The Inhibition of Bacterial Growth by Colloidal Heavy-metal Sulphides and by Colloidal Sulphur

Abstract

SUMMARY: Colloidal copper sulphide is inhibitory to staphylococci and a number of other Gram-positive organisms, but has little effect on Gram-negative organisms. Its formation when cystine and peptides containing cystine are autoclaved with copper is thought to be responsible for the anti-staphylococcal activity of heat-sterilized copper-containing peptone solutions. Colloidal sulphur is active against the cocci but the inhibition differs in some respects from that of copper sulphide, notably in the ease with which it can be reversed by cystine, cysteine and mercapto-acetic (thioglycollic) acid. Iron and manganese sulphides also inhibit bacterial growth and the possible significance of this inhibition on the production of anaerobic toxins is discussed.