Pyrithione biocide interactions with bacterial phospholipid head groups.

Sodium pyrithione and zinc pyrithione (NaPT and ZnPT, respectively) are antimicrobial agents widely used in both the cosmetics and fuel industries. They are also utilized in the mining industry because of their metal chelating properties. They have been shown to depolarize membrane electropotential in fungi and are also known to inhibit fungal and bacterial substrate transport processes. Recent work has shown that both pyrithiones cause the leakage of intracellular material (potassium ions and O.D.260 nm absorbing material) from exposed bacterial cells. The work here reports studies on the interactions between the pyrithiones and the bacterial phospholipid head group structures, at both a practical and a theoretical level, utilizing tube dilution neutralizer studies, scanning spectrophotometry and molecular modelling. The tube dilution neutralizer studies exhibited a decrease in minimum inhibitory concentration (MIC) for both pyrithiones in the presence of extracellular phosphatidyl-ethanolamine and EDTA. Scanning spectrophotometry exhibited the chelation of the central zinc atom from the ZnPT chelate by the addition of EDTA. Molecular modelling studies exhibited the chelation of the phosphatidyl-ethanolamine head group by ZnPT. Zinc pyrithione also exhibited an interaction with the ammonium tail of the head group structures. Sodium pyrithione exhibited electrostatic interactions with the phospholipid head groups in the molecular modelling studies.