The averaged median tail moment values for sulfide and butylhydroxyanisoletreated slides were significantly different from sulfidetreated slides.Fpg releases both purine bases with damaged imidazole rings and a deoxyribose derivative, leaving a gap bordered by and phosphoryl groups. This indicates that in addition to inducing DNA strand breaks, sulfide generates significant oxidative damage of DNA.The present data not only confirm these findings but further show that sulfide is directly genotoxic, independent of cellular metabolism, and strongly suggests that this genotoxicity is mediated by free radicals.The present study shows that sulfide induces DNA damage in the absence of cellular metabolism, which indicates that sulfide, or some oxidation byproduct, reacts directly with DNA.In aqueous solution, sulfide spontaneously oxidizes generating oxygen and sulfur center radicals. Compared with the negative control, a significant difference of the average median SCGE tail moment values at all sulfide concentrations was observed. For the data presented, at least eight microgels were analyzed per concentration with nuclei measured per microgel.Similarly, genotoxic concentrations of sulfide are also lower than those reported to be endogenously generated as a signaling molecule by a variety of cell types. Our previous study showed sulfide genotoxicity in whole CHO cells only in the presence of DNA repair inhibitors.These data support the notion that detoxifying and DNA repair enzymes play a vital role in the protection of cells routinely exposed to high concentrations of sulfide.Any compromise in either sulfide detoxification or DNA repair could increase the susceptibility of an individual harboring such alleles to sulfidegenerated DNA damage.Accordingly, it is relatively easy to envision how multifactorial interactions among polymorphic alleles of sulfideresponsive genes and other genes or environmental factors that promote colonization by SRB may contribute to chronic diseases such as colorectal cancer.Butylhydroxyanisole, which acts as a peroxy and alkoxy as well as a hydroxyl radical scavenger, protects the DNA from the radicals formed from sulfide in solution.Reactive oxygen species formation was observed by others after sulfide treatment in cell cultures and tissue explants. To further test the hypothesis that oxidative species are involved in sulfide genotoxicity and to enhance the specificity of resulting DNA damage, we conducted experiments using DNA glycosylase. In an alkaline buffer, strand breaks will be generated due to helimination of abasic DNA lesions, making it detectable by the SCGE assay.The, dihydro oxoguanine is formed when deoxyguanosine reacts with oxidants or ionizing radiation, making it one of the most common oxidative base lesions. A previous study reported that sulfur radicals are responsible for, dihydro oxoguanine formation. The bacterial DNA glycosylase has a eukaryotic functional homologue, the oxoguanine glycosylase. Detailed methods for preparing and electrophoresing the SCGE microgels were published previously. Cellular membranes were removed by an overnight immersion in lysing solution at jC.The microgels were washed once with water and thrice with a neutralization buffer.After the treatment, the microgels were placed in an alkaline buffer in an electrophoresis tank, and the DNA was denatured for min at jC.The microgels were electrophoresed at V, mA, rinsed in cold water, dehydrated in cold methanol, dried at jC, and stored at room temperature in a covered slide box.