Nitrospira community composition in nitrifying reactors operated with two different dissolved oxygen levels

Area of Science:

• Microbiology
• Environmental Science
• Biotechnology

Background:

• Nitrospira are dominant nitrite-oxidizing bacteria (NOB) crucial for nitrogen cycling in aquatic environments and wastewater treatment.
• Nitrifying bioreactors rely on NOB for efficient ammonia oxidation.
• Understanding Nitrospira community dynamics is vital for optimizing bioreactor performance.

Purpose of the Study:

• To investigate the effect of varying dissolved oxygen (DO) concentrations on Nitrospira community composition in nitrifying bioreactors.
• To determine if DO levels influence the phylogenetic structure of Nitrospira populations over time.

Main Methods:

• Two nitrifying bioreactors were operated under high and low dissolved oxygen conditions for 300 days.
• Phylogenetic analysis using 16S rRNA gene sequences was performed.
• Terminal Restriction Fragment Length Polymorphism (T-RFLP) was employed to assess microbial community composition.

Main Results:

• Initially, Nitrospira communities in both reactors were similar, primarily belonging to group 1.
• In the high-DO reactor, approximately half of the Nitrospira community shifted to group 2 after 179 days.
• No significant community shift was observed in the low-DO reactor.

Conclusions:

• Dissolved oxygen is a critical environmental factor shaping Nitrospira community structure in nitrifying bioreactors.
• High DO concentrations can drive significant shifts in Nitrospira populations, potentially impacting nitrification efficiency.
• Further research can explore the specific mechanisms by which DO influences Nitrospira group dynamics.