Figure 3. The StLT2 rhs locus encodes cognate toxin/immunity pairs.

A) Expression of rhs-CT^main or rhs-CT^orphan inhibits the growth of StLT2 cells. Expression the plasmid-borne rhs-CT genes was induced by addition of L-arabinose at the indicated time, and cell growth was monitored by measuring the optical density at 600 nm (OD₆₀₀). The cells also co-expressed either rhsI^main (dark squares) or rhsI^orphan immunity genes (light grey diamonds) from IPTG-inducible promoters. Growth is compared to control cells that carry the empty vector plasmids (triangles). B) Expression of rhs-CT^main or rhs-CT^orphan inhibits the growth of E.coli cells. The rhs-CT and rhsI genes were expressed in E. coli cells from the same plasmids described in panel A, and growth monitored by measuring the OD₆₀₀ of the cultures.