Guanylate kinase from Escherichia coli B.
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Cations↗
Biomedical subjects
M P Oeschger
Publications and source records attributed to M P Oeschger.
Ideal target organism for quantitative bactericidal assays.
We have developed a target organism which permits quantitative bactericidal assays. The organism is an Escherichia coli mutant which cannot grow at the temperature of the assay (37 degrees C), but retains full colony-forming potential for subsequent quantitation at 25 degrees C. We show that quantitative data on the bactericidal capacity of polymorphonuclear leukocytes and alveolar macrophages can be obtained when this mutant is used as a target. The procedure used to generate the strain is described in detail and should be applicable to many bacterial species. Characterization of the properties of the mutant indicates that it has a strong potential for use in other in vivo and in vitro investigations of host responses to microbial invasion.
Animals↗
Rich culture medium for the radiochemical labeling of proteins and nucleic acids.
Yeast extract was treated with tyrosine decarboxylase and used to prepare a rich, complex medium virtually free of tyrosine. The medium supported maximal growth rates for Escherichia coli prototrophs, as well as for defined and undefined auxotrophs. It has made possible the efficient radiochemical labeling of cells growing optimally in complex medium and the characterization of mutants with undefined requirements. Similarly prepared media may be useful for the study of fastidious organisms and organisms for which no defined medium has been described.
Amino Acids↗
In vivo titration of araC protein.
The requirement for araC protein in the induction of the araBAD operon was investigated. Strains of Escherichia coli carrying an araC(Am) mutation and temperature-sensitive amber suppressors were used to vary the intracellular level of araC protein. The levels of araC protein studied ranged from 0.007 to 1.8 times the normal amount. The results indicate that the normal level of araC protein is just sufficient to provide maximal expression of the araBAD operon.
Arabinose↗
A temperature-sensitive suppressor enabling the manipulation of the level of individual proteins in intact cells.
A temperature-sensitive suppressor strain of E. coli has been isolated and characterized. The properties of the mutant indicate a strong potential for its use in biochemical and genetic work. In particular, the mutant makes possible the variation of the intracellular concentration of selected protein, permitting an evaluation of its role in cell growth and biochemistry. The mutant also permits the selective radiochemical labeling of proteins in vivo for in vitro identification and analysis. The utilization of the mutant for these and other applications is discussed.
Bacterial Proteins↗
Regulation of RNA polymerase synthesis in Escherichia coli: a mutant unable to synthesize the enzyme at 43 degrees.
We report the isolation of a mutant of E. coli in which the capacity to synthesize RNA polymerase (EC 2.7.7.6) (the beta and beta' subunits) is rapidly lost at 43 degrees. The mutation has no effect on the stability or activity of the polymerase itself. The mutation is recessive and is closely linked to the rif locus (the structural gene for the beta subunit). Using strains carrying the mutation, we have shown that polymerase is present in excess in rapidly growing E. coli cells.
Coliphages↗