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M Chippaux

Publications and source records attributed to M Chippaux.

At least 55 records · Page 3Linked to original sources
PubMed1984

Cellobiose metabolism in Erwinia: genetic study.

The study of mutants of Erwinia specifically unable to ferment cellobiose indicates that the mutations are clustered between arg and ile on the chromosome of this organism. In vivo cloning of the genes responsible for cellobiose utilization lead to a plasmid, pBEC2, which complements all Erwinia Clb- specific mutants. When introduced into wild-type E. coli it allows this organism to use cellobiose, arbutin and salicin; it also complements bglB and bglC mutants of Escherichia coli indicating that arbutin and salicin utilization is due to the products of the pBEC2 cloned genes. From the characterization of mutants pleiotropically affected in the utilization of various carbon sources, including cellobiose, arbutin and salicin, it is proposed that the three beta-glucosides are substrates of the phosphoenolpyruvate-dependent phosphotransferase system (PTS).

Cellobiose↗
PubMed1984

Regulation of the trimethylamine N-oxide (TMAO) reductase in Escherichia coli: analysis of tor::Mud1 operon fusion.

Mud1 insertion mutants of Escherichia coli were obtained in which the lac structural genes were fused to the promoter of torA, a gene encoding the trimethylamine N-oxide (TMAO) reductase. Expression of the fusion is induced by TMAO and repressed by oxygen. However, in contrast to the nar operon which codes for the nitrate reductase structural genes, the tor::Mud1 fusion was found to be independent of the positive control exerted by the nirR gene product and not repressed by the molybdenum cofactor. The torA gene which is strongly linked to pyrF (28.3U) is different from any tor gene already described in E. coli or in Salmonella typhimurium.

Crosses, Genetic↗
PubMed1982

Involvement of a gene of the chl E locus in the regulation of the nitrate reductase operon.

A strain of E. coli carrying a Mudl insertion leading to chlorate resistance was found to lack nitrate reductase and formate dehydrogenase activities, but to synthesize b-type cytochrome constitutively. Introduction of this insertion mutation into a strain bearing a fusion between the nitrate reductase operon (chl C, chl I) and the lac structural genes resulted in the constitutive expression of the lac genes of this last fusion. Identical results were found when the Mudl was eliminated promoting a deletion in the original insertion site. This mutation was located midway between gal and aro A, at the Chl E locus. Study of a chl E strain already described revealed similar behaviour. Absence of nitrate reductase activity in these strains which constitutively express the structural genes of the nitrate reductase operon was tentatively attributed to the simultaneous lack of a cofactor of the nitrate reductase terminal enzyme, possibly cofactor Mo-X, and of a repressor of the operon.

Apoproteins↗
PubMed1982

Regulation of the nitrate reductase operon: effect of mutations in chlA, B, D and E genes.

Introduction of chlA, B or E mutant alleles into strains carrying fusions between the lac structural genes and the promoter of the nitrate reductase operon led to the partial or total constitutive expression of the fusion. Presence of chlD mutated alleles in the same strains did not result in constitutive expression of the fusion and allowed full induction by nitrate only in the presence of molybdenum. It is proposed that the molybdenum cofactor, Mo-X, of the nitrate reductase is also corepressor of the operon. The chlA, B and E genes would be involved in the biosynthesis of the X-moity. Mutations in these genes would give an altered X-moity which still binds to molybdenum but leads to a less efficient repressor complex; chlD gene would code for an enzyme inserting molybdenum in the X-moity of the cofactor. Mutations in chlD give an empty cofactor leading to a complex which permanently represses the operon unless molybdenum is added.

Escherichia coli↗
PubMed1981

Operon fusions in the nitrate reductase operon and study of the control gene nir R in Escherichia coli.

