121st General Meeting of the KCS

Type Symposium
Area Current Trends in Environmental and Energy Chemistry
Room No. Room 201B
Time THU 16:40-:
Code ENVR1-3
Subject Stable Isotope Geomicrobiology: Sub-cellular to Global
Authors Min Sub Sim
School of Earth and Environmental Sciences, Seoul National University, Korea
Abstract Microbes are involved in the vast majority of chemical and biochemical processes on the Earth’s surface, affect the environments that they live in, and leave geochemical signatures. While geologists have long used macrofossils to study the role of biology, recent advances in this field have expanded the signals of microbial life in the rock record beyond macrofossils to include molecular, elemental, and isotopic signatures. In this talk, I will focus on the application of sulfur isotope fractionation as a tracer for past microbial activities. Sulfur isotope fractionation between sulfate and sulfide has been used as a diagnostic indicator of microbial sulfate reduction, and a wide range of fractionations has attracted particular attention because it may serve as a potential indicator of environmental or physiological variables such as substrate concentrations or specific respiration rates. Depending on the organic electron donor, the resulting sulfur isotope enrichment factors vary between near-zero to 66‰, and disruptions in the electron delivery to the respiratory chain yield larger sulfur isotope fractionation. Direct assessment of intracellular processes, such as in vitro enzyme-specific studies and isotope measurements on key intermediates, has emerged recently as a promising means of addressing the details of isotope fractionation during microbial sulfate reduction. For example, sulfur isotope fractionation by APS reductase, the first reductive enzyme in sulfate reduction pathway, is measured for the first time to be 20‰. Given the presence of sedimentary proxies for seawater sulfate and sulfide isotopic compositions, all these findings can provide qualitative and quantitative constraints on the microbial sulfur cycle in the deep past as well as for the present.
E-mail mssim@snu.ac.kr