Soils host a vast biodiversity across various kingdoms, with multiple interactions within and between communities and with the surrounding environment. In this session, we will investigate how biodiversity in soils responds on biotic and abiotic factors across various spatial scales. We will study the functional roles of these communities in processes like nutrient and water cycling, trace gas exchange with the atmosphere, soil erosion, mineral weathering, and vascular plant germination and growth. We will put one special focus on extracellular polymeric substances (EPS) and their role in promoting microbial adhesion to surfaces, reducing cellular desiccation, protecting against antibiotics or toxic molecules, and even acting as a final source of nutrition under extreme scarcity. The amount, composition and functionality of EPS in soils, biological soil crusts, sediments or other porous media will be investigated. Responses of soil communities to land use and climate change as well as other potential threats will also be included in this session. Besides temperate soil communities, we will focus on biological soil crusts occurring in hot and cold deserts around the world, and biofilms forming in coastal regions of freshwater and marine environments.