( New evidence from open sea experiments ...)MIT: Oceans are a major gene swap-meet for plankton

The research, led by MIT Professor Sally W. Chisholm, is uncovering a challenging new facet of evolution, helping scientists see how photosynthesizing microbes manage to exploit changing conditions such as altered light, temperature and nutrients.

The work will be reported in two articles in the March 24 issue of Science.

As a result of the new findings, "we are beginning to get a picture of gene diversity and gene flow in the most abundant photosynthetic cell on the planet, the Prochlorococcus group of planktonic microbes," said Chisholm, the Lee and Geraldine Martin Professor of Environmental Studies.

These photosynthesizing bacteria "form an important part of the food chain in the oceans, supply some of the oxygen we breathe, and even play a role in modulating climate. So it's very important that we understand what regulates their populations. And now genetic diversity seems to be an important factor," said Chisholm, who holds appointments in the Department of Civil and Environmental Engineering (CEE) and in the Department of Biology.

In one of the journal reports, Chisholm and lead author Maureen l. Coleman, a CEE graduate student, suggest that gene-swapping in ocean microbes resembles the flow of genes already known to occur among disease-causing bacteria. In an ocean context, this exchange mechanism would offer marine microbes a diverse palette of potential gene combinations, each of which might be best suited for a particular environment. This should allow the overall population to persist despite complex and unpredictable environmental changes.

"We postulate that lateral gene transfer ... is an important mechanism for local specialization in the oceans," they wrote in Science. Eventually the scientists hop
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Source:Massachusetts Institute of Technology