A. tumefaciens

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Classification

Agrobacterium tumefaciens is a pathogenic gram negative bacterium that is usually found in the soil. It is known to be a unique bacterium in which it can transfer genes. A. tumefaciens’s form of movement is lead by the flagellum. The flagellum causes a series of movements like tumbling, running counterclockwise up the gradient and is known to run as a fast as 60 um/s. Agrobacterium tumefaciens are closely related to Rhizobium. The T-DNA induces tumorous and rooty growth that directs the synthesis of opines, carbon, and nitrogen. SIgnificantly, each strain can utilize one of the three opine classes octopine, nopaline, and agropine. The host range of A. tumefaciens range from 331 genera and 643 species.

Genome Structure

The genome structure of Agrobacterium tumefaciens has a very unique genome in which it contains both linear and circular chromosomal structures. This serves for great research advances with its ability to transfer genes into plant hosts and infect acting as a pathogenic agent.

Ecology and Pathogenesis

A.tumefaciens has the capability to act as a pathogenic agent causing disease. A disease caused by Agrobacterium tumefaciens is Crown gall disease. It is known to be saprophytic surviving on decaying organic matter. The pathogenesis of Agrobacterium tumefaciens is characterized to be unique in that A. tumefaciens has the ability to conduct gene transfer. The two steps involved in pathogenesis by A. tumefaciens is 1.delivery of tumorigenic DNA into the plant genome known as transformation, and 2. the resultant alteration of plant cell metabolism. This results in cell poliferation and the synthesis of compounds that are nutritious. During pathogenesis, A. tumefaciens portrays polar attachment to the plant cell. Agrobacterium tumefaciens produces cellulose fibris which serves like an anchor that holds down that bacteria to the plant and traps other bacteria. Multiple levels of disease have been found in the plum, peach, grape, and the aspen rose.

Treatment

To treat Agrobacterium tumefaciens , it is highly suggested to treat prior to infection because if not the development of the disease will progress sometimes independent of the agent. Wounds that may cause infection by bacteria are caused by grafting and transplanting. Applying copper and bleach-based bactericides reduce many A. tumefaciens populations on the surface of plant cells. Another form of treatment is to use avirulent strains of Agrobacterium tumefaciens that act as A. tumefacien antagonists to control Crown gall pathogens. Crown gall disease can be eliminated by using creosote based chemical compounds , copper based solutions, and strong oxidants.

References

McClean, Phillip. "Analyzing Plant Gene Expression with Transgenic Plants." NDSU - North Dakota State University. N.p., n.d. Web. 15 Apr. 2011. <http://www.ndsu.edu/pubweb/~mcclean/plsc731/transgenic/transgenic2.htm>. Winstead, Edward. "The Genome of Agrobacterium tumefaciens." Genome News Network - Home. N.p., n.d. Web. 15 Apr. 2011. <http://www.genomenewsnetwork.org/articles/12_01/A_tumefaciens_genome.shtml>.

Author

Page authored by Shenelle Moolenaar, student of Prof. Doreen Cunningham at Saint Augustine's College.