Genomic insights into three new provisional candidate lineages involved in nitrate and nitrite reduction in EBPR enrichment cultures. Nitrate reduction in EBPR

Genome-centric metagenomic analysis of three new provisional lineages of "Candidatus Accumulibacter delftensis", "Candidatus Nocardioides delftensis", and "Candidatus Thermomonas delftensis" from an EBPR system tested for denitrification on nitrate. Quantitative measurements of conversions in the enrichment cultures highighted that nitrate reduction did not occur concomittantly to biological phosphorus removal under anoxic conditions. Near-complete genomes from the main lineages present in the biosystem were retrieved from the sludge metagenome, and throroughly checked for their uniqueness versus all publically available genome assemblies of closest neighbours from on-line databases at the time of the study. Genome analysis highligted that "Candidatus Accumulibacter delftensis" is deprived of the respiratory nitrate reductase (nar) gene required for respiration with nitrate as terminal electron acceptor, but can run denitrification on nitrite. "Candidatus Nocardioides delftensis" and "Candidatus Thermomonas delftensis" which harbour nar genes, providing potential for interaction with "Candidatus Accumulibacter delftensis" on denitrification pathways.