Mycobacterial and E. coli Culture Conditions

M. smegmatis mc²155 [72] (link), M. tuberculosis H37Rv and Escherichia coli NEB-10β (New England Biolabs UK Ltd) were used in this work. M. smegmatis and M. tuberculosis were grown on Middlebrook 7H11 agar medium (BD Diagnostics) supplemented with 0.5% glycerol and 10% oleic acid albumin-dextrose-catalase (OADC) (BD Diagnostics). When required, filter-sterilised luciferin was added at a final concentration of 0.157 mM. Liquid cultures of M. smegmatis and M. tuberculosis were grown either in Middlebrook 7H9 broth (BD Diagnostics) containing 0.05% Tween 80 (Sigma) and 10% albumin-dextrose-catalase (ADC) enrichment (BD Diagnostics), or (for M. smegmatis Gluc assays) in Luria-Bertani (LB) medium with 0.05% Tween. LB medium was preferred for the Gluc assays because the background of coelenterazine was 100 times lower in that medium than in 7H9 broth. LB medium was used for culturing E. coli. All the strains were grown at 37°C. The following antibiotics were added when appropriate: ampicillin [100 µg ml⁻¹ (Sigma)], hygromycin B [150 µg ml⁻¹ (Invitrogen)] and kanamycin [25 µg ml⁻¹, for mycobacteria, 50 µg ml⁻¹ for E. coli (Sigma)].