Mortality in S. littoralis. Shown is the mortality in S. littoralis infected with the TT01α P. luminescens wild-type form (○), the VAR* phenotypic variant (▪), and VAR* overexpressing toxins or potential toxin genes: the pirAB locus (✳), the pit gene (⧫), and the xnp2 gene (▴). Bacteria obtained at the end of the exponential growth phase were injected into fourth-instar larvae. Mortality values are based on data obtained after the injection of 20 larvae. Note that the virulence of the VAR* variant harboring the pBB-xnp2 plasmid is more attenuated than the VAR* virulence; this is probably due to the energy cost necessary to replicate a plasmid with a large insert (7.3 kb) compared to the 0.5- and 1.7-kb inserts of the pBB-pit and pBB-pirAB plasmids, respectively.