In Celebration of Breathing...

There was a big celebration in Cambridge, MA a few weeks ago. It was interesting, in a strange sort of way, to hear a room full of marine bacteriologists singing songs and laughing. Scientists aren’t usually known as party animals, but this WAS the twentieth anniversary of the discovery of a photosynthetic marine microorganism now known as Prochlorococcus."

It all started when Penny Chisholm, a biologist at MIT, went on a cruise. Like the good scientist she is, she took along casual clothing, sun block, and her flow cytometer, a device for detecting microscopic particles, such as cells, in a stream of liquid. In this case, she found previously unknown cells in the sea water.

These tiny cells (about 1500 of them would fit on the edge of a credit card) turned out to be bacteria that have the capacity to perform photosynthesis (basically to split water molecules into H’s and O’s). Moreover, they may be descendants of the very organisms that produced oxygen for sustaining life on a hostile planet a long, long time ago.

In the laboratory we can use a source of direct current (battery) to energize positive and negative electrodes submerged in water. This process, known as electrolysis, will cause the hydrogen and oxygen molecules that make up water to let go of each other and separate. Oxygen will bubble up around the positive electrode and hydrogen around the negative electrode.

This is rather large and cumbersome; however, on its chlorophyll-filled membranes, the tiny Prochlorococcus uses visible light from the sun to do the same thing. The bacterium then releases the oxygen to the atmosphere and combines the left over hydrogen with carbon dioxide from the atmosphere to make high-energy food for marine animals. Pretty neat system, huh?

So once Prochlorococcus appeared on Earth, the atmosphere began filling up with oxygen (well at least to 21%). The destructive ultraviolet rays of the sun began to convert some of the oxygen into ozone to form a layer to protect the Earth from the ultraviolet rays--talk about turning the enemy's strength against them! Without the more powerful uv rays, other life forms could appear and live. The excess oxygen was available for fire, rusting, and breathing!

This bacterium is invisible to the naked eye and yet produces approximately 20% of the oxygen each of us inhales. In addition, it pulls enough carbon dioxide from the atmosphere to provide the basis for the entire marine food web. Small, but plentiful, their numbers extend into the trillion trillions.

Isn't nature wonderful? So there is great cause for celebration. Like most discoveries of this type, it was serendipitous—discovered quite by accident while looking for something else entirely.--mak