Three divergent nodA genes in the tropici symbiotic plasmid. A, Maximum likelihood phylogeny of nodA genes. Genes from the tropici pSym are shown in green. Host-legume subfamily affiliation is indicated within brackets (M, Mimosoideae; F, Faboideae). Strain STM3625 possesses two nodA genes. B, Gene neighborhood of the three nodA genes. Genes represented with gray color are hypothetical.