Genomic and Metabolic Insights into Two Novel Thiothrix Species from Enhanced Biological Phosphorus Removal Systems.

Two metagenome-assembled genomes (MAGs), obtained from laboratory-scale enhanced biological phosphorus removal bioreactors, were analyzed. The values of 16S rRNA gene sequence identity, average nucleotide identity, and average amino acid identity indicated that these genomes, designated as RT and SSD2, represented two novel species within the genus Thiothrix, 'Candidatus Thiothrix moscowensis' and 'Candidatus Thiothrix singaporensis'. A complete set of genes for the tricarboxylic acid cycle and electron transport chain indicates a respiratory type of metabolism. A notable feature of RT and SSD2, as well as other Thiothrix species, is the presence of a flavin adenine dinucleotide (FAD)-dependent malate:quinone oxidoreductase instead of nicotinamide adenine dinucleotide (NAD)-dependent malate dehydrogenase. Both MAGs contained genes for CO2 assimilation through the Calvin-Benson-Bassam cycle; sulfide oxidation (sqr, fccAB), sulfur oxidation (rDsr complex), direct (soeABC) and indirect (aprBA, sat) sulfite oxidation, and the branched Sox pathway (SoxAXBYZ) of thiosulfate oxidation to sulfur and sulfate. All these features indicate a chemoorganoheterotrophic, chemolithoautotrophic, and chemolithoheterotrophic lifestyle. Both MAGs comprise genes for nitrate reductase and NO-reductase, while SSD2 also contains genes for nitrite reductase. The presence of polyphosphate kinase and exopolyphosphatase suggests that RT and SSD2 could accumulate and degrade polyhosphates during the oxic-anoxic growth cycle in the bioreactors, such as typical phosphate-accumulating microorganisms.

Metagenomic data of the microbial community of lab-scale nitritation-anammox sequencing-batch bioreactor performing nitrogen removal from synthetic wastewater.

The nitritation-anammox process, which involves partial aerobic oxidation of the ammonium to nitrite and following oxidation of ammonium by nitrite to molecular nitrogen, is an efficient and cost-effective approach for biological nitrogen removal from wastewater. To characterize the microbial communities involved in the nitrogen and carbon cycles in wastewater treatment bioreactors employing this process, we sequenced the metagenome of a sludge sample collected from the lab-scale nitritation-anammox sequencing-batch reactor. At the phylum level, Proteobacteria and Chloroflexi were the most numerous groups. Anammox bacteria belonged to the genus Candidatus Brocadia. The obtained data will help to investigate the taxonomical and functional diversity the microbial communities involved in nitritation-anammox process, and will be used for genome-based analysis of uncultured bacterial lineages. The raw sequencing data is available from the NCBI Sequence Read Archive (SRR9831403) database under the BioProject PRJN0A55627.