Strains carrying operon fusions between the promotor of the chl I gene and the lac structural genes were constructed. From these strains in which the expression of the lac genes is under the control of both nitrate and oxygen, spontaneous regulatory mutants were selected: (i) mutants which synthesize beta-galactosidase constitutively in anaerobiosis; (ii) mutants in which beta-galactosidase synthesis is no longer repressed by oxygen. Introduction of the nir R mutated allele into strains carrying these fusions resulted in the total loss of beta-galactosidase synthesis, confirming that nir R is a regulatory gene controlling the expression of the biosynthesis of the nitrate reductase.

Anaerobiosis↗
PubMed1981

Mutants of Escherichia coli K12 with defects in anaerobic pyruvate metabolism.

A strain of Escherichia coli with a mutation in the ana gene was shown to lack acetaldehyde dehydrogenase and alcohol dehydrogenase. The requirement of this strain for an external oxidant to grow anaerobically on glucose shows that the reduction of acetyl-CoA is the principal means of reoxidation of NADH produced during glycolysis in E. coli. Further mutants derived from the ana strain were shown to be affected in the enzymes involved in the fermentation of pyruvate (pyruvate formate-lyase, phosphotransacetylase, acetate kinase). A gene controlling acetate kinase (ackB) activity has been located at 39 min on the chromosomal map. Evidence is presented that anaerobic nitrite reduction with pyruvate involves at least the dehydrogenase subunit of the pyruvate dehydrogenase complex.

Acetates↗
PubMed1980

A mutant defective in electron transfer to nitrate in Escherichia coli K12.

A mutant of Escherichia coli K12 is described which is unable to reduce nitrate with a variety of physiological electron donors but which retains nitrate reductase activity with the artificial electron donor benzyl viologen. It is suggested that the affected gene, chlI, located close to chlC, encodes the cytochrome bNR apoprotein.

Cytochromes↗
PubMed1979

Localization and characterization of cytochromes from membrane vesicles of Escherichia coli K-12 grown in anaerobiosis with nitrate.

Cytochromes b of anaerobically nitrate-grown Escherichia coli cells are analysed. Ascorbate phenazine methosulfate distinguishes low and high potential cytochromes b. Reduction kinetics performed at 559 nm presents a very complex pattern which can be analysed assuming that at least four b-type cytochromes are present. The electron transport chain from formate to oxygen would contain a low potential cytochrome b-556, a cytochrome b-558 associated to the oxidase, and a cytochrome d as the principle oxidase. Cytochrome o is also present, but seems to be functional only at low oxygen concentrations. A cytochrome b-556 associated to nitrate reductase is shown to belong to a branch of the formate-oxidase chain. 2-N-Heptyl-4-hydroxyquinoline-N-oxide affects the reduction kinetics in a very complex way. One inhibition site is in evidence between cytochrome b-558 and cytochrome d; another between the cytochrome associated to nitrate reductase and the nitrate reductase. A third inhibition site is located in the common part of the formate-nitrate and the formate-oxidase systems. Ascorbate phenazine methosulfate is shown to donate electrons near cytochrome b-558.

Anaerobiosis↗
PubMed1978

Nitrite reduction in Escherichia coli: genetic analysis of nir mutants.

Five mutants of Escherichia coli impaired on nitrite reduction were studied. All have lost NADH-nitrite reductase activity but have retained the capacity to synthesize all or part of their cytochrome c552. Three genes, nir C, nir D, and nir E were mapped at 26, 72.5 and 49.5 min, respectively. Another gene, nir F was tentatively localized around 52 min.

Chromosome Mapping↗
PubMed1978

Laboratoire de Chimie Bactérienne C.N.R.S., Marsielle, France.

Mutants of E. coli, completely devoid of nitrite reductase activity with glucose or formate as donor were studied. Biochemical analysis indicates that they are simultaneously affected in nitrate reductase, nitrite reductase, fumarate reductase and hydrogenase activities as well as in cytochrome C552 biosynthesis. The use of an antiserum specific for nitrate reductase shows that the nitrate reductase protein is probably missing. A single mutation is responsible for this phenotype: the gene affected, nir R, is located close to tyr R i.e. at 29 min on the chromosomal map.

Escherichia coli↗