The Composite Genome of the Legume Symbiont Sinorhizobium meliloti
Francis Galibert, Turlough M. Finan, Sharon R. Long, Alfred Pühler, Pia Abola, Frédéric Ampe, Frédérique Barloy-Hubler, Melanie J. Barnett, Anke Becker, Pierre Boistard, Gordana Bothe, Marc Boutry, Leah Bowser, Jens Buhrmester, Edouard Cadieu, Delphine Capela, Patrick Chain, Alison Cowie, Ronald W. Davis, Stéphane Dréano, Nancy A. Federspiel, Robert F. Fisher, Stéphanie Gloux, Thérèse Godrie, André Goffeau, Brian Golding, Jérôme Gouzy, Mani Gurjal, Ismael Hernandez-Lucas, Andrea Hong, Lucas Huizar, Richard W. Hyman, Ted Jones, Daniel Kahn, Michael L. Kahn, Sue Kalman, David H. Keating, Ernö Kiss, Caridad Komp, Valérie Lelaure, David Masuy, Curtis Palm, Melicent C. Peck, Thomas M Pohl, Daniel Portetelle, Bénédicte Purnelle, Uwe Ramsperger, Raymond Surzycki, Patricia Thébault, Micheline Vandenbol, Frank-J. Vorhölter, Stefan Weidner, Derek H. Wells, Kim Wong, Kuo-Chen Yeh, Jacques Batut- Multidisciplinary
The scarcity of usable nitrogen frequently limits plant growth. A tight metabolic association with rhizobial bacteria allows legumes to obtain nitrogen compounds by bacterial reduction of dinitrogen (N 2 ) to ammonium (NH 4 + ). We present here the annotated DNA sequence of the α-proteobacterium Sinorhizobium meliloti , the symbiont of alfalfa. The tripartite 6.7-megabase (Mb) genome comprises a 3.65-Mb chromosome, and 1.35-Mb pSymA and 1.68-Mb pSymB megaplasmids. Genome sequence analysis indicates that all three elements contribute, in varying degrees, to symbiosis and reveals how this genome may have emerged during evolution. The genome sequence will be useful in understanding the dynamics of interkingdom associations and of life in soil environments.