Relation between iron uptake, pH of growth medium, and penicillinase formation in Staphylococcus aureus

The uptake of iron and the formation of penicillinase was examined in cultures of wild-type Staphylococcus aureus. Uptake of iron was about twice as great at pH 4.7 as at pH 7.4 At pH 4.7, increase in iron uptake in the range of 1.0 to 4.0 mug per mg of bacterial protein was associated with a progressive increase in the rate of penicillinase formation, but a direct correlation between cellular iron content and rate of enzyme formation was not demonstrated. Addition of iron to deferrated medium enhanced penicillinase formation at pH 6.5 to 7.4 two- to fourfold in cultures induced with benzylpenicillin and in uninduced cultures. To demonstrate an effect on the uninduced cells, it was necessary to increase iron uptake by preliminary incubation of cells with iron in buffer. Calcium and certain other ions depressed iron uptake at acidic and at neutral pH, and, presumably as a result of this action, depressed the formation of penicillinase. Iron did not enhance penicillinase formation at pH 4.7 by two penicillinase constitutive mutants nor by wild-type cells undergoing induction at pH 6.5 by cephalosporin C or methicillin. After removal of cephalosporin C or methicillin during an early phase of induction, residual synthesis of enzyme was increased by prior uptake of iron. The results are considered compatible with the concept that uptake of iron, especially at acidic pH, interferes with the formation or function of penicillinase repressor.

Recombination of heavy and light chains from human immunoglobulins

The recombination of reduced, alkylated heavy and light chains from three IgG, two IgM and one IgA pathological protein and from normal IgG has been quantitatively studied.

All γ, α and μ chains showed some recombination with all κ and λ chains tested. One of the IgG and two of the IgM proteins showed more than 50 per cent recombination and in these there was evidence of a selective reconstitution of autologous chain pairs; the structural features which determine re-association appear to be independent of the electrophoretic mobility, or antigenic and allotypic specificity of the interacting chains. The chains of normal IgG and of three myeloma proteins showed a low percentage recombination and these autologous chain pairs did not combine preferentially. It appears that immunoglobulin chains show a variable ability to regain their native configuration after isolation.

Two pathological κ chains which were identical in electrophoretic mobility and Inv specificity but not equivalent in re-association behaviour showed well marked differences in tryptic peptide patterns. This indicates that the number of chemically distinct human light chains exceeds the forty variants previously postulated on the basis of antigenic, allotypic and electrophoretic differences.

Histochemical demonstration of pentose shunt activity in smears from the uterine cervix

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