Investigating the Physiological and Metabolic Requirements of the Tramway Ridge Microbial Community, Mt Erebus, Antarctica

Abstract

Mount Erebus is the most active volcano on the Antarctic continent, and has the most geographically and physically isolated geothermal soil on Earth. It is exposed to some of the most extreme environmental conditions on the planet. Recent preliminary genetic analysis of the microbial community present in the 65°C subsurface soil of Tramway Ridge, Mount Erebus has revealed a unique thermophilic microbial system, with the dominant members possessing little genetic similarity to any known bacteria. The aim of this project was to apply a range of techniques to investigate metabolic and physiological requirements of this poorly understood microbial system. The study included physical-chemical soil surveying, strategic cultivation, community based phenotypic arrays, nutritional enrichment experiments and pyrosequencing. This multifaceted, metabolism driven, approach incorporated both culture dependent and culture independent techniques in order to investigate the intriguing system in a way that is crucial to the understanding of this thermophilic community and the controlling environment. Overall, the results of this study have led to the hypothesis that the Tramway Ridge microbial community is driven by chemolithoautotrophic microorganisms. This hypothesis is supported by a number of observations, firstly that in the absence of carbonate in enrichments, the community shifts to being dominated by obligate heterotrophs; the microbial ecosystem exists in subsurface soils which have limited, or no, light availability; the system is nutrient poor in nature, coupled to a carbon dioxide dominated gas supply from volcanic activity; two of the keystone members identified from pyrosequencing, phylogenetically group with bacterial phyla known for chemolithoautotrophic metabolism. Considering the detailed investigation of this apparently archaic and isolated microbial system, there is potential for this study to become an excellent model for future studies addressing the fundamental functioning and evolutionary processes associated with other thermophilic communities.