symbiotic islanda very large gene cluster (‘island’), typically found on the CHROMOSOME of RHIZOBACTERIA such as Mesorhizobium loti, necessary for establishing SYMBIOSIS with leguminous plants (see LEGUME). The genes include those for NITROGEN FIXATION and root nodulation. In M. loti the island has significantly different CODON USAGE to that of the rest of the chromosome suggesting that it may be of foreign origin.Analogous to PATHOGENICITY ISLAND.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005