These bubble-headed creatures are known to scientists as bacteriophages,
viruses that target bacteria. The head serves as a reservoir for DNA and
the tail serves the same function as that long pointy thing you get jabbed
with when you go to the clinic for a booster shot. Attaching to a specific
site on the bacterial cell wall, the virus squirts DNA -- the same kind of
hereditary material that can be found in human and other animal cells --
through the tail into the host bacterium. Ouch! Bacteriophages are useful
to scientists because they can be used to model other types of viruses,
including the viruses that can make people sick. They are among the
smallest of organisms. You could fit about 680,000 of these creatures on
the head of a pin. If you like this Cool Science Image, you can see more
electron micrographs in a library of such images at the University of
Wisconsin-Madison's Institute for Molecular Virology.
Photo courtesy of Maria Schnos with special thanks to Ross Inman.
