Mysterious microbes trade genes
Bacteria with a jaw-breaking name are forcing scientists to rethink the biology of microscopic ocean life. These microbes eluded the explorations of marine biologists for centuries. Now a growing understanding of their ability to adapt to changing environments is rewriting the rules of how marine microbes interact and evolve.
Sally Chisholm at the Massachusetts Institute of Technology and Rob Olson at the Woods Hole (Mass.) Oceanographic Institution discovered this minute wonder - called Prochlorococcus - in 1985. Since then, Chisholm's lab has taken the lead in exploring the microbe's lifestyles and genome. Lab members' latest findings show that different strains of the bacterium swap genes as readily as college students swap songs over the Internet. Viruses play the role of computer file-swapping programs.
In her lab's announcement, Professor Chisholm explains that the new findings are beginning to paint "a picture of gene diversity and gene flow in the most abundant photosynthetic cell on the planet." Papers published last month in Science magazine present the technical details. From being totally unknown to science, this photosynthetic marvel has revealed itself to be so abundant that it accounts for up to 48 percent of the ocean's net primary biological production. Chisholm says it forms "an important part of the food chain in the oceans." It even supplies "some of the oxygen we breathe."
The studies show that the genomes in all the strains of the bacterium have distinctive regions in their DNA - so-called genetic "islands" - that have a variety of potentially useful instructions. They represent contingency plans for meeting the challenges of marine life.