High Temperature and Pressure (HTP) Reactor System for Understanding Physiology of Extremophiles at in situ Condition

Hydrostatic pressure constitutes one of the very basic, thus important parameters for life on Earth. High-pressure environments include the deep subseafloor, where microbial life have been discovered to exist in few to tens of percent of microbial biomass on Earth (1, 2). However, the microbial physiology in such hydrostatically pressured, and especially at high temperature environment, has been kept understudied despite of the many discoveries of extremophiles from such environments (3). In this study, we constructed High Temperature and Pressure (HPT) reactor system to conduct incubations at pressure up to 60 MPa and temperature of >100°C. The unique aspects of this HPT reactor system are (i) the capability of injecting microbial culture/substrates through external pressure syringe after the entire system reaches incubation (i.e. high pressure and temperature) condition (allows strict constrain of microbial metabolic activity under pressured condition), (ii) allowing sampling during incubation without changing incubation condition (monitoring "what's inside" without changing parameters), (iii) gold-made inner chamber can hold everything in chamber, including small molecules (such as hydrogen). At system performance test of the new HPT reactor with only media, stable concentration of hydrogen could have been maintained for month in the gold-based incubation chambers. Then we conducted cultivation of known extremophilic anaerobes of Pyrococcus yayanosii (obligate piezophile) and Archaeoglobus profundus (hyperthermophilic sulfate reducer). Detailed growth and nutrient characteristics over time will be discussed in the presentation. Whitman WB, Coleman DC, Wiebe WJ. 1998. Prokaryotes: The unseen majority. Proc. Natl. Acad. Sci. USA 95:6578-6583. Kallmeyer J, Pockalny R, Adhikari R, Smith D, D'Hondt S. 2012. Global distribution of microbial abundance and biomass in subseafloor sediment. Proc. Natl. Acad. Sci. USA 109:16213-16216. Stetter KO. 2013. A brief history of the discovery of hyperthermophilic life. Biochemical Society Transactions 41:416-420.