scholarly journals Multicopy Vectors Carrying the Klebsiella pneumoniae nifA Gene Do Not Enhance the Nodulation Competitiveness of Sinorhizobium meliloti on Alfalfa

1998 ◽  
Vol 11 (8) ◽  
pp. 839-842 ◽  
Author(s):  
Pieter van Dillewijn ◽  
Francisco Martínez-Abarca ◽  
Nicolás Toro
Keyword(s):  
Klebsiella Pneumoniae ◽  
Sinorhizobium Meliloti ◽  
Nodulation Competitiveness ◽  
Nifa Gene

It has been reported that Sinorhizobium meliloti strains harboring IncQ and IncP multicopy vectors containing constitutively expressed Klebsiella pneumoniae nifA exhibit an increase in nodulation competitiveness on alfalfa (J. Sanjuan and J. Olivares, Mol. Plant-Microbe Interact. 4:365–369, 1991). In our efforts to understand the mechanisms involved, in this work, we have found that the observed enhancement on nodulation competitiveness by IncQ derivatives carrying K. pneumoniae nifA was not dependent on the plasmid-borne nifA activity but on the sensitivity of nonresistant strains to the streptomycin carried over from growth cultures. Furthermore, it was also determined that the nifA of K. pneumoniae on an IncP vector does not have an effect on competitiveness.

scholarly journals Identification of Genes in the RosR Regulon ofRhizobium etli

2000 ◽  
Vol 182 (6) ◽  
pp. 1706-1713 ◽  
Author(s):  
Mark A. Bittinger ◽  
Jo Handelsman
Keyword(s):  
Cell Surface ◽  
Sinorhizobium Meliloti ◽  
Sequence Similarity ◽  
Surface Characteristics ◽  
Nucleotide Sequence Analysis ◽  
Plant Host ◽  
Glucuronidase Activity ◽  
Nodulation Competitiveness ◽  
Mutant Derivative ◽  
Mass Mating

ABSTRACT RosR is a determinant of nodulation competitiveness and cell surface characteristics of Rhizobium etli and has sequence similarity to a family of transcriptional repressors. To understand how RosR affects these phenotypes, we mutagenized a rosR mutant derivative of R. etli strain CE3 with a mini-Tn5 that contains a promoterless gusA gene at one end, which acts as a transcriptional reporter. Using a mass-mating technique, we introduced rosR into each mutant in trans and screened for mutants that expressed different levels of β-glucuronidase activity in the presence and absence ofrosR. A screen of 18,000 mutants identified 52 insertions in genes negatively regulated by RosR and 1 insertion in a gene positively regulated by RosR. Nucleotide sequence analysis of the regions flanking the insertions suggests that RosR regulates genes of diverse function, including those involved in polysaccharide production and in carbohydrate metabolism and those in a region containing sequence similarity to virC1 and virD3 fromAgrobacterium tumefaciens. Two of the mutants produced colonies with altered morphology and were more competitive in nodulation than was CE3ΔrosR, the rosRparent. One mutant that contained an insertion in a gene with similarity to exsH of Sinorhizobium melilotidid not nodulate the plant host Phaseolus vulgaris withoutrosR. These results indicate that RosR directly or indirectly influences expression of diverse genes in R. etli, some of which affect the cell surface and nodulation competitiveness.

Role of the nifA gene product in the regulation of nif expression in Klebsiella pneumoniae

Nature ◽  
1981 ◽  
Vol 294 (5843) ◽  
pp. 776-778 ◽  
Author(s):  
V. Buchanan-Wollaston ◽  
M. C. Cannon ◽  
J. L. Beynon ◽  
F. C. Cannon
Keyword(s):  
Klebsiella Pneumoniae ◽  
Gene Product ◽  
Nifa Gene

Disruption of nifA Gene Influences Multiple Cellular Processes in Sinorhizobium meliloti

2007 ◽  
Vol 34 (9) ◽  
pp. 783-789 ◽  
Author(s):  
Ziying Gong ◽  
Jiabi Zhu ◽  
Guanqiao Yu ◽  
Huasong Zou
Keyword(s):  
Sinorhizobium Meliloti ◽  
Cellular Processes ◽  
Nifa Gene

