Fig. 7.

Complementation studies with EcTS and TbDHFR–TS. (A)–(C) Complementation with E. coli TS and (D)–(F) complementation with T. brucei DHFR–TS.

A. Growth of E. coli thyA^- transformed with pLew82_EcTS or empty vector on thymidine-free medium.

B. Southern analysis of T. brucei DKO transfected with pLew82_EcTS (cDKO_TS). DNA was digested with SacI and SphI and probed with EcTS ORF. The size of the expected fragment is indicated on the right with standard markers on the left.

C. Growth of cDKO_TS in HMI9 medium with or without thymidine. Circles, plus thymidine; squares, no thymidine present. Open symbols depict growth without tetracycline induction and closed symbols with tetracycline. Triangles, growth of DKO in the absence of thymidine. The lines represent the best fits to the equation describing exponential growth as described in Experimental procedures.

D. Growth of E. coli thyA^- transformed with pLew100_TbDHFR–TS or empty vector on thymidine-free medium.

E. Southern analysis of T. brucei DKO transfected with pLew100_TbDHFR–TS (cDKO_DHFR–TS). DNA was digested with HindIII and StuI and probed with TbDHFR–TS. The size of the expected fragment is indicated on the right with standard markers on the left.

F. Growth of cDKO_DHFR–TS in HMI9 medium with and without thymidine (open and closed circles respectively). Open squares, growth of DKO in the absence of thymidine. The lines represent the best fits to the equation describing exponential growth as described in Experimental procedures. Symbols on the x-axis indicate that cell densities are below the limits of detection (i.e. < 10³ ml⁻¹).