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 130,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some mutants and stock strains of Escherichia coli K12 were sensitive to acriflavine in the presence of inorganic phosphate but were resistant to acriflavine in its absence. They mutated spontaneously to resistance to acriflavine plus phosphate. The synergistic effect of phosphate on acriflavine sensitivity was increased at high pH values. Genetic analysis suggested that the mutations occurred in the gene acrA. Electron microscopic observation suggested that the presence of acriflavine plus phosphate affected the structure of the plasma membrane and the cytoplasm under it. This structural alteration was not caused by acriflavine alone. Acridine orange plus phosphate can more effectively eliminate the plasmid F8-gal+ than acridine orange alone.
J Gen Microbiol 1975 Nov
PMID:Effect of inorganic phosphate on acridine inhibition and plasmid curing in Escherichia coli. 0 Apr 66

E. coli K12 was found to utilise both D-and L-stereoisomers of alanine as sole sources of carbon, nitrogen and energy for growth. This capability was absolutely dependent upon the possession of an active membrane-bound D-alanine dehydrogenase, and was lost by mutants in which the enzyme was defective. The Michaelis constant for the enzyme with D-alanine as substrate was 30 mM, and the pH optimum about 8.9. D-alanine was the most active substrate, L-alanine was inactive and several other D-amino acids were 10--50% as active as D-alanine. Oxidation of D-alanine was linked to oxygen via a cytochrome-containing respiratory chain. Synthesis of the dehydrogenase was induced 16 to 23-fold by incubation with D- or L-alanine, but only D-alanine was intrinsically active as an inducer. L-alanine was active either as a substrate or inducer only in t he presence of an uninhibited alanine racemase which converted it to the D-isomer. The map-location of their structural genes between ara and leu, together with other similarities, indicate that D-alanine dehydrogenase and the "alaninase" of Wijsman (1972a) are the same enzyme. Both D- and L-alanine were intrinsically active as inducers of alanine racemase synthesis. The synthesis of both D-alanine dehydrogenase and alanine racemase was found to be regulated by catabolite repression.
Mol Gen Genet 1976 Dec 08
PMID:Biochemical, genetic, and regulatory studies of alanine catabolism in Escherichia coli K12. 1 92

Mutants of Escherichia coli K12 have been isolated that grow on media containing pyruvate of proline as sole carbon sources despite the presence of 10 or 50 mM-sodium fluoroacetate. Such mutants lack either acetate kinase [ATP: acetate phosphotransferase; EC 2.7.2.1] or phosphotransacetylase [acetyl-CoA: orthophosphate acetyltransferase; EC 2.3.1.8] activity. Unlike wild-type E. coli, phosphotransacetylase mutants do not excrete acetate when growing aerobically or anaerobically on glucose; their anaerobic growth on this sugar is slow. The genes that specify acetate kinase (ack) and phosphotransacetylase (pta) activities are cotransducible with each other and with purF and are thus located at about min 50 on the E. coli linkage map. Although Pta- and Ack- mutants are greatly impaired in their growth on acetate, they incorporate [2-14C]acetate added to cultures growing on glycerol, but not on glucose. An inducible acetyl-CoA synthetase [acetate: CoA ligase (AMP-forming); EC 6.2.1.1] effects this uptake of acetate.
J Gen Microbiol 1977 Oct
PMID:The enzymic interconversion of acetate and acetyl-coenzyme A in Escherichia coli. 2 41

In order to elucidate the molecular mechanisms of Ca(2+)-dependent competence in gram-negative bacteria an attempt was made to induce the competence at room temperature in presence of a proton conductor, carbonylcyanide-m-chlorophenylhydrazone (CCCP). Escherichia coli K12 cells treated with Ca2+ at 25 degrees or 37 degrees C in presence of CCCP became permeable for transforming plasmid and transfecting DNAs and DNA-binding antibiotic actinomycin C (AmC) and rubomycin (Rm) at room temperature. The efficiencies of transformation and transfection, however, were by 1-3 orders of magnitude lower compared to cells, treated with Ca2+ at 0 degree C, though both recipients did not differ significantly in their susceptibility to AmC and Rm. Possible mechanisms of Ca2+ action in both recipient systems are discussed in terms of molecular interactions.
Mol Gen Genet 1979
PMID:Proton conductor vs. cold in induction of Ca(2+)-dependent competence in Escherichia coli. 4 13

A strain which carries a mutation conferring clorobiocin resistance and temperature sensitivity for growth was isolated from Escherichia coli K12. Genetic mapping and the molecular weight of the gene product suggest that the mutation is in the cou gene, specifying a sub-unit of DNA gyrase. Nuclear organisation and segregation and placement of septa are grossly abnormal in the mutant at 42 degrees C. RNA synthesis and initiation of DNA replication are also affected at the restrictive temperature but the rate of DNA chain elongation continues almost undisturbed.
Mol Gen Genet 1979
PMID:Isolation and characterisation of a strain carrying a conditional lethal mutation in the cou gene of Escherichia coli K12. 9 44

