FIG 2.

EPR spectra of DMPO adducts obtained in RIF-treated and -untreated M. tuberculosis suggest ·OH involvement. DMPO (0.1 M) was added to lysates of M. tuberculosis H37Rv grown for 3 days in the absence of RIF (spectrum A) or in the presence of 8 μg/ml RIF (spectrum B). Lysates from samples grown in the presence of RIF were treated with 10 μg/ml SOD (spectrum C), 10 μg/ml CAT (spectrum D), 100 mM THIO (spectrum E), 10 μg/ml SOD and 1 mM DTPA (spectrum F), or 1% ethanol (spectrum G) or treated in hypoxic conditions by 15 min N₂ bubbling (spectrum H). No signals were detected in PBS in the absence of M. tuberculosis lysates (spectrum I). Adduct attribution: DMPO-OH (a^H = a^N = 14.9 G; marked with ○), DMPO oxidation product (a^N = 15.4 G and a_β^H = 23 G; marked with ●), and DMPO-CHCH₃OH (a^N = 15.4 G and a_β^H = 22.7 G; marked with ▼). M. tuberculosis lysates were incubated with scavengers at 37°C, 10 min before DMPO addition. Spectra were acquired at 37°C, 2 min after DMPO addition. For instrument settings, see Materials and Methods. The EPR spectra obtained after 1 day of incubation with RIF were superimposable to those obtained after 3 days shown here. Mtb, M. tuberculosis.