In one report, Chisholm and scientist Maureen Coleman suggest that gene-swapping in ocean microbes resembles the flow of genes already known to occur among disease-causing bacteria. In an ocean habitat, the exchange offers marine microbes a diverse palette of potential gene combinations, each of which might be best suited for a particular environment. "This would allow the overall population to persist despite complex and unpredictable environmental changes," said Chisholm.
A second report, by Zackary Johnson and Erik Zinser, compares where Prochlorococcus microbes are found with the conditions under which they thrive. These geographic patterns relate to environmental variables such as temperature, predators, light and nutrients.
Chisholm is trying to learn how the microbes function as a system in which they have co-evolved with each other, and with the chemistry and physics of the oceans. The studies show that all Prochlorococcus strains are very closely related, yet they display an array of physiologies and genetic diversity, Chisholm said.
"Genetic diversity is at the heart of the extraordinary stability of Prochlorococcus in the oceans, which maintain steady population sizes over vast regions of the sea," she said.