This project studies the microbial processes that alter volcanic glass, which is critical to understanding the earliest life on earth. To understand the environmental controls on these processes, this project uses the extreme environments of the McMurdo region of Antarctica as a natural laboratory. Volcanic glass substrates are placed in hydrothermal systems, lakes, and other areas for two to four years to identify colonizing microbial consortia and the chemical processes of microbe-glass interaction. Recovered experiments are analyzed to explore the role of eukaryotic and prokaryotic organisms, and the relevance of autotrophs during colonization and biofilm formation using microscopic, molecular and culture techniques.
The broader impacts include graduate and undergraduate student participation in research and K-12 outreach and teacher training.
The exclusively microbial biosphere beneath the Earth’s surface has garnered substantial interest in recent years yet the biodiversity of and energy sources that support these communities is poorly understood. The main goal of this collaborative project was to investigate microbially-mediated alteration of volcanic glass using the extreme environments near McMurdo, Antarctica as natural laboratories, in particular the 3794 m high Mt. Erebus volcano, the McMurdo Dry Valleys and their lakes, Walcott Glacier in the Royal Society Range and McMurdo Sound. Our study aimed at exploring how these extreme environments influence the biological, chemical and physical characteristics of glass bioalteration. Dark, organic-poor environments are particularly interesting to explore types of metabolisms that obtain their energy entirely from inorganic chemicals rather than from sunlight. They also provide an analog of the oxic subsurface ecosystems that account for about 50% of oceanic sediments, yet they differ because they are largely uncontaminated by external organic inputs and are more accessible to careful sampling and experimental work. Our project was based on experiments in which we exposed volcanic glasses of different composition to natural settings and collected parallel samples for baseline studies of the natural soils and waters. We studied microbial colonization, biofilm formation and the alteration of well-characterized glasses, in a time series of two and four years. For comparative purposes, our work focused on settings that range from hot to extremely cold, dark to light, and saline to fresh water. We also examined more organic-rich environments such as the Dry Valleys lakes and the seawater in McMurdo Sound where metabolisms based on organic energy sources may be important in glass alteration. Our field work paid equal attention to all extreme environments but the data reduction and microbiological studies supported by the Oregon Health & Science University part of the project focused mainly on samples collected in Mt. Erebus ice caves. We were able to access the caves safely and recover most of our 2 and 4 year experiments despite their limited access and our worry that the caves would not be stable from year to year. Our temperature logs for two of the caves proved that these environments are thermally stable more than 95% of the time, without significant seasonal variation. We were able to isolate cultures of bacteria that could oxidize iron, manganese and carbon monoxide. Studies using molecular microbiological approaches to assess the diversity of microbial communities without the need for cultivation demonstrated: 1) a very low diversity of bacteria in the dark caves compared to a low to moderate diversity of bacteria in caves encountering light; 2) an abundance of organisms with the genes for a key carbon dioxide-fixing enzyme found in autotrophic organisms but which represent very novel and more ancient forms; and 3) from an analysis of the DNA sequence of the entire community present in a sample (the metagenome) the community derives most of its energy from carbon monoxide oxidation, assimilates nitrogen from oxidized forms of nitrogen (nitrate or nitrite), and does not fix nitrogen gas. Overall these results demonstrate that geochemical energy sources, especially those from volcanic emissions, are providing the basis for the microbial food web in the dark ice caves. These results provide important baseline data for the evaluation of the microbial communities colonizing and altering the volcanic glasses in our exposure experiments. Initial analyses of some of those experiments were conducted but more detailed analysis is required and will be the subject of future research. Intellectual merit: The work explored linkages between the biosphere, hydrosphere and lithosphere, a topic of research at the frontier of earth, life and environmental sciences. Contributing to an understanding of these processes and linkages is fundamental to a variety of ecosystem processes, for example, from food webs to the geochemical exchange between the mantle and the hydrosphere. The research also contributed to our understanding of life in extreme environments, microbial adaptations to extreme organic-poor conditions and microbial biodiversity. In particular it provided new insights into microbial communities dependent on chemical as opposed to photosynthetic energy as the basis of the food web. Broader impacts: A variety of education and outreach activities were undertaken. Two graduate students participated in both Antarctic field research and laboratory research. In addition one high school student and three undergraduate students participated as research interns. One graduate student and one summer intern were from groups underrepresented in science. The results of the research were communicated through publications, presentations at national meetings, and a web blog that was maintained during the field research.
