A Microbial Consortium Removing Phosphates under Conditions of Cyclic Aerobic-Anaerobic Cultivation

Abstract

Formation of a community of phosphate-accumulating microorganisms in a laboratory sequential batch reactor (SBR) ensuring alternated aerobic and anaerobic conditions during periodic removal and addition of the medium were investigated. The bioreactor removed 50% phosphorus from the incoming medium after 22 days from the start-up. Microscopy and X-ray microassay revealed the of cells of diverse morphology that contained phosphorus-enriched granules. High-throughput sequencing of the 16S rRNA gene fragments carried out on days 0, 8, 15, and 22 showed changes in the community composition and its decreasing diversity. On day 22, approximately twofold increase of the relative abundances of Bacteroidetes (up to 43% of the 16S rRNA gene sequences) and Proteobacteria of the classes alpha (up to 15%) and beta (up to 27%) was observed. While at the onset of the reactor operation, typical PAOs related to “Candidatus Accumulibacter” (class Betaproteobacteria) constituted 0.2% of the community, they were not detected on day 22. The most likely PAO candidates were beta-proteobacteria of the genus Dechloromonas, the share of which increased from 0.7 to 11% by the time of the highest phosphorus removal from the inflowing medium. The relative abundance of heterotrophs of the genus Zoogloea (family Rhodocyclaceae) increased from 0.1 to 11.5%.