of magnitude above that of conventional methods. The formate hydrogen lyase (FHL)-overexpressing strain SR13 was constructed by combining FHL repressor (hycA) inactivation with FHL activator (fhlA) overexpression. Transcription of large-subunit formate dehydrogenase, fdhF, and large-subunit hydrogenase, hycE, in strain SR13 increased 6.5- and 7.0-fold, respectively, compared to the wild-type strain. On its own, this genetic modification effectively resulted in a 2.8-fold increase in hydrogen productivity of SR13 compared to the wild-type strain. Further enhancement of productivity was attained by using a novel method involving the induction of the FHL complex with high-cell-density filling of a reactor under anaerobic conditions. Continuous hydrogen production was achieved by maintaining the reactor concentration of the substrate (free formic acid) under 25 mM. An initial productivity of 23.6 g hydrogen h−1 liter−1 (300 liters h−1 liter−1 at 37°C) was achieved using strain SR13 at a cell density of 93 g (dry weight) cells/liter. The hydrogen productivity reported in this work has great potential for practical application.

scholarly journals Aerobic Vanillate Degradation and C1 Compound Metabolism in Bradyrhizobium japonicum

2009 ◽  
Vol 75 (15) ◽  
pp. 5012-5017 ◽  
Author(s):  
Nirinya Sudtachat ◽  
Naofumi Ito ◽  
Manabu Itakura ◽  
Sachiko Masuda ◽  
Shima Eda ◽  
...  
Keyword(s):  
Cell Growth ◽  
Bradyrhizobium Japonicum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Multiple Gene ◽  
Gene Copies ◽  
Low Concentrations ◽  
Metabolic Capability ◽  
Aromatic Degradation

ABSTRACT Bradyrhizobium japonicum, a symbiotic nitrogen-fixing soil bacterium, has multiple gene copies for aromatic degradation on the genome and is able to use low concentrations of vanillate, a methoxylated lignin monomer, as an energy source. A transcriptome analysis indicated that one set of vanA1B, pcaG1H1, and genes for C1 compound catabolism was upregulated in B. japonicum USDA110 cells grown in vanillate (N. Ito, M. Itakura, S. Eda, K. Saeki, H. Oomori, T. Yokoyama, T. Kaneko, S. Tabata, T. Ohwada, S. Tajima, T. Uchiumi, E. Masai, M. Tsuda, H. Mitsui, and K. Minamisawa, Microbes Environ. 21:240-250, 2006). To examine the functions of these genes in vanillate degradation, we tested cell growth and substrate consumption in vanA1B, pcaG1H1, and mxaF mutants of USDA110. The vanA1B and pcaG1H1 mutants were unable to grow in minimal media containing 1 mM vanillate and protocatechuate, respectively, although wild-type USDA110 was able to grow in both media, indicating that the upregulated copies of vanA1B and pcaG1H1 are exclusively responsible for vanillate degradation. Mutating mxaF eliminated expression of gfa and flhA, which contribute to glutathione-dependent C1 metabolism. The mxaF mutant had markedly lower cell growth in medium containing vanillate than the wild-type strain. In the presence of protocatechuate, there was no difference in cell growth between the mxaF mutant and the wild-type strain. These results suggest that the C1 pathway genes are required for efficient vanillate catabolism. In addition, wild-type USDA110 oxidized methanol, whereas the mxaF mutant did not, suggesting that the metabolic capability of the C1 pathway in B. japonicum extends to methanol oxidation. The mxaF mutant showed normal nodulation and N2 fixation phenotypes with soybeans, which was not similar to symbiotic phenotypes of methylotrophic rhizobia.

scholarly journals Phenotype Overlap in Xylella fastidiosa Is Controlled by the Cyclic Di-GMP Phosphodiesterase Eal in Response to Antibiotic Exposure and Diffusible Signal Factor-Mediated Cell-Cell Signaling

2013 ◽  
Vol 79 (11) ◽  
pp. 3444-3454 ◽  
Author(s):  
Alessandra A. de Souza ◽  
Michael Ionescu ◽  
Clelia Baccari ◽  
Aline M. da Silva ◽  
Steven E. Lindow
Keyword(s):  
Cell Density ◽  
Type Strain ◽  
Deletion Mutant ◽  
Wild Type Strain ◽  
Xylella Fastidiosa ◽  
Wild Type ◽  
Extrinsic Factors ◽  
Content Type ◽  
Diffusible Signal Factor ◽  
Cell Cell

