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E Juni

Publications and source records attributed to E Juni.

8 recordsLinked to original sources
PubMed1979

Properties of mutants of Escherichia coli lacking malic dehydrogenase and their revertants.

Mutants of Escherichia coli lacking malic dehydrogenase activity (mdh) were incapable of growth on acetate", succinate- or malate/mineral medium. Revertants of mdh strains which had regained the ability to grow on C4-dicarboxylic acids could be divided into two distinct classes. One type of revertant had regained the ability to synthesize functional malic dehydrogenase. The other type of revertant still lacked malic dehydrogenase activity but possessed a suppressor mutation which altered the regulation of the synthesis or activity of the C4-dicarboxylic acid transport system, resulting in increased C4-dicarboxylic acid transport activity. This latter class of revertants apparently synthesized oxalacetate from malate via the sequential actions of the NAD-linked malic enzyme, phosphoenolpyruvate synthetase, and phosphoenolpyruvate carboxylase. Evidence has been presented that is consistent with the hypothesis that oxalacetate is the inducer of the C4-dicarboxylic acid transport system. The inability of mutants lacking malic dehydrogenase to grow with a C4-dicarboxylic acid as the carbon source can be attributed to the difficulty such mutants have in synthesizing oxalacetate.

Escherichia coli↗
PubMed1978

Utilization of oxalacetate by Acinetobacter calcoaceticus: evidence for coupling between malic enzyme and malic dehydrogenase.

Growth of Acinetobacter calcoaceticus strain BD413 in malate-mineral medium resulted in the excretion of large quantities of oxalacetate. Malate was virtually depleted by the time the cell density reached 60% of its final value; most of the remaining growth took place at the expense of oxalacetate. Experiments in which oxalacetate was used as the initial substrate showed that pyruvate was not utilized until most of the oxalacetate disappeared. The generation time for growth on malate or oxalacetate was approximately 40 min; the generation time for growth on pyruvate was 62 min, which implies that pyruvate transport may be rate limiting. Oxalacetate and pyruvate, however, supported approximately the same growth yield. These observations suggested that the first step in the utilization of oxalacetate as an energy source consisted of an enzymatic decarboxylation of the keto acid to pyruvate and CO(2). Three enzyme reactions that carry out this decarboxylation have been detected in extracts of A. calcoaceticus. The first, which functioned maximally at pH 4.8, was attributable to the oxalacetate decarboxylase activity of oxidized diphosphopyridine nucleotide-malic enzyme. The second and third, which functioned in the neutral pH range, resulted from coupling of oxidized diphosphopyridine nucleotide-malic enzyme to reduced diphosphopyridine nucleotide-dependent malic dehydrogenase, and oxidized triphosphopyridine nucleotide-malic enzyme to a reduced triphosphopyridine nucleotide-dependent malic dehydrogenase. The efficiency of these coupled reactions was high enough so that the overall reaction could be physiologically significant.

Acinetobacter↗
PubMed1977

Unusual effects of penicillin G and chloramphenicol on the growth of Moraxella osloensis.

Growth of exponential-phase liquid cultures of Moraxella osloensis was inhibited by 0.5 U of penicillin G per ml. For this organism, low concentrations of penicillin acted primarily in a bacteriostatic rather than in a bactericidal manner. At higher concentrations of penicillin some killing did take place, but the rate of killing was rather slow and appeared to be independent of penicillin concentration. Microscopic observation of cells from penicillin-treated cultures showed little or no cellular swelling or lysis. The total cell count did not decrease significantly during 6 h of incubation in 5,000 U of penicillin per ml. The rates of respiration, nucleic acid synthesis, and protein synthesis were not affected by the presence of penicillin. Attempts to counteract the bactericidal action of high concentrations of penicillin with growth inhibitory concentrations of chloramphenicol were unsuccessful, since chloramphenicol itself was more bactericidal than penicillin for M. osloensis.

Bacterial Proteins↗
PubMed1977

Identification of Neisseria gonorrhoeae by genetic transformation: a clinical laboratory evaluation.

Transformation of a Neisseria gonorrhoeae auxotroph (uracil and arginine deficient) to prototrophy was attempted with wild-type deoxyribonucleic acid from 71 random clinical N. gonorrhoeae cultures. Of these 71 cultures, 97.1% transformed the nutritionally deficient mutant to prototrophy. The procedure was reliable and economical and offered several distinct advantages over other methods used for the confirmation of N. gonorrhoeae.

Neisseria gonorrhoeae↗
PubMed1977

Simple method for distinguishing gonococcal colony types.

Gonococcal colony types can be distinguished by a new procedure that makes use of a dissecting microscope with a concave mirror and a fluorescent lamp. Critical adjustment of the mirror angle results in illumination similar to that obtained in the dark-field microscope. When the concave mirror is set at a certain angle, colonies of the lenticular types 1 and 2 refract the light coming through them in such a way that an edge of the microscope stage is focused in each colony. By contrast, colonies of types 3 and 4, which are relatively flat, fail to refract incident light. Although distinguishable from each other by differences in color, type 3 and 4 colonies do not display the focusing effect typical for type 1 and 2 colonies and appear uniformly illuminated. This new technique permits the rapid identification and isolation of even a single type 1 or 2 colony in a field of type 3 or 4 colonies, making it possible to obtain and maintain competent colonies (type 1 or 2) for the genetic transformation assay for Neisseria gonorrhoeae strain identification as well as for other purposes.

Genetic Variation↗
PubMed1976

Genetic Transformation as a tool for detection of Neisseria gonorrhoeae.

A rapid method for the detection of Neisseria gonorrhoeae, making use of the ability of deoxyribonucleic acid samples from clinically isolated strains of this organism to transform nutritional mutants of a particular strain of N. gonorrhoeae, has been described. In addition to using isolated cultures, transforming deoxyribonucleic acid can be obtained directly from the material that adheres to swabs of the cervix or the urethra. The time interval for transfer of swabs to the diagnostic laboratory is not a significant factor. It is not necessary to use pure cultures on primary isolation plates to obtain definitive results. Nongonorrhoeae neisserias, as well as a large variety of commonly encountered unrelated bacteria, do not react or interfere in the transformation assay when using one of the mutant strains under a standardized set of conditions. The entire assay can be completed in less than 24 h. It has also been shown that type T4 cells of the strain of N. gonorrhoeae employed in the present study are competent for genetic transformation, although type T4 cells are transformed at a significantly lower frequency than are type T2 cells of the same strain.

Amino Acids↗