Question

Question 10 (5 pts.):​ Why do you think cholera would choose to colonize the intestines of its host, as opposed to other parts of the body? (Try to think about what the bacteria might gain from living in the intestines.)

Question 11 (5 pts.):​ Why do you think it is important for ​V. cholerae​ to attach themselves firmly to the epithelial cells of the intestines, as shown in the picture above?

Question 12 (5 pts.):​ Suggest a reason why ​V. cholerae​ would benefit by causing their hosts to have excessive, watery diarrhea? How could this help the bacteria in their cycle of infection?

Answer 1

10. A bacterium called Vibrio cholerae causes cholera infection. The deadly effects of the disease are the result of a toxin the bacteria produces in the small intestine. The toxin causes the body to secrete enormous amounts of water, leading to diarrhoea and a rapid loss of fluids and salts (electrolytes). These bacteria multiply rapidly in the small intestine and quickly colonize over there.

11. To cause the diarrheal disease cholera, Vibrio cholera must effectively colonize the small intestine. In order to do so, the bacterium needs to successfully travel through the stomach and withstand the presence of agents such as bile and antimicrobial peptides in the intestinal lumen and mucus. It attaches itself firmly to the receptors present in epithelial cells of the intestines so that it may not get washed away by the intestinal contents or juice.

12. Microbiologists have studied the genetic mechanisms by which the V. cholerae bacteria turn off the production of some proteins and turn on the production of other proteins as they respond to the series of chemical environments they encounter, passing through the stomach, through the mucous layer of the small intestine, and on to the intestinal wall. Of particular interest have been the genetic mechanisms by which cholera bacteria turn on the protein production of the toxins that interact with host cell mechanisms to pump chloride ions into the small intestine, creating an ionic pressure which prevents sodium ions from entering the cell. This ultimately causes diarrhoea.

Bacteria probably are capable of surviving in this environment which is created after producing toxins and thus are able to complete their life cycle in the host.