Papers by Claudine Elmerich
Http Dx Doi Org 10 1094 Mpmi 1998 11 3 177, Feb 19, 2007
Genetic complementation of a spontaneous mutant, impaired in flocculation, Congo red binding, and... more Genetic complementation of a spontaneous mutant, impaired in flocculation, Congo red binding, and colonization of root surface, led to the identification of a new regulatory gene in Azospirillum brasilense Sp7, designated flcA. The deduced amino acid sequence of flcA shared high similarity with a family of transcriptional activators of the LuxR-UhpA family. The most significant match was with the AgmR protein, an activator for glycerol metabolism in Pseudomonas aeruginosa. Derivatives of Sp7 resulting from site-directed Tn5 mutagenesis in the flcA coding sequence were constructed by marker exchange. Characterization of the resulting mutant strains showed that flcA controls the production of capsular polysaccharides, the flocculation process in culture, and the colonization of the root surface of wheat. This study provides new information on the genetic control of the mechanism of plant root colonization by Azospirillum.
Molecular Microbiology, Aug 1, 1991
The nucleotide sequence of a 1 kb fragment upstream of Azorhizobium cauHnodans fixL was establish... more The nucleotide sequence of a 1 kb fragment upstream of Azorhizobium cauHnodans fixL was established. An open reading frame of 744 bp was identified as a ffxK homologue. A kanamycin cartridge was inserted Into the cloned fixK-iike gene and recombined Into the host genome. The resulting mutant was Nir Fix" suggesting that FixK was required for nitrogen fixation both in symbiotic conditions and in the freeliving state. Using a pfixK-lacZ fusion, the FixLJ products were shown to control the expression of fixK. Using a p/i/M-/acZfusion, the FixK product was shown to regulate positively the transcription of nifA in bacteria grown in the free-living state. In addition, a double ntrC-fixL mutant was constructed and was shown to be completely devoid of nitrogenase activity. A model of regulation, based on these data, is presented and might explain the unusual ability of A. cauiinodans to fix nitrogen both under symbiotic conditions and in the free-living state.
Mol Gen Genet, 1998
This work reports the characterisation of the Azorhizobium caulinodans amtB gene, the deduced pro... more This work reports the characterisation of the Azorhizobium caulinodans amtB gene, the deduced protein sequence of which shares similarity to those of several ammonium transporters. amtB is located downstream from glnK, a glnB-like gene. It is cotranscribed with glnK from an NtrC- and sigma54-dependent promoter. glnK and amtB insertion mutant strains have been isolated. Methylammonium uptake was assayed in these strains and in other mutant strains in which the regulation of nitrogen metabolism is impaired. Our data suggest that the AmtB protein is an ammonium transporter, which is mainly regulated by NtrC in response to nitrogen availability.
Nitrogen Fixation: Origins, Applications, and Research Progress, 2007
... Because the conversion of IEth to IAAld is a reversible reaction, a storage role for IEth in ... more ... Because the conversion of IEth to IAAld is a reversible reaction, a storage role for IEth in IAA biosynthesis was proposed. IAM was detected neither as an endogenous constituent nor as a metabolite of 3H-Trp, and cultures did not convert IAM to 14C-IAA (Ernstsen et al., 1987). ...
de Bruijn/Molecular Microbial Ecology of the Rhizosphere, 2013
deBruijn/Biological Nitrogen Fixation, 2015
Microbiology (Reading, England), 2003
The Pseudomonas stutzeri strain A1501 (formerly known as Alcaligenes faecalis) fixes nitrogen und... more The Pseudomonas stutzeri strain A1501 (formerly known as Alcaligenes faecalis) fixes nitrogen under microaerobic conditions in the free-living state and colonizes rice endophytically. The authors characterized a region in strain A1501, corresponding to most of the nif genes and the rnf genes, involved in electron transport to nitrogenase in Rhodobacter capsulatus. The region contained three groups of genes arranged in the same order as in Azotobacter vinelandii: (1) nifB fdx ORF3 nifQ ORF5 ORF6; (2) nifLA-rnfABCDGEF-nifY2/nafY; (3) ORF13 ORF12-nifHDK-nifTY ORF1 ORF2-nifEN. Unlike in A. vinelandii, where these genes are not contiguous on the chromosome, but broken into two regions of the genome, the genes characterized here in P. stutzeri are contiguous and present on a 30 kb region in the genome of this organism. Insertion mutagenesis confirmed that most of the nif and the rnf genes in A1501 were essential for nitrogen fixation. Using lacZ fusions it was found that nif and rnf gene ...
