Soil microbes pool their resources and form surface attached colonies to better cope with large fluctuations in hydration status and diffusion fluxes. These bio-structures are made of exopolymeric substances (EPS), biopolymers composed of polysaccharides and proteins excreted by microbes to provide anchoring, entrap nutrients, and mediate between external soil hydrological conditions and eco-hydrological conditions in the immediate environment of microbial cells. We will focus on the micro-hydrological functions of EPS enabling microbial activity in the presence of extreme spatial and temporal variations in hydration status. The water retention and other key transport properties (nutrient diffusion) of EPS are critical to the universal success of this bio-porous medium. Shrink-swell behavior with changes in soil hydration and details of hydraulic interfacing with soil films in equilibrium and during rapid wetting drying events will be explored quantitatively. Morphological changes in EPS during rapid drying and potential role in evaporation retardation will be illustrated.