sewage sludge bioreactor metagenome Metagenome

There is still a lack of information about microbial interactions of anaerobic digestion microbiome duringprocess disturbance which limits our ability to predict the mechanisms that drive community dynamicson these events. This paper aims to determine how an organic overloading affects these interactions andto characterize in detail the microbiome structure and diversity in sewage sludge anaerobic reactorsduring an acidosis event. Two identical sewage sludge anaerobic reactors were subjected to an organicloading shock by adding glycerol waste. As consequence, volatile fatty acids accumulated after only 24 h(up to 2.5 g/L) while Bacteroidales and Methanomicrobiales became displaced by Firmicutes and Methanosaetasp, showing that reactor acidosis can occur without an immediate decline of this methanogen.Network analysis revealed 9 clusters of co-occurring microorganisms with different behaviors duringoverloading. At first, Veillonellaceae family, the main glycerol degrading, associated with CandidatusCloacimonetes, volatile fatty acids fermenters, increased their relative abundance in detriment of thesyntrophic bacteria; although as conditions become more acidic, these groups were displaced by otherfermenters like Porphyromonadaceae and Chitinophagaceae. Eventually, the methanogenesis failed 72 hafter organic overloading, when pH reached values lower than 6. Overall, our results showed a successionof functionally redundant microorganisms, most likely because of niche specialization during organicoverloading. The detailed temporal analysis elucidated the processes governing the dynamics anaerobicdigestion microbiome, a knowledge required to develop anaerobic digestion management strategiesbased on its microbiome during process disturbances.