ABSTRACTEal is an EAL domain protein inXylella fastidiosahomologous to one involved in resistance to tobramycin inPseudomonas aeruginosa. EAL and HD-GYP domain proteins are implicated in the hydrolysis of the secondary messenger bis-(3′-5′)-cyclic dimeric GMP (cyclic di-GMP). Cell density-dependent communication mediated by a Diffusible Signal Factor (DSF) also modulates cyclic di-GMP levels inX. fastidiosa, thereby controlling the expression of virulence genes and genes involved in insect transmission. The possible linkage of Eal to both extrinsic factors such as antibiotics and intrinsic factors such as quorum sensing, and whether both affect virulence, was thus addressed. Expression ofealwas induced by subinhibitory concentrations of tobramycin, and anealdeletion mutant was more susceptible to this antibiotic than the wild-type strain and exhibited phenotypes similar to those of anrpfFdeletion mutant blocked in DSF production, such as hypermotility, reduced biofilm formation, and hypervirulence to grape. Consistent with that, therpfFmutant was more susceptible than the wild-type strain to tobramycin. Therefore, we propose that cell-cell communication and antibiotic stress can apparently lead to similar modulations of cyclic di-GMP inX. fastidiosa, resulting in similar phenotypes. However, the effect of cell density is dominant compared to that of antibiotic stress, sinceealis suppressed by RpfF, which may prevent inappropriate behavioral changes in response to antibiotic stress when DSF accumulates.

scholarly journals Effects of Mutations of RAD50, RAD51, RAD52, and Related Genes on Illegitimate Recombination in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 142 (2) ◽  
pp. 383-391 ◽  
Author(s):  
Yasumasa Tsukamoto ◽  
Jun-ichi Kato ◽  
Hideo Ikeda
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Quantitative Analysis ◽  
Structural Analysis ◽  
Recombination Rate ◽  
Type Strain ◽  
Negative Selection ◽  
Wild Type Strain ◽  
Illegitimate Recombination ◽  
Wild Type ◽  
In The Wild

Abstract To examine the mechanism of illegitimate recombination in Saccharomyces cerevisiae, we have developed a plasmid system for quantitative analysis of deletion formation. A can1 cyh2 cell carrying two negative selection markers, the CAN1 and CYH2 genes, on a YCp plasmid is sensitive to canavanine and cycloheximide, but the cell becomes resistant to both drugs when the plasmid has a deletion over the CAN1 and CYH2 genes. Structural analysis of the recombinant plasmids obtained from the resistant cells showed that the plasmids had deletions at various sites of the CAN1-CYH2 region and there were only short regions of homology (1-5 bp) at the recombination junctions. The results indicated that the deletion detected in this system were formed by illegitimate recombination. Study on the effect of several rad mutations showed that the recombination rate was reduced by 30-, 10-, 10-, and 10-fold in the rad52, rad50, mre11, and xrs2 mutants, respectively, while in the rud51, 54, 55, and 57 mutants, the rate was comparable to that in the wild-type strain. The rad52 mutation did not affect length of homology at junction sites of illegitimate recombination.

scholarly journals The role of Zur-regulated lipoprotein A in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles in Acinetobacter baumannii

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nayeong Kim ◽  
Hyo Jeong Kim ◽  
Man Hwan Oh ◽  
Se Yeon Kim ◽  
Mi Hyun Kim ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Mutant Strain ◽  
Antimicrobial Susceptibility ◽  
Type Strain ◽  
Wild Type Strain ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Wild Type ◽  
Bacterial Morphology

Abstract Background Zinc uptake-regulator (Zur)-regulated lipoprotein A (ZrlA) plays a role in bacterial fitness and overcoming antimicrobial exposure in Acinetobacter baumannii. This study further characterized the zrlA gene and its encoded protein and investigated the roles of the zrlA gene in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles (OMVs) in A. baumannii ATCC 17978. Results In silico and polymerase chain reaction analyses showed that the zrlA gene was conserved among A. baumannii strains with 97–100% sequence homology. Recombinant ZrlA protein exhibited a specific enzymatic activity of D-alanine-D-alanine carboxypeptidase. Wild-type A. baumannii exhibited more morphological heterogeneity than a ΔzrlA mutant strain during stationary phase. The ΔzrlA mutant strain was more susceptible to gentamicin than the wild-type strain. Sizes and protein profiles of OMVs were similar between the wild-type and ΔzrlA mutant strains, but the ΔzrlA mutant strain produced 9.7 times more OMV particles than the wild-type strain. OMVs from the ΔzrlA mutant were more cytotoxic in cultured epithelial cells than OMVs from the wild-type strain. Conclusions The present study demonstrated that A. baumannii ZrlA contributes to bacterial morphogenesis and antimicrobial resistance, but its deletion increases OMV production and OMV-mediated host cell cytotoxicity.

scholarly journals FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Wei Liu ◽  
Xue Bai ◽  
Yan Li ◽  
Haikun Zhang ◽  
Xiaoke Hu
Keyword(s):  
Signal Transduction ◽  
Host Plant ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Response Regulators ◽  
Free Living ◽  
Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

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