MiDAS: A curated database for the microorganisms of activated sludge and anaerobic digesters

A deep understanding of the microbial communities and dynamics in wastewater treatment systems is a powerful tool for process optimization and design (Rittmann et al., 2006). With the advent of amplicon sequencing of the 16S rRNA gene, the diversity within the microbial communities can now be sampled sufficiently to describe the composition and dynamics of the most abundant organisms (Caporaso et al., 2012). However, to understand the relationship between the population dynamics and operational parameters of the system, a functional role must be attributed to each organism. A putative function can be proposed by classifying 16S rRNA gene amplicons to a genus or species, which has been characterized and for which the typical function in the ecosystem is known. Classification is usually done by comparison of the unknown sequences to a known reference set with a defined taxonomy. Public reference databases are large and the coverage of the known sequence diversity extensive. Presently, taxonomic annotation is a manual task and improving annotation across the entire microbial database is a substantial undertaking. A provisional solution has been to focus manual annotation on those organisms that are abundant in a particular habitat i.e. the Human Oral Microbiome Database (HOMD)(Chen et al., 2010). The Microbial Database for Activated Sludge (MiDAS) and Anaerobic Digesters presented here provides a curated taxonomy for abundant and important microorganisms and integrates it into a community knowledge web platform about the microbes in activated sludge and their associated ADs. 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.