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Microbial communities forming biofilms and mats represent complex, spatially structured ecosystems where metabolic processes are stratified according to light, oxygen, and nutrient gradients. Biofilms are initial colonization stages, only a few millimeters thick, while mature microbial mats can reach centimeter-scale thickness and display intricate vertical organization. Their structural and functional heterogeneity allows microorganisms to occupy distinct ecological niches within a few...
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Related Experiment Video

Updated: Jun 13, 2026

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors
07:59

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

Published on: December 6, 2018

Temporal variation in maximum cell-specific nitrification rate.

M Fujita1, K Tsuji, A Akashi

  • 1Department of Urban and Civil Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511, Japan. fujita@mx.ibaraki.ac.jp

Water Science and Technology : a Journal of the International Association on Water Pollution Research
|April 15, 2010
PubMed
Summary
This summary is machine-generated.

This study quantified ammonia-oxidising bacteria (AOBs) and Nitrospira in wastewater treatment, finding Nitrosomonas halophila was the sole ammonia oxidizer. Nitrogen load per cell number correlated with nitrification rates.

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Published on: December 20, 2016

Area of Science:

  • Environmental Microbiology
  • Wastewater Treatment Technologies
  • Microbial Ecology

Background:

  • Activated sludge is crucial for wastewater treatment, relying on microbial communities for nutrient removal.
  • Ammonia-oxidising bacteria (AOBs) and Nitrospira are key players in nitrification, a vital step in wastewater treatment.
  • Understanding microbial dynamics and their relationship to treatment efficiency is essential for optimizing wastewater management.

Purpose of the Study:

  • To quantify the cell numbers of ammonia-oxidising bacteria (AOBs), Nitrospira, and Nitrobacter in activated sludge from a thermal power plant.
  • To identify the specific AOB species responsible for ammonia oxidation.
  • To investigate the relationship between microbial cell numbers, nitrification rates, and influent nitrogen loads.

Main Methods:

  • Real-time PCR quantification was used to determine cell numbers of AOBs, Nitrospira, and Nitrobacter over nine months.
  • amoA gene sequencing was employed to identify the dominant AOB species.
  • Aerobic batch tests were conducted to measure maximum nitrification, ammonia-oxidation, and nitrite-oxidation rates.

Main Results:

  • AOB cell numbers ranged from 2.8 x 10^10 to 2.3 x 10^11 cells/L, with Nitrospira at 2.6 x 10^9 to 2.4 x 10^10 cells/L. Nitrobacter were found in minimal quantities.
  • Nitrosomonas halophila was identified as the only AOB species responsible for ammonia oxidation during the study period.
  • While direct correlations between total cell numbers and maximum rates were unclear, cell-specific nitrification rates showed good correlation with influent nitrogen loads per cell.

Conclusions:

  • Nitrosomonas halophila plays a significant role in ammonia oxidation in this specific wastewater treatment system.
  • The amount of nitrogen processed per microbial cell number appears to be a critical factor controlling maximum nitrification rates.
  • This finding suggests that nitrogen loading relative to microbial population size is a key determinant of nitrification efficiency.