In Situ Activity and Spatial Organization of Anaerobic Ammonium-Oxidizing (Anammox) Bacteria in Biofilms

Abstract

We investigated autotrophic anaerobic ammonium-oxidizing (anammox) biofilms for their spatial organization, community composition, and in situ activities by using molecular biological techniques combined with microelectrodes. Results of phylogenetic analysis and fluorescence in situ hybridization (FISH) revealed that "Brocadia"-like anammox bacteria that hybridized with the Amx820 probe dominated, with 60 to 92% of total bacteria in the upper part (<1,000 m) of the biofilm, where high anammox activity was mainly detected with microelectrodes. The relative abundance of anammox bacteria decreased along the flow direction of the reactor. FISH results also indicated that Nitrosomonas-, Nitrosospira-, and Nitrosococcus-like aerobic ammonia-oxidizing bacteria (AOB) and Nitrospira-like nitrite-oxidizing bacteria (NOB) coexisted with anammox bacteria and accounted for 13 to 21% of total bacteria in the biofilms. Microelectrode measurements at three points along the anammox reactor revealed that the NH 4 ؉ and NO 2 ؊ consumption rates decreased from 0.68 and 0.64 mol cm ؊2 h ؊1 at P2 (the second port, 170 mm from the inlet port) to 0.30 and 0.35 mol cm ؊2 h ؊1 at P3 (the third port, 205 mm from the inlet port), respectively. No anammox activity was detected at P4 (the fourth port, 240 mm from the inlet port), even though sufficient amounts of NH 4 ؉ and NO 2 ؊ and a high abundance of anammox bacteria were still present. This result could be explained by the inhibitory effect of organic compounds derived from biomass decay and/or produced by anammox and coexisting bacteria in the upper parts of the biofilm and in the upstream part of the reactor. The anammox activities in the biofilm determined by microelectrodes reflected the overall reactor performance. The several groups of aerobic AOB lineages, Nitrospira-like NOB, and Betaproteobacteria coexisting in the anammox biofilm might consume a trace amount of O 2 or organic compounds, which consequently established suitable microenvironments for anammox bacteria.Anaerobic ammonium oxidation (anammox) is a microbiological oxidation of ammonium, with nitrite as the electron acceptor and dinitrogen gas as the main product, and is mediated by a group of deep-branching Planctomycete-like bacteria (12, 39). Anammox bacteria have been detected in different wastewater treatment facilities and environments in the world (for a review, see reference 34). Currently, four genera of anammox bacteria have been reported and named, including Brocadia, Kuenenia, Scalindua, and Anammoxoglobus (14,34).The anammox process is a new and promising alternative to conventional nitrogen removal processes. A better understanding of the ecophysiology (i.e., microbial community structure and in situ activity) of anammox bacteria in complex biofilms is essential for implementing the anammox process as a manageable and reliable nitrogen removal process in wastewater treatment. However, related information is limited because anammox bacteria are strict anaerobic autotrophs and thus have not yet been isolate...

Environmental Factors Shape Sediment Anammox Bacterial Communities in Hypernutrified Jiaozhou Bay, China

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The Zeolite-Anammox Treatment Process for Nitrogen Removal from Wastewater—A Review

“…Originally considered to be inhibited by organic matter, some anammox species are less inhibited by carbon [46] and some of the most recently discovered species flourish when organic matter is present. Kindaichi [47] postulated that anammox was inhibited by COD; but probably a result of species, pH, temperature, type of carbon, and C:N ratio. Molinuevo's work [48] appeared to indicate that organic matter at high COD concentrations (100 to 250 mg COD/L) negatively affected the anammox process and facilitated heterotrophic denitrification, but at COD concentrations < 100 mg/L, anammox bacteria successfully converted ammonium to nitrogen gas suggesting that anammox removal of nitrogen of already treated wastewater having low COD is quite possible.…”

Enrichment Using an Up-flow Column Reactor and Community Structure of Marine Anammox Bacteria from Coastal Sediment

“…Furthermore, the cultures showed a low population density (67-90% of total bacteria) and/or low conversion rates (0.07-0.35 g L −1 day −1 ) after long periods of enrichment. We previously reported that anammox bacteria derived from wastewater were successfully enriched using up-flow fixed-bed column reactors, and that the anammox reaction was observed within 2-3 months after the reactor start-up (14,33). These studies were conducted based on strategies specific for the selected inoculum and a short hydraulic retention time (HRT).…”