From Early Biospheric Metabolisms to the Evolution of Complex Systems

As a returning member of the NASA Astrobiology Institute, the MBL Astrobiology team works toward understanding the patterns and mechanisms of genome evolution and metabolic variation that allowed diverse microorganisms to adapt to new environments, generate novel phenotypes, and effect global- scale changes detectable by remote sensing. In addition to providing increased knowledge about evolutionary history of life on Earth, our studies will provide a basis for interpreting telemetry data and developing life detection technology for planetary exploration. Our general strategy emphasizes the integration of molecular approaches to evolutionary biology with studies of metabolic activities in environments that most likely reflect conditions on early Earth.  Our physiological and microbial diversity studies focus on the hydrothermally altered sediments of Guaymas basin in the Gulf of California, the acidic, heavy metal laden Rio Tinto of southwestern Spain and isolates from the Juan de Fuca Ridge.

Interdisciplinary research projects encompass four major themes:

1. Earth's Early Biosphere: Evolution of microbial physiologies

   Andreas Teske, Stefan Sievert, Virginia Edgcomb, Ashita Dhillon

   Classical, ribosomal (rRNA) phylogenies alone cannot inform us about the early evolution of microbial metabolisms and pathways. We are exploring the physiological history of early microbial life in the context of early biogeochemical evolution of the biosphere through studies of genes for conserved enzymes with well-defined physiological roles.

   Focus areas include:
   

   • Exploration of the origin and diversification of ancient pathways particularly sulfate reduction and methanogenesis in sediments of Guaymas basin and other environments
   • Determination of the evolution and diversity of ancient carbon dioxide fixation pathways in anaerobic and extremophilic microorganisms.

2. Terrestrial Analogues for Early Mars: Biology of Iron oxidation, Microbial Populations in Rio Tinto, and Life detection through remote sensing

   Linda Amaral Zettler, Mitchell Sogin, Katrina Edwards, Andreas Teske, Jack Mustard, Jim Head, Ashita Dhillon,

   The presence of extensive iron deposits (banded iron formations or BIFs) dating back to the Archean and the broad distribution of proteins with FeS centers in all organisms indicate the importance of iron and Fe cycling for early life forms. Our astrobiology team explores microbial Fe metabolism in prokaryotes from metal sulfide deposits at Juan de Fuca Ridge as well as microbial population structures in the acidic, Fe-rich environment of Rio Tinto. These environments represent potential analogues for an early, wetter Mars. Our interdisciplinary team of biologists and planetary geologists will incorporate new information from these studies into the design of life detection through remote sensing. We are also carrying out expression profiling experiments of oxygenic cyanobacteria from microbial mats with the goal of understanding the molecular basis of adaptation to extreme environments and the use of microarray technology in studying microbial communities in extreme environments.

   Project investigation areas include:
   

   • The fundamental biology of Fe oxidation in mesophilic and extremophilic microorganisms, and its relationship to geochemical processes. (External link.)
   • Genome biology of neutrophilic iron oxidizing bacteria
   • Community surveys of the microbiota from Rio Tinto based upon SAGT, a newly developed technique for high-throughput analyses of rDNA sequences
   • Use of minerals from iron-rich, acidic environments as biosignatures for remote sensing
   • Expression profiling and the formation of biogeochemical gradients in cyanobacterial mats and in extreme environments .

3. Biosignatures and Life Detection: Detecting ancestral peptides and proteins

   Norman Wainwright, Rebecca Gast

   Members of protein super families share ancestral conserved functional domains. Taking advantage of what is known about conserved domain sequences, we will develop a miniaturized instrument for the detection of ancestral peptides and nucleic acid sequences.  The detection system will be adapted from extremely sensitive enzyme cascade reaction technology that detects the presence of bacterial lipopolysaccharides.

   Projects and focus areas include:
   

   • Identifying appropriate key ancestral sequences in E. coli gene families
   • Designing appropriate probe sequences, hybridization and detection assays
   • Developing a miniaturized instrument for amplified life detection.

4. Evolution of Genome Architecture in Prokaryotes and Eukaryotes: Symbiosis, genome-genome integration, and evolutionary innovation

   Jennifer Wernegreen, Seth Bordenstein

   Genome-genome interactions have been a driving force in the evolution of early life, the origin of eukaryotes and the evolution of multicellular complexity.  These interactions foster lateral gene transfer between organisms and the remodeling of genome architecture.Using a genomic scale approach, we will study changes in genome structure and expression patterns for endosymbiotic associations between bacteria and eukaryotic hosts.

   Projects and focus areas include:
   

   • Identifying changes in genome architecture, including lateral gene transfer, that catalyze endosymbiont-host interactions and contribute to their current diversity.
   • Examining plasticity of gene expression in genome-genome interactions.

Educational and Public Outreach

A newly formed joint Brown-MBL graduate training and research program will allow PhD students to pursue astrobiology-relevant research topics in molecular ecology, evolutionary biology and genome science at the MBL.

The MBL offers two advanced training courses of interest to Astrobiologists: Workshop on Molecular Evolution and Advances in Genome Technology and Bioinformatics .

Teacher professional development courses help introduce middle and high school teachers to the importance of microbes and astrobiology and provide them with appropriate hands on activities for the classroom. We offer Living in the Microbial World, a one-week intensive course in the summer, and Discover the Microbes Within!, a three day workshop, in the Spring.

Through NAI, we have developed micro*scope, an image-rich web database structure for microbial diversity. Micro*scope will further develop tools for archiving and integrating image-rich data from habitats currently being studied by astrobiologist.