Early production of rhizopine in nodules induced bySinorhizobium melilotistrain L5-30

2001 ◽  
Vol 47 (2) ◽  
pp. 165-171 ◽  
Author(s):  
K Heinrich ◽  
M H Ryder ◽  
P J Murphy
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Fold Increase ◽  
Gas Chromatography Mass Spectrometry ◽  
Post Inoculation ◽  
Infection Threads ◽  
Nodulation Competitiveness ◽  
Meliloti Strain ◽  
Early Production ◽  
Early Effects

The rhizopine L-3-O-methyl-scyllo-inosamine (3-O-MSI) is metabolized by approximately 10% of the strains of Rhizobium leguminosarum bv. viciae and Sinorhizobium meliloti. Rhizopine strains enjoy a substantial competitive advantage in nodulation, which is manifest before 14 days post-inoculation, implying that rhizopine is produced before this time. We were able to detect this compound in the roots of alfalfa (Medicago sativum L. cv. Hunter River) four days after germination (six days post-infection) with S. meliloti strain L5-30 by gas chromatography-mass spectrometry (GC-MS). At four days, nodules were not visible, and the concentration of rhizopine was extremely low, estimated at 67 pg/gfw (picograms/gram fresh weight). The amount increased gradually but remained low until 16 days, when there was a 50-fold increase from day four, by which time nodules were well established. This pattern of synthesis is consistent with previous studies indicating that rhizopine synthesis is regulated by nifA/ntrA regulatory genes, which are maximally expressed in bacteroids at the onset of nitrogen fixation. However, the low level of rhizopine synthesis must be responsible for the early effects on competition for nodulation. Production of rhizopine at this time most likely results from micro-aerobic induction of mos genes in free-living bacteria, either in the infection threads or in the rhizosphere.Key words: Medicago sativum, nodulation competitiveness, Rhizobium, rhizopine, Sinorhizobium meliloti.

Regulation of nitrogen metabolism genes by nifA gene product in Klebsiella pneumoniae

Nature ◽  
1983 ◽  
Vol 301 (5898) ◽  
pp. 307-313 ◽  
Author(s):  
David W. Ow ◽  
Frederick M. Ausubel
Keyword(s):  
Klebsiella Pneumoniae ◽  
Gene Product ◽  
Nitrogen Metabolism ◽  
Nifa Gene

scholarly journals Involvement of the SmeAB Multidrug Efflux Pump in Resistance to Plant Antimicrobials and Contribution to Nodulation Competitiveness in Sinorhizobium meliloti

2011 ◽  
Vol 77 (9) ◽  
pp. 2855-2862 ◽  
Author(s):  
Shima Eda ◽  
Hisayuki Mitsui ◽  
Kiwamu Minamisawa
Keyword(s):  
Antimicrobial Resistance ◽  
Sinorhizobium Meliloti ◽  
Efflux Pump ◽  
Major Facilitator Superfamily ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Content Type ◽  
Multidrug Efflux Pumps ◽  
Nodulation Competitiveness ◽  
Major Facilitator

ABSTRACTThe contributions of multicomponent-type multidrug efflux pumps to antimicrobial resistance and nodulation ability inSinorhizobium melilotiwere comprehensively analyzed. Computational searches identified genes in theS. melilotistrain 1021 genome encoding 1 pump from the ATP-binding cassette family, 3 pumps from the major facilitator superfamily, and 10 pumps from the resistance-nodulation-cell division family, and subsequently, these genes were deleted either individually or simultaneously. Antimicrobial susceptibility tests demonstrated that deletion of thesmeABpump genes resulted in increased susceptibility to a range of antibiotics, dyes, detergents, and plant-derived compounds and, further, that specific deletion of thesmeCDorsmeEFgenes in a ΔsmeABbackground caused a further increase in susceptibility to certain antibiotics. Competitive nodulation experiments revealed that thesmeABmutant was defective in competing with the wild-type strain for nodulation. The introduction of a plasmid carryingsmeABinto thesmeABmutant restored antimicrobial resistance and nodulation competitiveness. These findings suggest that the SmeAB pump, which is a major multidrug efflux system ofS. meliloti, plays an important role in nodulation competitiveness by mediating resistance toward antimicrobial compounds produced by the host plant.

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