A metabolic model for the 0092 morphotype associated with filamentous bulking problems in wastewater treatment plants

Overgrowth of filamentous bacteria in activated sludge wastewater treatment plants (WWTPs) leads to impaired sludge settleability, a condition known as bulking, which is a common operational problem worldwide. The B45 genus-level-taxon, exhibiting the Eikelboom 0092 bulking filament morphotype, is among the most abundant members of the phylum Chloroflexi in activated sludge, yet nothing is known about their metabolic characteristics. In this study, a genome sequence representing the B45 genus was assembled from a metagenome generated from a full-scale activated sludge WWTP. A metabolic model was constructed, based on annotation of its genome, showing its ability to generate energy by aerobic respiration, utilizing oxygen, nitrite, or nitrous oxide as electron acceptors, or by fermentation of sugars. This model was validated partially in situ. This study represents the first detailed information on an uncultured genus of filamentous organisms from activated sludge.