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Biomedical subjects

E D Gray

Publications and source records attributed to E D Gray.

54 records · Page 3Linked to original sources
PubMed1973

Group A streptococcal bacteriocin. Production, purification, and mode of action.

A bacteriocin, streptocin A, was isolated from the supernatant fluid of tryptic soy broth cultures of Group A streptococcus strain FF-22. Evidence was obtained which supports the view that the failure to recover active streptocin A after growth of the producer strain in certain fluid media is due to the inactivation of the bacteriocin by concomitantly synthesized streptococcal proteinase. The bacteriocin was purified 139-fold and the active product appeared to be of uniform size, having a molecular weight of approximately 8,000. Streptocin A was bactericidal, but not lytic, for a susceptible Group A streptococcus and the lethal effect was markedly temperature dependent. The bacteriocin inhibited the synthesis of DNA, RNA, and protein, and also prevented the uptake and incorporation of glucose by the sensitive cells. Degradation of RNA occurred, but appeared to be less than that produced by a staphylococcal bacteriocin. This effect may be due to differences in the killing potency of the two bacteriocins in preparations having similar inhibitory activity when measured by lawn culture assays.

Alanine↗
PubMed1972

Simple method for the preparation of streptococcal nucleases.

A simple method for preparation and fractionation of the streptococcal nucleases by polyacrylamide gel electrophoresis is presented. The procedure is carried out with ammonium sulfate-precipitated supernatant fluids from cultures of beta-hemolytic streptococci grown to stationary phase. Electrophoresis on polyacrylamide gel and subsequent elution of the fractionated enzymes allows the preparation of sufficient homogeneous nuclease B for a large number of anti-nuclease B titrations.

Ammonium Sulfate↗
PubMed1970

Bactericidal substance from Staphylococcus aureus. Biological properties.

A bactericidal substance previously isolated from phage type 71 Slaphylococcus aureus has been further identified and characterized. Staphylococci belonging to phage type 71 produce the substance in higher titers than staphylococci lysed by other phages in group II in addition to phage 71. Other staphylococci do not produce the bactericidal substance. The bactericidal substance shares several of the properties of bacteriocins but differs from this group of antibiotic substances in some respects. A combination of ammonium sulfate fractionation and gel filtration on a Sephadex G-100 column resulted in considerable degree of purification of the bactericidal substance. The substance is a previously unrecognized product of S. aureus and is distinct from other extracellular products of this organism.

Bacteria↗
PubMed1970

Effect of Bactericidal Substance from Staphylococcus aureus on Group A Streptococci I. Biochemical Alterations.

A bactericidal substance isolated from phage type 71 staphylococci has been studied relative to its mechanism of action on streptococcal cells. The substance exerts its effect best at 37 C. No cell lysis occurs as evidenced by lack of alteration in optical density of susceptible cell suspensions. The bactericidal substance results in immediate cessation of protein and deoxyribonucleic acid synthesis as well as degradation of newly and previously formed ribonucleic acid (RNA). The action on RNA seems to be independent of protein synthesis.

Journal Article↗
PubMed1968

Enzyme and nucleic acid formation during synchronous growth of Rhodopseudomonas spheroides.

The synthesis of various cell components was examined during the anaerobic photosynthetic growth of synchronous populations of Rhodopseudomonas spheroides. Net deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein increased continuously as did the rate of incorporation of radioactive precursors into protein. The rates of incorporation of radioactive precursors into RNA and DNA were marked by abrupt discontinuities. It is not clear whether these discontinuities represent changes in rates of synthesis or fluctuations in precursor pools. Although the synthesis of bacteriochlorophyll occurred in a continuous manner, those enzymes examined which are involved in the synthesis of tetrapyrroles, i.e., succinyl CoA thiokinase, delta-aminolevulinic acid synthetase, and delta-aminolevulinic acid dehydrase, increased discontinuously. Two other enzymes not involved in tetrapyrrole biosynthesis were examined. Alkaline phosphatase increased in a stepwise manner during the division cycle, whereas the synthesis of ornithine transcarbamylase increased rapidly before leveling off for a period of time until synthesis began again. In each instance of discontinuous enzyme synthesis, increases occurred at regular and characteristic times during the division cycle. Ammonium sulfate precipitation was employed to remove low molecular weight end product inhibitors from enzyme preparations. These studies suggested that the stepwise increases in enzyme activity observed in the present investigation were not affected by periodic end product inhibition. A temporal map of enzyme synthesis during the division cycle was constructed. Both delta-aminolevulinic acid synthetase and delta-aminolevulinic acid dehydrase appeared early in the division cycle, whereas alkaline phosphatase and succinyl CoA thiokinase appeared later on.

Alkaline Phosphatase↗