中文摘要：

缺氧的沉积环境中存在大量的细菌，它们消耗硫的化合物为其新陈代谢提供能量，并导致硫的化合物被还原、氧化或（和）歧化。细菌的还原作用和歧化作用都能造成明显的硫同位素分馏。细菌硫酸盐还原造成的硫同位素分馏一般在4‰-46‰之间，平均为21‰；细菌参与的氧化作用所造成的硫同位素分馏很小，不到5‰；硫的中间价态物质（S0、S2O3^2-和SO3^2-）的歧化作用可以造成7‰-11‰的硫同位素分馏。主要依据实验研究和现代海洋观测获得的细菌还原和歧化作用的硫同位素分馏结果已经被用于解释古代沉积物中的硫同位素记录，成为研究地球历史上古海洋的化学演化的重要手段。

英文摘要：

Plentiful bacteria are observed in anoxic sediments, where inorganic sulfur compounds can be reduced, oxidized, or/and disproportionately reacted by bacterial action and the bacteria acquire metabolic energy through those reactions. Bacterial reduction and disproportionation bring a significant isotope fractionation. For bacterial sulfate reduction （BSR）, in general, the isotope fractionation between sulfate and H2S ranges between 4‰ and 46‰, with an average of 21‰, but the isotope fractionation is small （less than 5‰） and negligible for bacterial sulfide oxidation. The bacterial disproportionation of the sulfur intermediates, such as S^0, S2O3^2- and SO3^2-, results in isotope fractionations of 7‰ - 11‰. The information of sulfur isotopic fractionation from cultural experiments and modern ocean investigations has been used to interpret sedimentary record and reconstruct chemical evolution of ocean in the Earth history.