Chlorooxirane transformation in cell extract reactions. ○, buffer alone; □, buffer, CoM, and cell extract from strain mc2155(pMV261); Δ, buffer, CoM, and cell extract from strain mc2155(pMV-CoM). Data from two experiments are shown. Chlorooxirane was quantified by the absorbance (550 nm) of its 4-(p-nitrobenzyl)pyridine adduct. Initial concentrations of chlorooxirane in the assays ranged from 0.2 to 0.3 mM.