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AGE MAKES
THEM FITTER
Have you heard that microbes can adapt to their environment very fast?
Probably yes… and it has been scientifically proved. See below to figure out how!
Back in 1988, evolutionary biologist Richard Lenski,
then assistant at the University of California,
introduced an E. coli strain into a new environment
and observed what happened. However, he wanted
to dig deeper, since he wanted to figure out how
E.coli could evolve over time.
He placed the same strain into 12 different flasks with
the same medium and waited a year and 2,000 E. coli
generations in order to observe how adaptation took
place. This was acknowledged as a “long-term”
experiment and he published preliminary results
with his colleagues.
In the mean time, the rest of the bacteria continued
living in those flasks.
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28850 - Torrejón de Ardoz, Madrid - ESPAÑA
Lenski decided to proceed with the experiment and
pitted bacteria from various evolutionary time points.
Bacteria were frozen in flasks every 500 generations.
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In February 2010, the populations reached the milestone of 50,000
generations. Once Lenski and his team analyzed these flasks, they
reported that the bacteria become more fit over time. The next
500-generation would grow better than the ancestral.
While the bacteria grew, scientists tracked genetic changes with
color-coded genetic markers, in order to be able to distinguish the
generations among flasks.
Lenski described this project as travelling through time, because he and his
team were comparing organisms that lived at different points in the past.
The results came as a surprise to Lenski, who expected fitness to plateau.
However, they began to use new food sources. One of the strains, in 2008,
had evolved to metabolize citrate.
According to John Thompson, an evolutionary biologist at the University
of California, Santa Cruz, the results indicate that there are many adaptive
solutions even in a simple environment, “It is, then, no wonder that life has
evolved to be so diverse."
“The finding contradicts the “naive” view that an organism will cease
getting fitter once it’s well adapted to an environment”, says Rees Kassen,
University research Chair in Experimental Evolution at the University of
Ottawa.” Without Lenski’s experiment, there wouldn’t be much empirical
data to show that. […] The fact of the matter is, it’s the only experiment we
can test,” he says. “No other experiments have gone on as long.”
BIBLIOGRAPHY:
Wiser, M.J., Ribeck N. and Lenski, R.E. 2013.Long-Term Dynamics of Adaptation in Asexual
Populations. Science 342:1364-67, 2013
Blount, Zachary D.; Borland, Christina Z.; Lenski, Richard E. (2008)."Historical contingency and the
evolution of a key innovation in an experimental population of Escherichia coli". Proceedings of the
National Academy of Sciences 105 (23): 7899–906
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C/ La Forja, 9
.
[email protected]
28850 - Torrejón de Ardoz, Madrid - ESPAÑA
Tel. +34 91 761 02 00
Fax +34 91 656 82 28