"How did the gaseous planets come to have so much atmosphere and so little solid surface?"
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Eukaryote Biodiversity and Physiology at Acidic Extremes: Spain's Tinto River
Project Investigators:
Other Project Members
Mitchell Sogin (Principal Investigator)Linda Amaral Zettler (Principal Investigator)Ricardo Amils (Principal Investigator)Felipe Gomez (Postdoc)Peter Smith (Collaborator)Katherine Hammar (Research Staff)Brendan Keenan (Research Staff)Astrobiology Roadmap Objectives:
- Objective 2: Develop and test plausible pathways by which ancient counterparts of membrane systems, proteins and nucleic acid were synthesized from simpler precursors and assembled into protocells.
- Objective 4: Expand and interpret the genomic database of a select group of key microorganisms in order to reveal the history and dynamics of evolution.
- Objective 6: Define how ecophysiological processes structure microbial communities, influence their adaptation and evolution, and affect their detection on other planets.
- Objective 7: Identify the environmental limits for by examining biological adaptations to extremes in environmental conditions.
- Objective 8: Search for evidence of ancient climates, extinct life and potential habitats for extant life on Mars.
Project Progress
This project aims to understand how microbial communities thrive under extreme conditions. Our study is based in the Tinto River located in southwestern Spain. The river is a high acid/metal environment with pH values between 2.0-2.5 and iron concentrations as high as 20 g/l. Algae contribute up to 65% of the total biomass of the community. This eukaryotic microbial community is understudied. Our project explores molecular eukaryotic diversity by looking at SSU rRNA genes and considers physiological adaptations allowing survival under pH extremes. Sequencing efforts have confirmed a strong algal component in the microbial community. Our molecular data reveal that certain biofilm-communities are dominated by phototrophs such as Chlamydomonad and Chrysophyte populations. Others are a complex assemblage of fungi, ciliate and flagellate populations. Still others are a combination of ciliate and diatom assemblages. Future work will focus on obtaining sequences from sediment samples from the Tinto and comparing sequence data with that from other acidic sites such as Davis Mine, an abandoned sulfuric acid mine in Massachusetts, and hot acidic furnas of the Azorean Islands. The physiology component of this project seeks to understand how pH-extremophiles maintain internal pH and whether there are different mechanisms by which internal pH is maintained by acidophiles. We have been making internal pH measurements using pH-sensitive indicators such as BCECF on algal cultures from the Tinto River. Our physiological experiments employ fluorescence ratio imaging and ion-selective probe technology accomplished at the single-cell level. Initial experiments conducted on cultures of Chlamydomonas sp. and Euglena sp. growing at pH 3 revealed striking differences between the two species. Our preliminary results show that Euglena sp. may have an internal pH below 6.5. In contrast, the internal pH of Chlamydomonas sp. appears nearer neutrality. The putative acidic values of Euglena sp. will be confirmed with alternative pH indicators.
Field Expeditions
NameTinto River - MBLDatesApril 1999 -LocationDescriptionThe purpose of the expedition was to obtain sediment and biofilm samples for DNA extraction, as well as to start enrichment cultures of acidophilic algae for use in physiological experiments to be accomplished in collaboration with Dr. Peter Smith of the BioCurrents Center at the Marine Biological Laboratory in Woods Hole, Massachusetts.- Ancestry of the earliest proteins
- Diversity and physiology of prokaryotes in selected thermophilic and mesophilic environments that might resemble early earth's biosphere
- Diversity of eukaryotes in thermophilic and mesophilic environments that might resemble early earth's biosphere
- Education and Public Outreach Activities
- Eukaryote Biodiversity and Physiology at Acidic Extremes: Spain's Tinto River
- Eukaryote origins and the evolution of cellular complexity - Eukaryotic rRNA evolution
- Eukaryote origins and the evolution of cellular complexity - Evolution of tubulins
- Genes that regulate photosymbiotic relationships
- Protist diversity in extreme environments
- Relationship of Genetic Changes to Phenotypic changes in Organism - Environment Interactions