The samples recovered during IODP Expedition 385 offer the unique chance to study the interplay between thermochemical and biological processes at the upper temperature limit of life. Because sulfate reduction is the quantitatively most important process in anaerobic degradation of organic matter in marine sediments, this parameter is crucial for our understanding of carbon cycling in this system. The proposed project focuses specifically on quantification of sulfate reduction, and the effects of temperature and pressure on the microbial community. A special feature of Guaymas Basin are the extensive sills that intersect the organic-rich sediment. These sudden magmatic intrusions cause local heating of the sediment and thereby thermochemical cracking of otherwise non-bioavailable macromolecular organic matter. However, the extent of this heating effect is not known, is it just very localized and does not play any larger quantitative role, or do these sills alter biogeochemical conditions and processes on a larger scale? Your responsibilities include: quantification of biological turnover rates in deep sediments via incubation experiments with radioactive isotopes (35S, 14C, 3H); enrichment, cultivation and physiological experiments with subsurface microorganisms, using anaerobic cultivation techniques and high pressure equipment; geochemical analyses of samples and media using Ion Chromatography, Photometry, Tiration etc.; microscopy of microbial cells, using different techniques (FISH, CARD-FISH, BONCAT); publish in international peer-reviewed journals and present results at scientific meetings; co-supervise B.Sc. and M.Sc. students. We are looking forward to receiving your application by the August 7, 2020.