Fig. 2.

Split-Trp growth assay in M. smegmatis. Recombinant M. smegmatis ΔhisA-expressing pairs of proteins fused to Ntrp and Ctrp were diluted 1- or 10-fold in water and spotted in parallel onto minimal medium and medium plus Trp. The pair of Ntrp-Esat6 and Cfp10-Ctrp was used as a positive control (the early secreted T cell antigens Esat6 and Cfp10 from Mtb form a tight, 1:1 complex). Negative controls and extra positive controls were performed (see SI Materials and Methods). Images were taken after a 3-week incubation.