Are viruses alive? Viruses have found an ingenious way of
perpetuating themselves, without ever being truly alive.
Unlike most living organisms, they can be frozen or boiled,
but then explode into life if conditions are right. Viruses
enter other organisms' cells and take over their
machinery, making copies of themselves, but they can't "reproduce" on
Using a combination of imaging techniques, researchers
have determined that some viruses infect cells by piercing
the cells' outer membranes, digesting the walls and
injecting virus DNA into the cell. These findings explain
how viruses invade cells and offer a new way to deliver
genes and drugs directly into cells.
The study, funded by the National Science Foundation's (NSF) Biological Sciences Directorate,
was led by researchers Michael Rossman of Purdue University
and Vadim Mesyanzhinov of the Shemyakin-Ovchinnikov Institute
of Bioorganic Chemistry in Moscow. The team studied the structure
of the bacteriophage T4—a virus that attacks the familiar
microbe E. coli.
Some strains of E. coli live in the human gut
where they supply us with essential vitamins. Other strains
are famous for causing food poisoning. It’s possible,
say scientists, that studies of viruses can help biologists
develop strategies to fight deadly bacterial infections.
Efforts to use viruses to target antibiotic-resistant bacteria
are already underway.
The researchers combined x-ray crystallography, which provides
a 3-D picture of the viruses’ proteins, with cryo-electron
microscopy images to determine how T4 proteins rearrange
themselves during cell infection.
Now that scientists have found out what the relationships
are among the T4 component proteins, they’re analyzing
other processes that occur during an infection. They’re
also studying other viruses to identify the common or distinguishing
features of each virus type.
These studies provide hope that engineered viruses might be
used to seek out and destroy specific cells or deliver a "payload" that
might include new genes or drugs.
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