Seminars & Events

Biosciences Division Seminar
"Microbial Diversity and Activity in Permafrost from the Canadian High Arctic"

DATE: April 13, 2007
TIME: 1:00pm
SPEAKER: Blaire Steven, Ph.D. Candidate, McGill University
LOCATION: Building 202, Room B169, Argonne National Laboratory
HOST: Deborah Hanson

Description:
Permafrost accounts for ~26% of terrestrial soil ecosystems, however, its biology, essentially microbiology, remains relatively unexplored. The permafrost environment is considered extreme because indigenous microorganisms must survive prolonged exposure to subzero temperatures and background radiation for geological time scales in a habitat with low water activity and extremely low rates of nutrient and metabolite transfer. Yet considerable numbers and diversity of microbes exist in permafrost, some of which may be among the most ancient viable life on Earth.

We have used a combination of culture-dependent and culture-independent techniques to produce the first comprehensive description of the microbial communities that inhabit Canadian high Arctic permafrost. Culturable bacteria from permafrost samples were predominantly related to spore-forming genera of bacteria belonging to the phylum Firmicutes, possibly suggesting that viable cells survived in a dormant state. Culture-independent surveys of the microbial diversity in permafrost revealed a diverse microbial community. In fact, the diversity of the microbial population in permafrost was not significantly different from that in the active layer soil.

In order to determine if the permafrost samples could support a functional microbial ecosystem we developed methods to detect and identify active microbes at in situ permafrost temperatures. Permafrost microcosms incubated at cold temperatures showed that microbial respiration was maintained at temperatures as low as -15°C. We are currently using stable isotope probing in an attempt to identify the psychroactive microbial communities.

These results will be important in defining the low temperature limits for microbial metabolism as well as determining if the search for microbes in other permafrost systems, including those beyond Earth, should be directed towards active microbial communities or frozen microbial fossils.

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