Wednesday, May 07, 2008

The dance of life

Anne sent me this pic the other day, bacteriophages attacking a bacterium. It was recently featured as an APOD (astronomy picture of the day) on the APOD site. Not quite sure what bateriophages have to do with astronomy, although they do look a bit like lunar landers setting down on a tiny moon.

They are viruses, of course. Like other viruses, they lack the resources to make their own energy or proteins. They can only reproduce and build their shells by hijacking the chemical apparatus of an invaded cell. Phage viruses are parasitical on bacteria. They sit on the surface and inject their genetic material (RNA or DNA) into the bacterium, commandeering the host's reproductive machinery to make more phages, in the process often killing the host.

Where did they come from? Some scientists believe viruses are degenerate life-forms that have lost every animating function except the minimum genes essential to their parasitic way of life. Other scientists suspect viruses evolved inside cells, as organelles, and subsequently escaped to take up their vagabond existence. Then again, maybe they evolved on a parallel track to cellular life.

This electron micrograph of bacteriophages reminded Anne of angels dancing on the head of a pin. And when you think about it, they are no less improbable than a company of angels. They may even turn out to be angelic allies in out fight against bacterial human pathogens. In the meantime, there they dance, little APOD pods on their spidery legs, and millions could gaily cavort on the head of a pin. Holy and terrible. Beautiful and scary.