Probing Korachaeal ecophysiology via statistical analysis of quantitative molecular and geochemical data: A RIDGE2000 postdoctoral proposal

Harvard University, Cambridge MA

Investigators

Abstract

This project describes an integrative study of distribution and abundance of the Korarchaeota in hydrothermal vent chimneys. Diverse microbial communities representing a wide array of metabolic capacities inhabit the extreme environments of deep-sea hydrothermal vents. The high diversity in these communities is largely a result of high microhabitat variability along gradients in temperature, mineralogy, and geochemistry from the inner, hydrothermally influenced surfaces on the inner walls of the chimney to the near ambient conditions of the outer walls. Although the microbial diversity has been described in these habitats, information on the quantitative distribution and abundance of microbes within the chimney walls is largely lacking. In order to understand the function of these communities and the potential links from mantle to microbe and subsurface to surrounding deep-sea, the distribution, abundance, and metabolic capacity of microbial populations within the chimneys that span these gradients are required. One of the largest gaps in our understanding of these microbial communities lies in the largely uncharacterized archaeal group, the Korarchaeota. This proposal describes a rigorous statistical framework for relating the distribution and abundance of korarchaeote phylotypes to temperature and geochemical data from hydrothermal vent chimneys. This work will use data gathered from novel in situ incubation devices implanted in sulfide chimneys on the Endeavor segment of the Juan de Fuca ridge by collaborating laboratories. Incubation devices are titanium tubes lined with substrates (e.g. pyrite) and equipped with temperature sensors and in situ fluid sampling devices, which are placed into 5 cm diameter holes drilled in the sides of sulfides (chimneys). These devices were implanted as part of an ongoing study at the Endeavor Integrated Study Site. Clone libraries will be developed from the chimney cores obtained during drilling. These libraries will be used to develop and test primers for the korarchaeote phylotypes present. After recovery of the inserts, incubated substrates will be analyzed via quantitative PCR to enumerate korarchaeote phylotypes. These data will allow us to relate the distribution and abundance of the Korarchaeota to the geochemical and temperature profiles generated by collaborating laboratories. The intellectual merit of the proposed research lies in the provision of quantitative data on the diversity, distribution and abundance of the Korarchaeota in the vent habitat. This study will also define the realized niche of the Korarchaeota within hydrothermal vent chimneys, providing new statistical modeling tools that will be used to refine current hypotheses and focus future studies of the potential metabolic capacities of korarchaeote phylotypes in vent communities. The broader impacts of this study include the training of a newly appointed faculty member and a post-doctoral researcher in new fields of study. This collaboration between Dr. Girguis and Dr. Cordes will provide the first quantification of the Korarchaeota in the hydrothermal vent habitat and will lead to the formation of tractable hypotheses for the metabolic capacity of korarchaeote phylotypes. Dr. Cordes will work with the SEAS program within Ridge2000 to develop a Classroom to Sea laboratory to relate this research to middle and high school students.