Mero-Cy5 reveals relative enzyme activities and drug targets in lysates obtained from normoxic and hypoxic Mtb cultures. Lane 1: no drug pretreatment. Lanes 2–10: drug pretreatment. 2, cephalexin; 3, ceftriaxone; 4, aztreonam; 5, penicillin G; 6, ampicillin; 7, carbenicillin; 8, meropenem; 9, faropenem; 10, clavulanate. Lane 11: lysates not treated with Mero-Cy5. Lane 12: lysates treated with a Cy5-(triazole)-butanoic acid. Putative protein identities were obtained by MS analysis. Legend: Gold stars denote enzymes that retain activity under hypoxic conditions. Red arrows indicate bands with enhanced activity in hypoxia. Black dash-marks indicate bands that were absent in hypoxia but present in normoxia.