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Project Progress

We have been focusing on the eukaryotic diversity in Spain’s Rio Tinto (Red River), a 90 km river that flows through one of the world’s largest pyritic belts. The river is an example of a high acid / heavy-metal extreme environment that gets its red color from the high levels of iron dissolved in its acidic waters (pH ~2.0). In addition to iron, which can be as high as 20 g/l, the river also contains other heavy metals at concentrations orders of magnitude higher than those that occur in typical freshwater environments.

Our recent small-subunit rDNA-based studies, which constitute the first molecular description of eukaryotic diversity in an acidic/high-metal environment, reveal an unexpectedly high eukaryotic phylogenetic diversity with several novel taxa, as well as cosmopolitan organisms never before reported from acidic/high-metal extremes. Our molecular data detected many additional non-photosynthetic lineages such as ciliates, cercomonads, vahlkampfiid amoebae, stramenopiles, and fungi that had escaped detection by traditional methods. This is in contrast to relatively low prokaryotic diversity that has been detected by DGGE and in situ hybridization methods used by colleagues in Spain to access prokaryotic diversity.

These studies identify organisms that live under acidic/high-metal extremes but tell us little about how these organisms have adapted to such environments. The next phase of our work focuses on exploring the alterations in physiological mechanisms that might allow for growth of eukaryotic microbes at acid extremes. To this end we are isolating divergent protists such as diverse amoebae, diatoms (stramenopiles), and ciliates (alveolates). We are currently isolating and characterizing ion-transporting ATPases in a cultured chlamydomonad and euglenid and comparing these genes with those from neutrophilic counterparts. To date we have partially sequenced members of the heavy-metal transporting ATPase family. We predict that special properties of these ion transporters allow protists to survive in the Rio Tinto.