The use of sedimentary archives for paleoclimatic and paleoenvironmental reconstructions can be hampered by diagenetic processes. Most of these processes are mediated (passively or actively) by microbial communities that are present in the different stages of sediment burial and formation. They encompass differential degradation of organic matter, changes in redox states of key elements like sulfur, iron or manganese, and dissolution and precipitation of mineral phases such as carbonates, sulfides, phosphates, sulphates, etc. Microbially mediated dissolution, precipitation, and transformation of minerals are either directly controlled by microorganisms or induced by biochemical reactions that usually take place outside the cell. A good understanding of these microbial processes is, thus, necessary to access the full potential of lake and ocean sedimentary archives. In this session, we invite all contributions that discuss the effects of microbial communities on sedimentary archives with approaches involving organic matter characterization (biomarkers), isotope biogeochemistry and omics methods. Works that advance our understanding of microbial activity in sedimentary framework (mineral-microbe interactions) and biomineralization processes through in-situ or ex-situ experiments are very welcome. Exploratory studies that link the deep biosphere to their environment in particular within the IODP and ICDP framework are also encouraged. We hope to gather a range of pluridisciplinary contributions that will allow to reinforce the cooperation between microbiologists, geochemists and sedimentologists in lake and ocean sediment studies.