Provides a curated taxonomy for abundant and important microorganisms and integrates it into a community knowledge web platform about the microbes in activated sludge. The MiDAS taxonomy proposes putative names for each genus-level-taxon that can be used as a common vocabulary for all researchers in the field. The online MiDAS field guide links the identity of annotated genera to details about their morphology, diversity, physiology and distribution. MiDAS is intended as a collaborative workspace, available for researchers and wastewater treatment practitioners, to facilitate a better understanding of the ecology of this biotechnologically important ecosystem.