Basic Triphenylmethane Dyes and the Inhibition of Glutamine Synthesis by Staphylococcus aureus

SUMMARY: Glutamine synthesis by Staphylococcus aureus is inhibited by the basic triphenylmethane dyes crystal violet, methyl green, fuchsin, pararosaniline, brilliant green and malachite green. In the pH range 6·5–8·5, the inhibitory action of crystal violet is independent of pH, whilst with fuchsin, brilliant green and malachite green, the degree of inhibition is increased by increasing the hydrogenion concentration of the medium. At pH 7·5, inhibitory activity increases in the order: brilliant green, fuchsin, malachite green, methyl green, crystal violet. The effectiveness of a basic triphenylmethane dye as an inhibitor of glutamine synthesis can be correlated with the basic dissociation constant of the dye.