“…Fluorescent proteins such as red fluorescent protein (RFP) (Cho et al, 2002) and green fluorescent protein (GFP) (Collins et al, 1998;Changsen et al, 2003) have no exogenous substrate requirement, simplifying quantitation and enabling the easy determination of growth/inhibition kinetics. Luciferase proteins from the firefly (Cooksey et al, 1993;Arain et al, 1996;Shawar et al, 1997) and from Vibrio harveyi (Snewin et al, 1999) utilize luciferin and n-decyl aldehyde substrates, respectively, with the latter yielding a higher signal in mycobacteria. These luminescence measurements, performed in a luminometer, have much higher signal-to-background ratios than is obtained from fluorescence assays thereby making them potentially useful for also measuring inhibitor activity in Mycobacterium tuberculosis-infected macrophages (Arain et al, 1996) and in mice (Snewin et al, 1999).…”