Current Plant Science and Biotechnology in Agriculture, 2005
Current Plant Science and Biotechnology in Agriculture, 2005
Virology, 1982
A temperate bacteriophage, forming plaques on Azospirillum lipoferum strain Br17, was isolated fr... more A temperate bacteriophage, forming plaques on Azospirillum lipoferum strain Br17, was isolated from Brazilian soil samples. The phage morphology as revealed by electron microscopy showed an icosahedral head of 56 nm and a tail of 250 nm, to which six spikes are attached. The ...
Research in Microbiology, 2002
Pseudomonas aeruginosa strains that grow on crude oil as the sole source of carbon and energy wer... more Pseudomonas aeruginosa strains that grow on crude oil as the sole source of carbon and energy were isolated from an environment in Morocco polluted by petroleum refinery effluents. The twenty isolates grew on saturated alkanes from C12 to C22. Three of the isolates were also able to grow on low molecular weight C6 to C10 n-alkanes, but the other 17 strains were not. The strains were tested for alkB and alkB-related genes encoding alkane-1-monooxygenase (alkane hydroxylase). Oligonucleotide primers specific for the alkB gene of strain P. putida (GPo1) and for the alkB1 and alkB2 genes of P. aeruginosa strain PAO1 allowed amplification from the P. aeruginosa isolates of fragments similar to alkB1 and alkB2 genes of strain PAO1. Only 3 strains carried an alkB gene very similar to that of strain GPo1, and these strains were the same ones that could utilise C6 to C10 n-alkanes. 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.
Proceedings of the National Academy of Sciences, 2008
The capacity to fix nitrogen is widely distributed in phyla of Bacteria and Archaea but has long ... more The capacity to fix nitrogen is widely distributed in phyla of Bacteria and Archaea but has long been considered to be absent from the Pseudomonas genus. We report here the complete genome sequencing of nitrogen-fixing root-associated Pseudomonas stutzeri A1501. The genome consists of a single circular chromosome with 4,567,418 bp. Comparative genomics revealed that, among 4,146 protein-encoding genes, 1,977 have orthologs in each of the five other Pseudomonas representative species sequenced to date. The genome contains genes involved in broad utilization of carbon sources, nitrogen fixation, denitrification, degradation of aromatic compounds, biosynthesis of polyhydroxybutyrate, multiple pathways of protection against environmental stress, and other functions that presumably give A1501 an advantage in root colonization. Genetic information on synthesis, maturation, and functioning of nitrogenase is clustered in a 49-kb island, suggesting that this property was acquired by lateral gene transfer. New genes required for the nitrogen fixation process have been identified within the nif island. The genome sequence offers the genetic basis for further study of the evolution of the nitrogen fixation property and identification of rhizosphere competence traits required in the interaction with host plants; moreover, it opens up new perspectives for wider application of root-associated diazotrophs in sustainable agriculture. genome sequencing ͉ root-associated diazotroph
Molecular Plant-Microbe Interactions, 1998
Genetic complementation of a spontaneous mutant, impaired in flocculation, Congo red binding, and... more Genetic complementation of a spontaneous mutant, impaired in flocculation, Congo red binding, and colonization of root surface, led to the identification of a new regulatory gene in Azospirillum brasilense Sp7, designated flcA. The deduced amino acid sequence of flcA shared high similarity with a family of transcriptional activators of the LuxR-UhpA family. The most significant match was with the AgmR protein, an activator for glycerol metabolism in Pseudomonas aeruginosa. Derivatives of Sp7 resulting from site-directed Tn5 mutagenesis in the flcA coding sequence were constructed by marker exchange. Characterization of the resulting mutant strains showed that flcA controls the production of capsular polysaccharides, the flocculation process in culture, and the colonization of the root surface of wheat. This study provides new information on the genetic control of the mechanism of plant root colonization by Azospirillum.
Molecular Microbiology, 1991
The nucleotide sequence of a 1 kb fragment upstream of Azorhizobium cauHnodans fixL was establish... more The nucleotide sequence of a 1 kb fragment upstream of Azorhizobium cauHnodans fixL was established. An open reading frame of 744 bp was identified as a ffxK homologue. A kanamycin cartridge was inserted Into the cloned fixK-iike gene and recombined Into the host genome. The resulting mutant was Nir Fix" suggesting that FixK was required for nitrogen fixation both in symbiotic conditions and in the freeliving state. Using a pfixK-lacZ fusion, the FixLJ products were shown to control the expression of fixK. Using a p/i/M-/acZfusion, the FixK product was shown to regulate positively the transcription of nifA in bacteria grown in the free-living state. In addition, a double ntrC-fixL mutant was constructed and was shown to be completely devoid of nitrogenase activity. A model of regulation, based on these data, is presented and might explain the unusual ability of A. cauiinodans to fix nitrogen both under symbiotic conditions and in the free-living state.
