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Biomedical subjects

J Konisky

Publications and source records attributed to J Konisky.

70 records · Page 4Linked to original sources
PubMed1975

Effects of colicin Ia on transport and respiration in Escherichia coli.

Treatment of Escherichia coli with colicin Ia leads to an inhibition in the active transport of exogenously supplied proline, thiomethyl-beta-D-galactoside and potassium ion. Furthermore, the addition of colicin Ia to cells preloaded with these substances leads to their almost immediate efflux. In contrast, colicin tia treatment enhances by as much as 10-fold the level of accumulation of alpha-methyl-D-glucoside. The colicin Ia-induced stimulation of glucoside accumulation is mediated by the phosphotransferase system. Cells treated with colicin Ia exhibit an increased rate of respiration when glucose is the substrate and a decreased rate when glycerol or succinate is the substrate; The decreased rate of succinate-dependent respiration is probably due to the failure of Ia-treated cells to accumulate succinate.

Biological Transport↗
PubMed1975

Alterations in membrane function in an Escherichia coli mutant tolerant to colicins Ia and Ib.

An Escherichia coli mutant (tolI) previously shown to be tolerant to colicins Ia and Ib is defective in several functions of the bacterial cytoplasmic membrane. When compared with its parental strain, X36, whole cells of tolI show reduced rates of respiration with succinate, malate, or lactate as the substrate but near-normal rates with glucose or glycerol. Cell membrane preparations prepared from tolI cells exhibit reduced succinate and D-lactate oxidase activity but elevated levels of reduced-form nicotinamide adenine dinucleotide (NADH) oxidase. tolI cells have reduced levels of succinate and D-lactate dehydrogenase but normal levels of NADH dehydrogenase. Glycerol-grown tolI cells and membrane vesicles prepared from such cells are defective in the active transport of several amino acids and thiomethyl-beta-D-galactoside; however, they accumulate higher levels of alpha-methylglucoside when compared with X36 whole cells or vesicles. Although tolI cells adsorb less colicin Ia at high colicin concentrations than do X36 cells, it is shown that the adsorption of an Ia molecule to tolI cells has a lower probability of eliciting cell death than does Ia adsorption to strain X36 cells. It is concluded that a single mutation can lead to an alteration in several aspects of cytoplasmic membrane function and colicin I sensitivity.

Acetates↗
PubMed1974

Studies on the regulation of colicin Ib synthesis: replication of the Col Ib-P9 plasmid during colicin induction.

The Col Ib-P9 plasmid content of colicinogenic cells has been measured by both sedimentation analysis of cleared lysates and by deoxyribonucleic acid hybridization to purified Col Ib-P9 factor deoxyribonucleic acid. The results show an independence between mitomycin C-induced colicin synthesis and Col Ib-P9 replication. In addition, the ratio of the various molecular configurations (i.e., covalently closed circles or open circles) of the Col Ib-P9 plasmid does not change upon induction of colicin synthesis. Heat treatment of a colicinogenic strain carrying a thermosensitive dnaB mutation on the bacterial chromosome leads to complete inhibition of Col Ib-P9 plasmid replication and the simultaneous induction of colicin Ib synthesis in all cells of the colicinogenic population. These studies rule out mechanisms or regulation of colicin Ib synthesis based on the induced replication of the Col Ib-P9 plasmid. Our studies show that in a Col Ib-P9 colicinogenic population there is, on the average, one plasmid per cell.

Colicins↗
PubMed1974

Isolation and characterization of an Escherichia coli mutant tolerant to colicins Ia and Ib.

