Agrobacterium

INTRODUCTION

Agrobacterium Tumefaciens is an aerobic gram negative bacteria that is commonly known as a causal agent of Crown Gall disease in a wide array of plants. Agrobacterium Tumefaciens uses horizontal gene transfer “which is any process in which an organism transfers genetic material to another cell that is not its offspring.” (Black, Microbiology, pg13) to cause tumors in plants. It causes tumors by transferring a small segment of its DNA and inserting itself in a semi random location in the plants genome.

We investigated the effect Agrobacterium Tumefaciens had on the Kalanchoe plant and how it supported Koch’s Postulates. Koch’s Postulates was designed to determine the causal agents of plant disease and to associate a particular organism with a specific disease. Koch’s Postulates are as follow: (Black, Microbiology, pg13)

1. The specific causative agent must be found in every case of the disease.

2. The disease organism must be isolated in pure culture.

3. Inoculation of a sample of the culture into a healthy susceptible animal or plant must produce the same disease

4. The disease organism must be recovered form the inoculated animal or plant

METHODS

After obtaining our Kalanchoe plant, we accurately cut a six millimeter triangular cut in two leafs. Once we had cut the leafs we sterilized the inoculation loop by placing it on the Bunsen burner until the sterile loop had turned red, we then waited a few minutes for the sterile loop to cool. After the sterile loop had cooled we inoculated one leaf with the bacteria Argobacterium Tumefaciens. We than placed a piece of tape around the triangular cut in the leaf, before e we had placed the tape around the cut we labeled on the tape Agrobacterium Tumefaciens so we knew which leaf had been inoculated. Next we labeled control on another piece of tape and placed that around the second leaf. We than incubated the plant for four weeks. After four weeks had gone by we obtained our plant and checked to see if any tumors had occurred on the leaf and stem.

RESULTS

Only one visible tumor could be seen on the Kalanchoe plant, the small white tumor had grown above the cut in the leaf inoculated