Genomic and in situ investigations of the novel uncultured Chloroflexi associated with 0092 morphotype filamentous bulking in activated sludge. Genome sequence for Ca. "Promineofilum breve" Cfx-K

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. Filaments with the Eikelboom 0092 morphotype are commonly associated with such bulking episodes. Members of the uncultured B45 phylotype, which is embraced within the phylum Chloroflexi, were recently shown to exhibit this morphology. Although these organisms are among the most abundant populations recorded in activated sludge processes, nothing is known about their metabolic characteristics. In this study, a genome sequence, representing the phylotype, was retrieved from a metagenome generated from an activated sludge WWTP plant. The genome consisted of two chromosomes and one plasmid, which were 4.0, 1.0, and 0.04 Mbps in size, respectively. A metabolic model was constructed for this organism, 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. The provisional name of Candidatus “Promineofilum breve” is proposed for this species. This study represents the first detailed information on an uncultured genus of filamentous organisms from activated sludge.