TOXICITY OF 2-MERCAPTOBENZOTHIAZOLE TOWARDS BACTERIAL-GROWTH AND RESPIRATION

Active sludge systems containing benzothiazoles may be intoxicated by 2-mercaptobenzothiazole (MBT). This toxicity towards several bacteria is now confirmed and is situated at around 100 mg MBT l(-1). Octanol-w ater partition coefficients indicated that MBT might interact with mem brane-bound systems. This was confirmed through experiments showing th at bacterial cell respiration was inhibited using lactate or succinate as substrates. Using these substrates and also NADH, it was found tha t their oxidation was also inhibited using isolated membrane fragments of Escherichia coli and Paracoccus denitrificans. Methylene blue redu ction was also found to be inhibited. The oxidation of ascorbate was n ot inhibited in P. denitrificans. From these results it is suggested t hat MBT might interact with the respiratory chain at the level of flav oproteins or quinones and Fe-S clusters.