Lee Dye
Published September 26, 2012 by ABCNews
Summary
In 1988, Richard Lenski, a professor of microbiology and
molecular genetics at Michigan State, began an experiment to study evolution. Because
studying evolution requires many generations, scientists have to use organisms
that reproduce quickly. So, for the past 25 years, Lenski and his team have
been studying the bacteria E. coli. They have 12 populations of E. coli that
create about 7 generations in 24 hours, and now have over 56,000 generations of
E. coli. They take samples periodically and freeze them, providing a record of
all the evolutionary changes from the beginning of the experiment.
E. coli has a special trait: they cannot eat citrate in
the presence of oxygen. However, at about generation 33,000, the scientists
noticed a large change. In one of the 12 populations, the E. coli began to eat
the citrate and that population grew rapidly with the addition of the new
nutrient. The scientists studied the frozen records in order to find the cause
of the change by sequencing the genomes. They discovered that there were three
mutations that occurred before the E. coli could finally eat the citrate. The first
took place at about generation 31,000, but it still took two more mutations
before the bacteria began to really consume the new nutrient. The E. coli had
evolved to consume a food source that gave them an advantage over the other
populations, as shown by their rapid growth. Previously, E. coli did not eat citrate. This change showed that complex traits can evolve quickly, and
that species are always changing.
Connection
This article connects to our units on evolution, genetics, and heredity.
The E. coli experiment showed how the bacteria evolved. They began to eat
citrate, which is a trait different from other E. coli. Natural selection would
have selected for the individuals with the mutation; they were more suited to
the environment because they could take in more nutrients. Also, it
connects to genetics because the change was caused by a beneficial mutation to
the bacteria’s DNA. Lastly, it relates to heredity because the new trait was
passed down to the offspring.
What nutritional value does the citrate provide for the E. Coli that helps them grow rapidly?
ReplyDeleteWhat nutritional value does the citrate provide for the E. Coli that helps them grow rapidly?
ReplyDeleteWhich generations did the next two mutations occur?
ReplyDeleteIf the species, E. coli, keep undergoing changes, Is there possibilities that it will evolve into a harm bacteria to humans in the future
ReplyDelete