Mission 2009/2010

This will consist of an extended two-week field season at Tramway Ridge and potential single-day deployments to other high-temperature sites (see below).  At Tramway Ridge, soil samples will be taken at multiple high temperature sites (>65°C) and along the temperature gradient for geochemistry and DNA extraction.  These fresh soil samples will be used to inoculate select media directly in the field using the lower Erebus hut as a laboratory for cultivation experiments and transfers under controlled conditions.  Culturing capabilities will be transported to the site as necessary, including anaerobic chamber, gas cylinders, and incubators, etc.  As mentioned above, Year 2 will also include sampling of analogous high-temperature (65°C) soils along a latitudinal gradient, beginning at the southern part of South America (Chaiten volcano, Chile), and increasing in latitude to the South Shetland Islands (Deception and Thule), and two volcanoes (Mt. Melbourne and Mt. Rittman) near Terra Nova Bay.  Samples from South America, Mt. Melbourne and Rittman will be collected by the Cary team via Antarctica New Zealand deployments, whereas the sub-Antarctic island samples will be collected by our colleagues from the British, Italian, and Spanish Antarctic programs.

Results

Our second year of Marsden support has shown continued progress toward meeting our research objectives. We have independently tested methodology aimed at elucidating microbial community structure and applied this new methodology to our Tramway Ridge genetic analysis leading to a much better understanding of the structure of the tramway microbial community. We have identified a "core" set of organisms that dominate the ecosystem and have mapped the depth-­distribution of these organisms in Tramway Ridge soil. We have conducted deep-­?sequencing of metagenomic DNA using two different high-­throughput technologies. We have carried out initial analyses on this in­depth metagenome and used the information gained to create media designed to cultivate these dominant and elusive organisms. Our 2010/2011 field season was immensely successful and expanded our study beyond the borders of the Tramway Ridge protected area, sampling warm soils in ice caves and ice hummocks found around the summit of Mt. Erebus as well as the two other known sites of Antarctic geothermal activity, Mts Melbourne and Rittman. Temperature and relative humidity data loggers were positioned in key locations on the Tramway Ridge site and in ice caves that will be recovered next season providing an unprecedented view of the year round thermal nature of the system. Our key findings to date are:

  1. The structure of the subsurface community at Tramway Ridge is highly skewed, consisting of only a few highly abundant taxa and a much larger number of rarer taxa.
  2. Different sets of organisms are most abundant in either "shallow" or "deep" subsurface environments. The "shallow" subsurface appears to be dominated by organisms that are closely related to organisms typically found associated with geothermal microbial mats. However, the "deep" subsurface appears to be comprised mostly of organisms that are only distantly related to those found elsewhere.
  3. Deep­-sequencing has revealed the presence of a novel and potentially endemic Archaeal lineage that dominates the subsurface of Tramway Ridge. Large pieces of its genome can be identified in metagenomic datasets, reinforcing the finding that it is the most abundant organism in the "deep" subsurface.