Rhizobitoxine producers gain more poly-3-hydroxybutyrate in symbiosis than do competing rhizobia, but reduce plant growth.

Legume sanctions against rhizobia that fix less nitrogen should exert a strong selection for more beneficial genotypes of rhizobia, but strains providing little host benefit are common. One reason may be that some rhizobia chemically manipulate the host, undermining the efficacy of sanctions. Here we show that the ethylene inhibitor, rhizobitoxine (Rtx), is an example of such a manipulation. Rtx-producing rhizobia decreased legume growth, but benefited relative to an isogenic, non-producing strain on the same plant by accumulating 47% more of the storage lipid poly-3-hydroxybutyrate (PHB).