nai

Project Progress

One of the goals of the Astrobiology Roadmap is to explore the limits of life on Earth as analogues for environments on Mars, Europa and other planets that might support life. Our current research centers on such an analog: the Rio Tinto, a 100 km long river in southwestern Spain, has a pH range of 1.7-2.5, high concentrations of heavy metals, and an iron content that is thought to resemble conditions that may exist on Mars. Our recent small-subunit ribosomal ribonucleic acid (rRNA)-based studies reveal unexpectedly high eukaryotic phylogenetic diversity in the river. These studies identify organisms that live under acid/high metal extremes but tell us little about how these organisms have adapted to such environments. We are currently focusing on exploring the alterations in physiological mechanisms that might allow for growth of eukaryotic microbes at acid extremes. To this end we have isolated divergent protists from the Rio Tinto such as Chlamydomonas sp., Euglena cf. Mutabilis, Chlorella sp., and a lobose amoeba, assigned to the genus Vannella. – We are currently isolating and characterizing ion-transporting ATPases in the chlamydomonad, euglenid and vannellid amoeba and comparing these genes with those from neutrophilic counterparts obtained from culture collections. We have conducted polymerase chain reaction (PCR) experiments with primers designed to target the phosphorylation and ATP-binding sites found in members of the P-type ATPase superfamily. After cloning and sequencing these PCR products, we have determined that some of our clones fall into the heavy-metal P-type class but others may represent different ion transporters. We predict that special properties of these ion transporters allow protists to survive in the Rio Tinto’s extreme conditions.