Characterization of Enrichment Cultures of Anammox, Nitrifying and Denitrifying Bacteria Obtained from a Cold, Heavily Nitrogen-Polluted Aquifer

• Published in: Biology (Basel, Switzerland) Switzerland), 2023-01, Vol.12 (2), p.221
• Main Authors: Botchkova, Ekaterina, Vishnyakova, Anastasia, Popova, Nadezhda, Sukhacheva, Marina, Kolganova, Tatyana, Litti, Yuriy, Safonov, Alexey
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonia-oxidizing bacteria; Ammonium; Anaerobic bacteria; Anaerobic conditions; Analysis; anammox bacteria; aquifer; Aquifers; Bacteria; Batch culture; Bioremediation; Carbon; Cellulose acetate; Cold; Denitrification; Denitrifying bacteria; Drinking water; Ecosystems; Enrichment media; Fed-batch culture; Genera; Groundwater; heavy nitrogen pollution; Low temperature; Microorganisms; Nitrates; Nitrifying bacteria; Nitrites; Nitrogen; Oxidation; Planctomycetota; Pollution; Radioactive wastes; Sludge; Solid wastes; Stoichiometry; Uranium; Wastewater treatment; Water treatment; Water, Underground; Xanthomonadaceae
• ISSN: 2079-7737; 2079-7737
• DOI: 10.3390/biology12020221

Anammox bacteria related to Scalindua were recently discovered in a cold (7.5 °C) aquifer near sludge repositories containing solid wastes of uranium and processed polymetallic concentrate. Groundwater has a very high level of nitrate and ammonia pollution (up to 10 and 0.5 g/L, respectively) and a very low content of organic carbon (2.5 mg/L). To assess the potential for bioremediation of polluted groundwater in situ, enrichment cultures of anammox, nitrifying, and denitrifying bacteria were obtained and analyzed. Fed-batch enrichment of anammox bacteria was not successful. Stable removal of ammonium and nitrite (up to 100%) was achieved in a continuous-flow reactor packed with a nonwoven fabric at 15 °C, and enrichment in anammox bacteria was confirmed by FISH and qPCR assays. The relatively low total N removal efficiency (up to 55%) was due to nonstoichiometric nitrate buildup. This phenomenon can be explained by a shift in the metabolism of anammox bacteria towards the production of more nitrates and less N at low temperatures compared to the canonical stoichiometry. In addition, the too high an estimate of specific anammox activity suggests that N cycle microbial groups other than anammox bacteria may have contributed significantly to N removal. Stable nitrite production was observed in the denitrifying enrichment culture, while no "conventional" nitrifiers were found in the corresponding enrichment cultures. was a common taxon for all microbial communities, indicating its exclusive role in this ecosystem. This study opens up new knowledge about the metabolic capabilities of N cycle bacteria and potential approaches for sustainable bioremediation of heavily N-polluted cold ecosystems.