Fig. 2.

Expression levels of cosmid encoded lacZ genes introduced by transduction or resident in the host strain. In panel A strain MC1061 carrying plasmid pCY913 was transduced with particles carrying cosmid pCY915B at either 5 or 10 ctu/cell (left two sets of columns) and compared with the same strain carrying both the pET-lacZ plasmid and resident pCY915B (which have compatible origins and selectable markers). A strain carrying pET-lacZ and the empty vector from which pTara was derived was also tested. Expression was assayed 3.5 h after induction. Ara denotes the presence or absence of 0.2% arabinose. In panel B lacZ cosmid pCY914 was either transduced (5 ctu/cell) into the ΔlacZY host strain Tuner (which encodes T7 RNA polymerase on the chromosome under control of LacI) as described in Table 3 or was resident in Tuner. β-Galactosidase expression in the presence or absence of 1 mM IPTG was assayed 3.5 h after induction.