Two classes of spontaneous colicin I insensitive mutants of Escherichia coli have been isolated. The first class (called cir) has lost its ability to adsorb either colicin Ia or Ib, maps at 41 min on the E. coli genetic map, and retains sensitivity to all other colicins tested. The cir phenotype is probably due to an alteration in the colicin I receptor. The second class of mutant (called tolI) retains full capacity to adsorb [(125)I]colicin I and, therefore, represents the isolation of a mutant tolerant to colicin I. The tolI mutant is sensitive to all other colicins tested and has a map location of 89-1 min. The tolI mutant grows with a reduced mass yield when glucose is used as a carbon source and cannot utilize succinate or acetate for growth. The tolI mutant shows a reduced sensitivity to sodium azide and phenethylalcohol. It is suggested that tolI is deficient in some aspect of aerobic metabolism which must be operative for colicin I sensitivity.

Acetates↗
PubMed1973

Electron microscopy of colicin I-producing cells.

Electron microscope examination of mitomycin C-induced strains of Escherichia coli colicinogenic for colicins Ia or Ib reveals particles of approximately 15 to 20 nm in diameter associated with the cell surface. Such structures are not present on uninduced colicinogenic strains nor on a mitomycin C-treated non-colicinogenic strain. In contrast to wild-type colicinogenic strains, induction of a colicinogenic strain known to be lacking the specific colicin I receptor was shown to result in the release of colicin activity into the cell medium. Examination of such induced mutants by electron microscopy showed their cell surfaces to be free of the particles observed on the wild-type strain. The cell medium of such induced mutant strains contained large numbers of particles of similar size and shape to those found on the surface of induced colicinogenic wild-type strains.

Binding Sites↗
PubMed1971

Specific inactivation of 16S ribosomal RNA induced by colicin E3 in vivo.

Treatment of sensitive Escherichia coli cells with colicin E3 leads to inactivation of 30S ribosomal subunits. In vitro reconstitution of 30S subunits indicates that the E3-induced defect lies solely in the 16S RNA. 16S RNA from E3-treated cells lacks several T(1) RNase oligonucleotides of normal 16S RNA, including the one from the 3'-end of the 16S RNA, as analyzed by the fingerprint technique of Sanger. An RNA fragment about 50 nucleotides long has been isolated from E3-treated cells. This RNA contains the original 3'-terminal oligonucleotide and other oligonucleotides missing in the E3-16S RNA. The results show that colicin E3 treatment causes the cleavage of 16S RNA at a specific position near the 3'-terminus.

Alkaline Phosphatase↗
PubMed1968

Interaction of colicins with bacterial cells. IV. Immunity breakdown studied with colicins Ia and Ib.

Colicinogenic cells are immune to the lethal effect of the colicin which they produce. In the presence of very high concentrations of colicin, however, colicinogenic cells are no longer immune to the homologous colicin. This phenomenon, immunity breakdown, was studied with colicins Ia and Ib. The biochemical effects of colicin Ib on Escherichia coli were studied with a standard noncolicinogenic strain. At multiplicities of about 10 or higher, colicin Ib inhibited incorporation of leucine into protein and incorporation of (32)P-inorganic phosphate into deoxyribonucleic acid and ribonucleic acid by more than 95%. Under the same conditions, (32)P incorporation into phospholipid and nucleotide fractions was inhibited only partially (about 80 and 60%, respectively). Inhibition of (32)P incorporation into the terminal phosphorus of adenosine triphosphate was also considerably less than that of macromolecular synthesis (50 to 60%). (32)P incorporation into the nonnucleotide organic phosphate fraction was not inhibited. Respiration was not affected. Colicin Ia showed the same biochemical effects as colicin Ib. A mutant of an Ib-colicinogenic E. coli strain selected for resistance to low concentrations of colicin Ia was shown to be resistant to high concentrations of homologous colicin Ib, whereas the parent Ib-colicinogenic strain is sensitive to high concentrations of colicin Ib. This mutant lost its specific receptors for colicin Ib. Moreover, the biochemical effects of high concentrations of colicin Ib on Ib-colicinogenic cells during immunity breakdown were similar to the effects found in sensitive cells exposed to low concentrations of the same colicin. It is concluded that the killing of colicinogenic cells in the presence of high concentrations of homologous colicin is indeed caused by the homologous colicin molecules.

Adenosine Triphosphate↗