understanding the mode of action of industrial biocides is is important in optimizing their use and combating resistance if encountered[3]. The antimicrobial effects of isothiazolone biocides have been broadly defined for CMIT and BIT [1,3-11]. These biocides function as electrophilic agents, reacting with critical enzymes to inhibit growth and metabolism, with cell death occurring after several hours contact. Less is known about the mechanism of MIT and DCOIT. Oxidizers also function as electrophiles, with rapid speed of killing, whereas quats and other membrane active agents tend to directly affect cell membranes (Figure 1) [3].