Nitrifying Microbial Community Research Articles

Comparison of nitrifying, denitrifying, and overall microbial communities in two constructed wetlands and two compact attached biomass reactors treating domestic wastewater

Comparison of nitrifying, denitrifying, and overall microbial communities in two constructed wetlands and two compact attached biomass reactors treating domestic wastewater

Identification of dominant microbial community in aerophilic biofilm reactors by fluorescence in situ hybridization and PCR-denaturing gradient gel electrophoresis

This study was conducted by combining fluorescence in situ hybridization (FISH) performed on 16S rRNA and polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) with 16S CTOs primers to characterize the nitrifying microbial communities in biofilm processes, which were tested to retrofit the S municipal wastewater treatment plant in Busan, Korea. Four aerophilic biofilm reactors were operated with hydraulic retention times of 2 to 8 h and biofilms were grown on ceramic media. The same low COD/ NH 4 + -N ratio (100 mg/L of COD over 40 mg/L of NH 4 + -N) with the S plant was used. The average relative population ratios of Nitrosomonas spp. to ammonia oxidizing bacteria (AOB) as measured by specific FISH probes (%/Nso190) were 75.0%, 80.0%, 73.0% and 73.5%, respectively, while those of Nitrosospira spp. to AOB were 21.0%, 14.7%, 24.6% and 24.1% after 180 days of operation. The microbial composition of Nitrobacter spp. detected by using a Nit3 probe was below 10% in each reactor. In contrast, Nitrospira genus detected with an Ntspa662 probe was around 20%. When CTOs primer was applied in PCR-DGGE analysis to define the nitrifying bacteria, the bands of group B in the R-1 reactor with the highest hydraulic retention time (HRT) had the strongest light intensity compared with two other reactors with lower HRTs after day 64. The bands of the groups were responsible for nitrification with the major dominant population in each reactor depending on the change of ammonia removal rate. These results would directly lead to an understanding of the reactor performance in relation to the ammonia removal, when conventional municipal wastewater treatment plants are retrofitted or upgraded to biological nitrogen removal processes using biofilm.

Adaptation to exploit nitrate in surface soils predisposes yellow-cedar to climate-induced decline while enhancing the survival of western redcedar: A new hypothesis

Yellow-cedar ( Chamaecyparis nootkatensis (D. Don) Spach) and western redcedar ( Thuja plicata Donn), two valuable tree species of Pacific Northwest forests, are competitive in low productivity forests on wet, nearly saturated soils with low nitrogen (N) availability and turnover. We propose a mechanism where cedar trees survive in marginal conditions through exploiting a coupled Ca–NO 3 − nutrient cycle where trees assimilate N as nitrate (NO 3 −), but must accumulate a counter-ion to NO 3 − such as calcium (Ca +2) to control their internal cell pH and provide electrochemical balance. The availability of NO 3 − in cedar forests is favored by increased microbial activity and shifts in microbial community composition that is conducive to N mineralization and nitrification at higher pH. Cedars influence the soils under their canopy by enriching the forest floor with calcium compounds leading to increases in pH. Cedars are also prone to precocious dehardening in the spring when N is released from freeze–thaw events in the soils and conditions appear to favor nitrifying microbial communities. Cedars must concentrate fine-root biomass near the soil surface to access Ca and NO 3 −, but this beneficial physiological adaptation also creates a vulnerability to periodic root freezing injury that is leading to the decline and mortality of at least one of them—yellow-cedar.

Nitrification controls on fluxes and isotopic composition of nitrate from Florida Keys sponges

We performed a combination of field and laboratory experiments designed to investigate sponge-hosted microbial nitrification processes, plus a survey of the prevalence of nitrification among sponge species at patch and outer reefs, Florida Keys, USA. Results from dissolved inorganic nitrogen (DIN) measurements, chemical inhibition, and 15N isotope tracer experiments with Caribbean sponges show that 9 of 12 species tested hosted nitrification. Of the species in our study that are reported to host internal microbial populations, all but one has been found to host this process. Nitrification occurred with an apparent N isotopic fractionation factor of 11±2.6‰ (standard error) and was inhibited by nitrapyrin. Both of these characteristics are consistent with bacterially mediated ammonium oxidation; however, ammonium oxidation by crenarchaeota is also possible. The isotopic composition of nitrate expelled from sponges in situ had lower δ15N values than nitrate from the ambient water column, suggesting active utilization of the nitrate product after it is released. The frequency of the association between nitrifying microbial communities and sponges that harbor large microbial communities suggests that nitrification is an integral part of the metabolic function of many sponge species. Given the abundance of these species on Conch Reef and the magnitude of their nitrification rates, the majority of benthic nitrification on the Florida Keys outer reef tract probably occurs in sponges. Sponge population size and composition could therefore strongly influence the concentration and speciation of DIN in the reef water column, and possibly other ecosystems where sponges are abundant.