Uvm mutants of Escherichia coli K12 selected for defective UV reversion induction have previously been reported to differ considerably from the UV-reversion-less recA and lexA mutants with regard to survival or mutagenic response to UV, X-rays and alkylating agents. In the present study, the phenotypic characterization of uvm mutants was extended to investigate several cellular processes which also may be related to or involved in UV mutagenesis. Like recA and lexA mutations, the uvm mutations exhibit highly reduced Weigle reactivation and normal host cell reactivation of UV irradiated phage lambda. But unlike recA and lexA, the uvm mutations do not impair genetic recombination, UV induction of prophage lambda or R plasmid-mediated UV resistance and mutagenesis. These phenotypical characteristics and preliminary results of genetic mapping lend further support to the assumption that the uvm site may be a novel locus affecting, apart from the recA and lexA loci, the error-prone repair pathway in E. coli.
Mol Gen Genet 1979 Sep
PMID:Uvm mutants of Escherichia coli K12 deficient in UV mutagenesis. II. Further evidence for a novel function in error-prone repair. 16 1

The isolation and properties of a mutant of Escherichia coli K12 that is totally unable to take up and utilize gluconate are described. Genetical analysis shows this phenotype to be associated with two lesions. One phenotype, designated GntM-, is the result of a mutation in a gene co-transducible with malA; the other, designated GNTS-, is the result of a mutation in a gene (GntS) co-transducible with fdp. The GntS--phenotype differs little from that of wild-type cells, but GntM- GntS+ organisms grow on gluconate only after a prolonged lag and form a gluconate uptake system that is strongly repressed by pyruvate. Moreover, such GntM- mutants readily give rise to further mutants that form a gluconate uptake system, gluconate kinase and 6-phosphogluconate dehydratase consititutively; in partial diploids, this constitutivity is recessive to the inducible character. It is postulated that the GntM- phenotype is due to malfunction of a negative control gene gntR, and that gntS+ specifies the activity of a gluconate uptake system.
J Gen Microbiol 1975 Oct
PMID:Genes involved in the uptake and catabolism of gluconate by Escherichia coli. 17 99

An unusual Escherichia coli K12 mutant for carbamyl phosphate synthetase is described. The mutation was generated by bacteriophage MUI insertion and left a 5% residual activity of the enzyme using either ammonia or glutamine as donors. The mutation is recessive to the wild-type allele and maps at or near the pyrA gene, but the mutant requires only arginine and not uracil for growth. By a second block in the pyrB gene it was possible to shift the accumulated carbamyl phosphate to arginine biosynthesis. The Km values and the levels of ornithine activation and inhibition by UMP were normal in the mutant enzyme.
J Gen Microbiol 1976 May
PMID:Biochemical and genetic characterization of a carbamyl phosphate synthetase mutant of Escherichia coli K12. 18 Feb 36

Escherichia coli K12 cannot grow on D-arabitol, L-arabitol, ribitol or xylitol (Reiner, 1975). Using a mutant of E. coli K12 (strain 3; Sridhara et al., 1969) that can grow on L-1,2-propanediol, a second-stage mutant was isolated which can utilize D-arabitol as sole source of carbon and energy for growth. D-Arabitol is probably transported into the bacteria by the same system as that used for the transport of L-1,2-propanediol. The second-stage mutant constitutively synthesizes a new dehydrogenase, which is not present in the parent strain 3. This enzyme, whose native substrate may be D-galactose, apparently dehydrogenates D-arabitol to D-xylulose, and its structural gene is located at 68.5 +/- 1 min on the E. coli genetic map. D-Xylulose is subsequently catabolized by the enzymes of the D-xylose metabolic pathway.
J Gen Microbiol 1976 Jun
PMID:Growth on D-arabitol of a mutant strain of Escherichia coli K12 using a novel dehydrogenase and enzymes related to L-1,2-propanediol and D-xylose metabolism. 18 26

Strains of Escherichia coli K12 that contain a deletion of the adenyl cyclase gen (cya delta), required for the synthesis of cyclic adenosine-3';5' monophosphate (cAMP), grow on galactose-containing minimal medium. A mutant was isolated that grows on this medium only if cAMP is added. The mutation (designated galP20) is linked to the gal operon region as determined by both generalized transduction with bacteriophage P1 and specialized transduction with bacteriophage lambda. Studies with galP20 cya delta strains as well as gal delta (deletions of the gal operon) cya delta strains indicate that synthesis of the physiologically important transport mechanism for galactose (galactose permease) requires either cAMP or a function mission from both the galdelta strains and the galP20 strain.
Mol Gen Genet 1977 Jan 18
PMID:A gal region mutant that requires cAMP for growth on galactose in an adenyl cyclase negative (cya delta) background. 19 May 30


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