Vibrio cholerae is the bacterium responsible for cholera, one of history's most destructive diseases. Cholera is an infection of the intestinal tract, and rages through the world leaving pain and death in its wake.
About Vibrio Cholerae
A discovery in the mid-19th century fizzles but German physician Robert Koch revives it in 1883 during a cholera outbreak in Egypt. He studies how these bacteria contribute to cholera.
The infection historically causes numerous epidemics. The seventh cholera pandemic (1961-1970) is estimated at a million cases worldwide.
People can have cholera without showing symptoms, or with mild effects. Not all Vibrio cholerae strains are dangerous. Two subgroups in particular, O1 and O139, can be lethal.
Vibrio cholerae is a Gram-negative, facultative anaerobic bacterium. It may be rod or comma shaped. It's highly motile due to a single polar flagellum, which helps it nimbly navigate its aquatic environment .
The bacterium enjoys alkaline conditions. It's oxidase-positive, producing the enzyme cytochrome c oxidase which is needed for cellular respiration.
Vibrio cholerae measures between 1-3 micrometers in length. A micrometer is about 1/1000th or 0.001 of a millimeter. As a facultative anaerobe, V. cholerae can survive with or without oxygen.
This flexibility enables it to inhabit diverse environments, from the salty sea to freshwater lakes. Vibrio cholerae lives in aquatic environments, especially fond of brackish and saltwater.
It can live freely or attach to surfaces of algae, plankton, and shellfish. Stagnant water bodies with poor sanitation are ideal breeding grounds. Human activities like pollution can exacerbate cholera outbreaks.
Vibrio cholerae is heterotrophic, meaning it obtains nourishment from organic matter. In its natural environment, it feeds on dissolved organic carbon and other nutrients in the water.
As it processes food, the bacterium releases organic compounds as waste. If it's one of the pathogens, its potent cholera toxin activates when it infects a human host.
Vibrio cholerae reproduce asexually by binary fission, a rapid process. The bacterium duplicates its genetic material and divides into two identical daughter cells. It can quickly reach infectious levels.
Under optimal conditions, V. cholerae doubles in number every 20 to 30 minutes. A single bacterium potentially gives rise to millions of bacteria in a few hours; but it takes only 10-100 bacteria to cause cholera in a person.
In nature, Vibrio cholerae is a contributing part in the marine ecosystem or river environment. It helps decompose organic matter, recycling essential nutrients. It's also a food source for small organisms.
About Cholera
Cholera is an acute diarrheal illness caused by infection with Vibrio cholerae. Documented outbreaks go back to ancient times.
In the 19th century devastating cholera pandemics rage world-wide. This accompanies the poor sanitation, pollution and overcrowded conditions of industrial revolutions in Europe and the rest of the world.
Symptoms include severe diarrhea and dehydration causing death if untreated. The devastation of the third cholera pandemic (1852-1860) influences public health reform and sanitation globally.
How Vibrio cholerae Cause Cholera
Cholera's devastating effects stem from the bacterium's ability to colonize the small intestine and produce a potent poison, the cholera toxin (CT).
Ingestion: Vibrio cholerae enters the body through the ingestion of contaminated food or water.
Survival in the Stomach: The bacterium must survive the acidic environment of the stomach to reach the small intestine.
Colonization: Once in the small intestine, Vibrio cholerae attaches to the intestinal lining with pili, short hairlike structures.
Cholera Toxin Production: The bacterium produces cholera toxin, which binds to receptors on the intestinal cells.
Disruption of Ion Transport: Cholera toxin disrupts the normal flow of ions and water across the intestinal lining.
Massive Fluid Loss: This disruption leads to a massive outflow of water and electrolytes into the intestinal lumen, resulting in severe watery diarrhea, the defining characteristic of cholera. It's sometimes called "rice-water stool." If left untreated, it causes deadly dehydration within hours. Up to 1 liter of fluid can be lost each hour.
Dehydration and Death: Rapid fluid loss can lead to severe dehydration, electrolyte imbalance, shock and death.
Cholera is largely a human disease but Vibrio cholerae also interacts with marine life. Non-pathogenic strains can be found in crustaceans, mollusks, and fish. Pathogenic strains are specifically adapted to humans.
V. cholerae don't cause illness in the animals but maintain the bacterium's presence. In the environment they're fundamental decomposers dwelling among millions of other microbes. They don't stand out in a crowd.
Facts about Vibrio cholerae and Cholera
Oral rehydration therapy (ORT), a simple solution of water, salt, and sugar, is a highly effective treatment for cholera, replenishing lost fluids and electrolytes.
Cholera is associated with the seasonality of coastal algal blooms off Bangladesh, and with floods.
Some strains of V. cholerae can be regulated by bacteriophages, or viruses able to infect them.
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