Bacteria are able to cause tumors in plants because they can modify the genomes of plants. Such alteration is done by skillfully using the first line of defense of plants. With the use of the proteins found in plants, the genes of such bacteria break into the plant nucleus. Then, such bacteria gain access to the plant genome. There, they reprogram the metabolism of plants to suit their needs.

While the genetic manipulation of plants may be a subject of great controversy in Europe, certain bacteria already practice such tactic naturally. The crown-gall bacterium (Agrobacterium), commonly known as soil bacterium, takes control of the genetic make-up of plants through the insertion of its own DNA into the plant nuclei and, as a natural progression, into the genetic material of the plant cells.

With such infiltration, the genetically modified plants are reprogrammed in order to cause the division of the uninhibited cell and the production of nutrients to feed the bacteria. However, what was not previously understood is exactly how bacteria genes gain access to the nucleus of the plant cell, considering that the defense mechanisms of plant cells react so fast to the invasion of bacteria.

A startling detail of this process has been discovered by the team, led by Professor Heribert Hirt, of the Max F. Perutz Laboratories at the University of Vienna and, later, of the URGV Plant Genomics Institute near Paris. VIP1, which is a protein found in plant cells, become the center of their research. It was previously known that this protein assists the transport of the bacterial DNA, T-DNA, into the plant nucleus. However, the exact role of the said protein was unclear then. The group of Hirt was able to find out that the T-DNA bacteria use the VIP1 to transport themselves to the nucleus because the said protein is responsible for the regulation of various genes, which are designed to become defenses against bacterial attacks.

Hirt further explained that plants have an immune defense mechanism that takes action when certain molecules of the invader have been detected. As such, genes in the nucleus and specific protein kinases in the cytoplasm are activated. These enzymes control the activity of other proteins through addition phosphates. One of these phosphorylated is VIP1, which is able to infiltrate the nucleus only after this phosphorylation. As such, relevant defense genes are activated.

In studying bacteria in plants, ab easy piece of equipment that can aid a researcher is the brightfield light microscope. A brightfield light microscope illuminates, not only the bacterial specimen sample, but also the microscopic plant material through transmitted white light, which is the illumination that stems from below and observed from above. Aside from the built-in illuminator, a good brightfield light microscope is prepared with an adjustable condenser that is equipped with an aperture diaphragm or contrast control. Aside from those, other parts of the brightfield light microscope are the mechanical stage and the binocular eyepiece tube. Among the significant rewards of using a brightfield light microscope are the effortlessness of the technique employed and the minimal sample preparation.