When reading the last half of Dr.
Sharon Moalem’s book Survival of the Sickest, I was reminded of a recent lecture I had in my Gene, Structure &
Function class. In class, we talked about a special type of virus that infects
E. coli bacteria. This virus is called lambda phage. This virus has been
studied a great deal because it contains clues to understanding the molecular
processes of other viruses and additionally it is relatively easy to work with
in a laboratory because of its small size. Furthermore, this virus is an
important research tool because it has two separate life cycles that it may
choose between. One life cycle, called the lytic lifecycle, results in the
immediate death of the host cell. In the other life cycle, called the lysogenic
lifecycle, the virus integrates into the bacteria’s DNA and lays there dormant
for an indefinite amount of time. The factors that cause lambda phage to choose
one lifecycle over the other are not yet fully understand, but they hold great
implications for discovering what makes other viruses, like say HIV, switch
from being dormant to being deadly.
In order to integrate into a
bacteria cell’s DNA, lambda phage must bind to a specific site on the host
cell’s DNA. In one study, researchers removed this binding site on host cell’s
DNA to see what would happen. Within a very short period of time, the cell
evolved another binding site, allowing the virus to integrate into its DNA. Why
on earth would a cell evolve to help a parasitic virus infect it? My teacher
came to the conclusion that the virus must somehow be beneficial to the
bacteria cell, although it also has the potential to kill the cell at any
moment. This sounds an awful lot to me like the argument that Dr. Moalem was
making in Survival of the Sickest. All
of this is just my long way of saying that I think that Dr. Moalem’s theory
that certain diseases may be beneficial to certain organisms holds water in
molecular cell biology as well as evolutionary human biology.
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