MGG Molecular & General Genetics, 1985
... The characterization of the cloned nif genes was not explored fully, though it was ... Appl E... more ... The characterization of the cloned nif genes was not explored fully, though it was ... Appl Environ Microbiol 45 : 711 713 Elmerich C (1984) Molecular biology and ecology of ... M, Regensburgen B, Hennecke H (1983) In Rhizobium japonicum the nitrogenase gene nifH and nifDK ...
MGG Molecular & General Genetics, 1987
Deletions and Tn5 insertions were obtained in a cloned 10kb BamHI--BglII fragment carrying the ni... more Deletions and Tn5 insertions were obtained in a cloned 10kb BamHI--BglII fragment carrying the nifHDKE region of Rhizobium ORS571 and were recombined into the host genome. Genetic analysis of the mutants, comparison of polypeptides synthesized under conditions of repression and depression of Nz fixation, and biochemical complementation of crude extracts were performed. All Nif-mutants were also Fix-. Three transcription units were identified, nifItDK, nifE and a new n/f locus adjacent to nifE; no n/f locus was found in the immediate vicinity upstream of nifH. Fifteen polypeptides synthesized under conditions of N2 fixation were characterized by twodimensional gel eleetrophoresis. Ten of them are likely to be nif products and polypeptides encoded by nifH, nifD, nifK and tentatively nifE were identified. Physiological and biochemical evidence for the functioning of the second copy of nifH is reported. Nitrogenase component 2 synthesized by this copy could not be differentiated from component 2 synthesized in the wild-type strain. When the function of nifH copy 1 was abolished, the amount of component 2 synthesized was about 30% of that synthesized in the wild-type strain.
Molecular Genetics and Genomics, 2005
Regulation of NifA activity in Azospirillum brasilense depends on GlnB (a PII protein), and it wa... more Regulation of NifA activity in Azospirillum brasilense depends on GlnB (a PII protein), and it was previously reported that the target of GlnB activity is the N-terminal domain of NifA. Furthermore, mutation of the Tyr residue at position 18 in the N-terminal domain resulted in a NifA protein that did not require GlnB for activity under nitrogen fixation conditions. We report here that a NifA double mutant in which the Tyr residues at positions 18 and 53 of NifA N-were simultaneously replaced by Phe (NifA-Y1853F) displays high nitrogenase activity, which is still regulatable by ammonia, but not by GlnB. The yeast two-hybrid technique was used to investigate whether GlnB can physically interact with wild-type and mutant NifA proteins. GlnB was found to interact directly with the N-terminal GAF domain of wild-type NifA, but not with its central or C-terminal domain. GlnB could still bind to the single NifA mutants Y18F and Y53F. In contrast, no interaction was detected between GlnB and the double mutant NifA-Y18/53F or between GlnB and NifA-Y43.
MGG Molecular & General Genetics, 1993
A 7.1 kb EcoRI fragment from Azospirillum brasilense, that hybridized with a probe carrying the n... more A 7.1 kb EcoRI fragment from Azospirillum brasilense, that hybridized with a probe carrying the ntrBC genes from Bradyrhizobiumjaponicum, was cloned.
MGG Molecular & General Genetics, 1988
The fast growing strain, Azorhizobium caulinodans ORS571, isolated from stem nodules of the tropi... more The fast growing strain, Azorhizobium caulinodans ORS571, isolated from stem nodules of the tropical legume Sesbania rostrata, can grow in the free-living state at the expense of molecular nitrogen. Five point mutants impaired in nitrogen fixation in the free-living state have been complemented by a plasmid containing the cloned fix-ABC region of strain ORS571. Genetic analysis of the mutants showed that one was impaired in fixC, one in fixA and the three others in a new gene, located upstream from fixA and designated nifO. Site-directed Tn5 mutagenesis was performed to obtain Tn5 insertions in fixB and fixC. The four genes are required for nitrogen fixation both in the free-living state and under symbiotic conditions. The nucleotide sequence of nifO was established. The gene is transcribed independently of fixA and does not correspond to fixX, recently identified in Rhizobium meliloti and R. leguminosarum. Biochemical analysis of the five point mutants showed that they synthesized normal amounts of nitrogenase components. It is unlikely that fixA, fixC and nifO are involved in electron transport to nitrogenase. FixC could be required for the formation of a functional nitrogenase component 2.
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Papers by Claudine Elmerich