Final answer:
Agrobacterium tumefaciens is unique for its ability to naturally alter the genome of its plant hosts through transformation, making it an important tool in the genetic engineering of transgenic plants.
Step-by-step explanation:
Agrobacterium is the only known natural example of an organism that alters the genes present in its host cells via a process known as transformation. This type of horizontal gene transfer is facilitated by Agrobacterium tumefaciens, which transfers DNA to a plant host, causing tumor formation. Transformation of plants is a significant application of this process, as A. tumefaciens has a broad range of hosts and has been used to introduce desired DNA fragments into plants, creating transgenic organisms.
In the natural world, A. tumefaciens harbors Ti plasmids (tumor-inducing plasmids) that integrate their DNA into an infected plant's genome, causing tumors. However, this natural transfer capability has been harnessed in genetic engineering to remove tumor-causing genes and insert genes of interest to produce transgenic plants. These altered plants can express new traits, such as resistance to diseases or harsh environmental conditions.