A naturally occurring bacterium that is capable of inserting its DNA (genetic information) into plants, resulting in a type of injury to the plant known as crown gall. In 1980, Marc van Montagu showed that Agrobacterium tumefaciens could alter the DNA of its host plant(s) by inserting its own ("foreign") DNA into the genome of the host plants (thereby opening the way for scientists to insert virtually any foreign genes into plants via use of A. tumefaciens). In 1983, Luis Herrera-Estrella created the first man-made transgenic plant by inserting an antibioticresistant gene into a tobacco plant.

During 2000, Weija Zhou and Richard Vierling proved that A. tumefaciens is at least 10 times more effective (i.e., at "infecting" plants to insert DNA) in space (i.e., weightlessness/ microgravity) than it is when on the surface of the Earth. Among others, Monsanto Company has developed a way to stop A. tumefaciens from causing crown gall, while maintaining its ability to insert DNA into plant cells, and now uses A. tumefaciens as a vehicle to insert desired genes into crop plants (e.g., the gene causing high production of CP4 EPSP synthase, thus conferring resistance to glyphosate-containing herbicide).