Cancer-Causing Bacteria Induces Apoptosis

Barry Marshall discovered that stomach ulcers are caused by bacteria after he drank a petri-dish containing Helicobacter pylori, a bacteria. He subsequently developed gastritis as a result, then cleared this through the use of antibiotics. The discovery that stomach ulcers could be treated with antibiotics was significant for the medical community as they could lead to stomach cancer and duodenal ulcers.

Helicobacter pylori Micrograph

Researchers have recently identified a bacterial toxin, called vacuolating cytotoxin A or VacA, that plays a role in apoptosis. Apoptosis is a process of programmed cell death. VacA had previously been shown to cause cell death, which is important to the development of gastric cancers. Instead of attacking the cells lining the stomach, Helicobacter pylori causes the cells to undergo apoptosis. Too little or too much apoptosis can lead to several conditions, such as neurodegenerative diseases, cancers, and autoimmune disorders. Apoptosis can occur naturally for several reasons such as well cell population needs to be regulated or as a defense mechanism. Cell death can also be induced due to damage in the cell caused by disease or noxious substances.


VacA is a product of Helicobacter pylori. In order apoptosis to occur, the mitochondria are targeted by VacA, since these parts of the cell are responsible for energy production. VacA makes the outer membrane of the mitochondria permeable,disrupting its electron gradient. This electron gradient is needed for oxidative phosphorylation during cellular respiration. Thus, the mitochondria is unable to produce adequate amounts of usable energy for the cell. In addition, VacA disrupts the structure of mitochondria by preventing them from forming a network and effectively isolating them. Since having functioning mitochondria is essential to cell life, the VacA results in the cell killing itself through apoptosis. Through these mechanisms, Helicobacter pylori causes cell death of stomach cells in small areas, which can then results in gastric cancer and, in less severe cases, peptic ulcers.


Click here to access the article on the cancer-causing bacteria and here to access the article that I got my general information on apoptosis from.