Abstract
Anaerobic ammonium oxidation (anammox) is a promising option for removing nitrogen from wastewater. We aimed to compare anammox bacteria from samples of freshwater environmental sludge (river, lake, and dam reservoir) cultivated under mesophilic (35℃) and psychrophilic (15℃) conditions. An increase in nitrogen removal rate (NRR) was found in the mesophilic condition after 400 days cultivation, whereas no significant increment was detected in the psychrophilic condition. After additional cultivation for over 400 days, NRRs values increased to almost same levels of those of mesophilic condition. Phylogenetic analysis showed that 4 anammox clonal phylotypes could be categorized from 6 samples from anammox reactors, and most phylotypes were shared among multiple samples. Phylotypes of the mesophilic samples had 99% and 100% identity with Candidatus Jettenia caeni strain KSU－1 and Candidatus Brocadia sinica strain JPN1, respectively, whereas phylotypes of psychrophilic samples showed 94% and 96% identity with Candidatus Brocadia fulgida and Candidatus Brocadia sp. 40, respectively. Cultivation temperature affected enriched anammox species. Furthermore, phylotypes of psychrophilic samples were categorized into psychrophilic anammox group of Brocadia lineage, indicating the existence of low temperature-adapting anammox bacteria.
