US scientists have found that the gut bacteria Enterococcus faecalis, which is deemed harmless in most people, can produce a DNA-damaging chemical that could increase the risk of colon cancer.
Professor Mark Huycke and colleagues found that certain cellular conditions caused the bacterium to switch from its normal state of respiratory metabolism to another type of metabolism known as fermentative metabolism. A by-product of this fermentative state is the free radical superoxide, which damages DNA. However, the researchers also found that the production of superoxide also led to strong signaling in immune system cells called macrophages, altered cell growth and division of colonic epithelial cells, and altered the activity of 42 genes, some of which possess cancer-promoting properties. All of these changes took place within just six hours.
The findings suggest that the cells of the colon are rapidly and deleteriously affected when E. faecalis switches to fermentative metabolism. They also suggest that the bacterium may play a role in the pathology of colon cancer.
Allen TD, Moore DR, Wang X, Casu V, May R, Lerner MR, Houchen C, Brackett DJ, Huycke MM. Dichotomous metabolism of Enterococcus faecalis induced by haematin starvation modulates colonic gene expression. J Med Microbiol. 2008;57:1193-1204.
