SUMMARY: Researchers looked at 122 samples of cholera in 8 different cholera patients; five were from Bangladesh and three were from Haiti. They found that the cholera bacteria genomes were different in water versus the human gut; one particularly interesting mutation was that the bacteria stopped forming biofilm in humans. Biofilm helps cholera bacteria survive in aquatic environments, but not in the host. Another mutation that was found that could help the bacteria survive in humans was an antibiotic resistance gene. There were also genetic differences in the cholera between the people in Bangladesh versus Haiti (cholera has been in Bangladesh for hundreds of years, but it has only been in Haiti since 2010).
LESSON COMMENTS: Horizontal gene transfer, DNA mutations, and evolution are good topics that this paper can help illustrate. The discussion section talks about the bottlenecking of bacteria once they are living in the human gut. Why would bacteria need more biodiversity in an aquatic environment and less in the human gut?
Levade I, Terrat Y, Leducq J, Weil A, Mayo-Smith L, Chowdhury F, Khan A, Boncy J, Buteau J, Ivers L, Ryan E, Charles R, Calderwood S, Qadri F, Harris J, LaRocque R, Shapiro B. 07/12/2017. M Gen 3(12): doi:10.1099/mgen.0.000142