1948a Cytochemical mechanisms of penicillin action. VI. The influence of cobalt on the optimal bacteriostatic concentration of penicillin

In penicillin-sensitive organisms the antibiotic blocks the normal functioning of sulfhydryl groups. The blocking results from-SH groups of essential poly-peptides of the glutathione type being dehydrogenated more rapidly than they are rehydrogenated; exposure of the cells to bacteriostatic concentrations of penicillin results in "decompensated respiration, " which is evidenced by a shift of sulfhydryl (-SH) to disulfide (S-S), of aldehydic COH to carboxylic COOH or ketonic CO, or of enolic COH to ketonic CO. Concomitantly with (or because of) these metabolic disturbances in Staphylococcus aureus there occur loss of gram-positiveness, loss of ability to absorb silver and other ions from the sub-strate, loss of capacity to stain with vital dyes such as neutral red, or with basic dyes in general, and loss of ability to retain a number of normal cell constituents such as amino acids, lipids, phospholipids, nucleic acid derivatives, etc. These observations have been reported in a series of publications (Dufrenoy and Pratt, 1947a,b, 1948; Pratt and Dufrenoy, 1947a,b, 1948a,b). Subsequently, Massart, Peters, and Van Houcke (1947) reported that penicillin at concentrations o