Nitrogen Removal via Nitrite from Municipal Wastewater at Low Temperatures using Real-Time Control to Optimize Nitrifying Communities

Although many studies regarding nitrogen removal via nitrite have been carried out, very limited research has been undertaken on nitrogen removal via nitrite at low temperatures. In this study, to improve the nitrogen removal efficiency from municipal wastewater, a pilot-plant of sequencing batch reactor with a working volume of 54 m3 was used to investigate nitrogen removal via nitrite from municipal wastewater at normal and low water temperature. The obtained results showed that high nitrogen removal efficiency with effluent total nitrogen below 3 mg/L could be achieved. Using real-time control with temperature ranging from 11.9 to 26.5 degrees C under normal dissolved oxygen condition (> or =2.5 mg/L), nitrogen removal via nitrite was successfully and stably achieved for a long period (180 days) with average nitrite accumulation rate above 95%. Fluorescence in situ hybridization was carried out to investigate the quantitative changes of nitrifying microbial community in the activated sludge. Fluorescence in situ hybridization results approved that the nitrifying microbial communities were optimized; ammonia oxidizing bacteria became the dominant nitrifying bacteria and nitrite oxidizing bacteria had been washed out of the activated sludge.

Wildfire‐Produced Charcoal Directly Influences Nitrogen Cycling in Ponderosa Pine Forests

Fire is the primary form of disturbance in temperate and boreal forest ecosystems. However, our knowledge of the biochemical mechanisms by which fire stimulates forest N cycling is incomplete. Charcoal is a major byproduct of forest fires and is ubiquitous in soils of most forest ecosystems, yet the biological function of charcoal in soils of forest ecosystems has been greatly overlooked. We conducted a suite of laboratory experiments on soils from ponderosa pine (Pinus ponderosa Laws) forests to determine the influence of charcoal on soil N dynamics and in particular, nitrification. The addition of NH4+ to forest soils had absolutely no effect on nitrification demonstrating that this process is not substrate limited. The amendment of these soils with NH4+ and field collected charcoal (1% w/w) significantly increased the nitrification potential, net nitrification, gross nitrification, and decreased the solution concentrations of plant secondary compounds (phenolics). Charcoal had no effect on nitrification in soils (from a grassland site) that had naturally high rates of nitrifier activity. The increase in gross nitrification in forest soils and lack of effect on grassland soils suggests that charcoal may alleviate factors that otherwise inhibit the activity of the nitrifying microbial community in forest soils. These results reveal the biological importance of charcoal and advance our mechanistic understanding of how fire drives nutrient cycling in temperate and boreal ecosystems.

Fluorescence in situ hybridization analysis of nitrifiers in piggery wastewater treatment reactors

Fluorescence in situ hybridization (FISH) was performed to analyze the nitrifying microbial communities in an activated sludge reactor (ASR) and a fixed biofilm reactor (FBR) for piggery wastewater treatment. Heterotrophic oxidation and nitrification were occurring simultaneously in the ASR and the COD and nitrification efficiencies depend on the loads. In the FBR nitrification efficiency also depends on ammonium load to the reactor and nitrite was accumulated when free ammonia concentration was higher than 0.2 mg NH3-N/L. FISH analysis showed that ammonia-oxidizing bacteria (NSO1225) and denitrifying bacteria (RRP1088) were less abundant than other bacteria (EUB338) in ASR. Further analysis on nitrifying bacteria in the FBR showed that Nitrosomonas species (NSM156) and Nitrospira species (NSR1156) were the dominant ammonia-oxidizing and nitrite-oxidizing bacteria, respectively, in the piggery wastewater nitrification system.

Enrichment of nitrifying microbial communities from shrimp farms and commercial inocula

Nitrifying bacteria were selected from shrimp farm water and sediment ("natural" seed) in Thailand and from commercial seed cultures. The microbial consortia from each source giving the best ammonia removal during batch culture pre-enrichments were used as inocula for two sequencing batch reactors (SBRs). Nitrifiers were cultivated in the SBRs with 100 mg NH4-N/l and artificial wastewater containing 25 ppt salinity. The two SBRs were operated at a 7 d hydraulic retention time (HRT) for 77 d after which the HRT was reduced to 3.5 d. The amounts of ammonia removed from the influent by microorganisms sourced from the natural seed were 85% and 92% for the 7 d HRT and the 3.5 d HRT, respectively. The ammonia removals of microbial consortia from the commercial seed were 71% and 83% for these HRTs respectively. The quantity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was determined in the SBRs using the most probable number (MPN) technique. Both AOB and NOB increased in number over the long-term operation of both SBRs. According to quantitative fluorescence in situ hybridisation (FISH) probing, AOB from the natural seed and commercial seed comprised 21 +/- 2% and 30 +/- 2%, respectively of all bacteria. NOB could not be detected with currently-reported FISH probes, suggesting that novel NOB were enriched from both sources. Taken collectively, the results from this study provide an indication that the nitrifiers from shrimp farm sources are more effective at ammonia removal than those from commercial seed cultures.