🦠 Cholera (WJEC)

Cholera is an infectious disease caused by Vibrio cholerae, which is a major cause of death in areas of the world where a proper infrastructure for good sanitation doesn’t exist. Bacteria are ingested by consuming contaminated water and food. The water becomes contaminated when a person with the disease (which causes severe diarrhoea) produces the faeces which then carry the bacteria in the water supply.


As all bacteria, Vibrio cholarae is a prokaryotic organism. Prokaryotes do not have a nucleus like eukaryotes do. Their DNA is not membrane-bound, just free in the cytoplasm.



The cholera bacteria cause severe diarrhoea by producing a toxin which binds to receptors in the small intestine; this in turn activates cyclic AMP (which is a messenger molecule) which results in chloride pumps staying open all the time. Under normal conditions, these pumps would open and close accordingly to adjust water content in the small intestine. In cholera however, chloride ions are free to rush out into the lumen (β€œempty” space), as well as other ions such as sodium. This causes the water potential in the lumen to decrease (so water moves in by osmosis from cells lining the small intestine into the lumen), which results in a high amount of water being lost from the…