Investigation of malachite green assay for determination of bacterial membrane damage

Determination of the mechanisms of action of antimicrobial substances is an important step in the development of bioactive compounds. Antimicrobial substances may target internal mechanisms of the cell or wall and cell membrane. Bacterial cell membrane may not be a specific target for bacteria because eukaryotic cells contain similar structures. Membrane disturbing agents may damage both prokaryotic and eukaryotic cell membranes. So the determination of membrane damage in the bacteria is very important.Leakage of small molecules from bacterial cell membranes is an important indication of membrane damage and it can be determined by expensive methods including flame photometry, atomic absorption spectrophotometry, ICP and bioluminescense. Spectrophotometric malachite green method has been used in the determination of phosphate in various solutions and it can be a potential alternative to expensive techniques in the determination of bacterial membrane damage. In this study, membrane damages in gram positive (S. aureus) and gram negative (E. coli) bacteria induced by m-cresol and polymyxin B sulphate were comparatively determined using molybdenum blue and malachite green methods. The results of the study show that malachite green method is a sensitive alternative method for the determination of bacterial membrane damage.