LEXEN: Adaptations of Unicellular Eukaryotes to Extremely Acidic Environments

Marine Biological Laboratory, Woods Hole MA

Investigators

Abstract

DEB-0085486 Mitchell Sogin Dr. Mitchell Sogin of the Marine Biological Laboratory at Woods Hole, MA has been awarded a grant to study the adaptation of eukaryotic microorganisms to extremely acidic environments. Studies of life in extreme environments rarely focus upon eukaryotic microbes. Yet there is clear evidence that protists inhabit and sometimes dominate ecosystems that are either very acidic or very alkaline. A particularly interesting system is the Rio Tinto, a river basin in southwestern Spain. This is an acidic environment where the pH ranges from 1.7-2.5 and iron concentrations are as high as 20 mg/ml. The river does not directly support multi-cellular animals but it is teeming with eukaryotic microbes, sometimes representing as much as 65% of the biomass. The goal of this proposal is to define protist diversity in the Rio Tinto and to explore alterations in physiological mechanisms that might allow the growth of eukaryotic microbes in this extreme environment. Sogin's team will use a combination of culturing and molecular techniques to estimate protist diversity. Molecular studies of gene sequences that have been isolated from the Rio Tinto biofilm samples will provide estimates of protist diversity. These will be compared to the diversity of protists that can be brought into culture. They will also use the culture isolates to explore natural variation in physiological properties that underlie the stability of acidophilic protist populations. We will determine what modifications to existing eukaryotic mechanisms are necessary for growth at extremely low pH and how eukaryotes have adapted to extreme acid environments.