['To determine the mechanisms of Bacillus subtilis spore killing by and resistance to an acidic solution containing Fe(3+), EDTA, KI and ethanol termed the KMT reagent.', 'Wild-type B. subtilis spores were not mutagenized by the KMT reagent but the wild-type and recA spores were killed at the same rate. Spores (alpha(-)beta(-)) lacking most DNA-protective alpha/beta-type small, acid-soluble spore proteins were less resistant to the KMT reagent than wild-type spores but were also not mutagenized, and alpha(-)beta(-) and alpha(-)beta(-)recA spores exhibited nearly identical resistance. Spore resistance to the KMT reagent was greatly decreased if spores had defective coats. However, the level of unsaturated fatty acids in the inner membrane did not determine spore sensitivity to the KMT reagent. Survivors in spore populations killed by the KMT reagent were sensitized to killing by wet heat or nitrous acid and to high salt in plating medium. KMT reagent-killed spores had not released their dipicolinic acid (DPA), although these killed spores released their DPA more readily when germinated with dodecylamine than did untreated spores. However, KMT reagent-killed spores did not germinate with nutrients or Ca(2+)-DPA and were recovered only poorly by lysozyme treatment in a hypertonic medium.'] Do mechanisms of Bacillus subtilis spore killing by and resistance to an acidic Fe-EDTA-iodide-ethanol formulation?