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As far as I know, V. cholerae secretes a toxin called choleragen into the intestinal lumen which affects the intestinal epithelial cells causing release of Na+ and Cl- ions into the lumen and reducing the lumen's water potential which causes water to flow into the intestinal lumen resulting in diarrhea. How does this benefit V. cholera in any way?

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After V.cholerae gets into the human intestine it starts to multiply its numbers, and then becomes virulent after sufficiently expanding its numbers. This virulence drives the diarrhea which in part causes the bacteria to slough off into the intestinal lumen, and then into the external environment again.

So in short it uses the human intestine to increase cell numbers.

See work by Bonnie Bassler for a really fascinating understanding of the complexity of this infection.

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  • $\begingroup$ How does the human intestine help V. cholera multiply? I mean, why cannot it multiply in the external environment? $\endgroup$ – Taimur Feb 15 '17 at 20:56
  • $\begingroup$ @Taimur Perhaps it is better to look at this as an empty niche. If the bacteria can expand both in the intestines and in the ocean than it would be advantageous to do both. I don't believe that there is any requirement that that bacteria must infect a host in order to expand. $\endgroup$ – The Nightman Feb 15 '17 at 20:59
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    $\begingroup$ Okay, wait, I actually did some research and found that only humans get cholera. This means that V. cholerae secrete choleragen only to grow and escape human intestines and not of other mammals. Why so? Also, if they can grow in water bodies, why have they developed a specific human-affecting toxin and not a general mammal-affecting toxin? $\endgroup$ – Taimur Feb 15 '17 at 21:16

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