Fighting for survival in the gut: Unravelling the hidden variation in bacteria

Link
http://www.sciencedaily.com/releases/2014/03/140306191438.htm
This article was written by the Instituto Gulbekian de Ciencia and published on March 6, 2014.

Summary
Three research groups from the Instituto Gulbenkian de Ciencia collaborated to find out for the first time how E. coli adapts and evolves in the mouse intestine. The researchers fed the mice E. coli. and observed a large genetic variation over time. By analyzing the mice's feces, the data indicated that many E. coli with different advantageous mutations rapidly emerged and were competing for fixation in the gut. The researchers genetically tested the E. coli strains to identify the genes responsible for the bacteria's adaptations. The results show that certain genes were shut off to allow E. coli to grow better in the presence of molecules produced by the mouse intestine. There were also changes in the genes regulating anaerobic respiration. More importantly, the researchers discovered that the same mutations appeared in various E. coli populations evolving in different mice. This evolution of E. coli through natural selection also happens in human intestines. Isabel Gordo, the leader of the study says that their investigation will make way for interesting research studies in the future about evolution in healthy and nonhealthy hosts. The researchers were surprised at the speed at which evolution took place in the gut and how consistent the evolutionary pattern was for E. coli. They say it's necessary for scientists to move away from studies on the Petri dish and experiment on vertebrates, which could help find new ways of fighting diseases.

Relevance
This article relates to what we learned in the pre-lab of the term lab report- bacteria become antibiotic resistant through natural selection. From our textbook, we read that a population of bacteria could have genetic variation through transformation, conjugation, or transduction. Due to genetic variation in a bacterial colony, some may carry a mutation that causes them to be resistant to a certain antibiotic. Overtime, each new generation of bacteria has a higher proportion of individuals with the resistant trait. In the same manner, a population of bacteria such as E. coli evolves in the mouse intestine by the same process. There was a large genetic diversity of E. coli with different advantageous mutations. The difference was that the environment wasn't necessarily selecting for mutations causing the bacteria to be antibiotic resistant. Additionally, the article says that the evolution of E. coli happens in human intestines. In the Microbe Zoo activity, we know that E. coli does live in human intestines and provides vitamin K and some vitamin B for us.