Scientists at Pacific Northwest National Laboratory study the microbial interactions in the plant root systems, the rhizosphere. The rhizosphere represents a critical zone where plant roots, microbes and minerals interface, and where biogeochemical weathering provides nutrients to plants. This research program will broaden our understanding of the biogeochemistry of plant-microbe-soil interactions. Shown are the spores of an opportunistic soil fungus Penicillium sp. that associates with the plant roots, microbial biofilms and soil minerals.