[Recent discovery in nitrification: One-step nitrification and complete ammonia oxidizing microorganisms]

Area of Science:

• Microbiology
• Environmental Science
• Biogeochemistry

Background:

• Nitrification is traditionally understood as a two-step process involving ammonia oxidizers (AOB/AOA) and nitrite oxidizers (NOB).
• Kinetic theory suggested the possibility of a one-step nitrification process mediated by a single microorganism, but direct evidence was lacking for over a century.

Purpose of the Study:

• To provide an overview of the discovery of one-step nitrification.
• To highlight the identification and significance of complete ammonia oxidizing microorganisms (Comammox).

Main Methods:

• Review of scientific literature and research findings leading to the discovery of Comammox.
• Identification of cultivated and uncultivated bacteria capable of complete ammonia oxidation.

Main Results:

• The discovery of four Comammox bacteria (three cultivated, one uncultivated) capable of oxidizing ammonia directly to nitrate.
• Confirmation of one-step nitrification, challenging the established two-step model.

Conclusions:

• The discovery of Comammox and one-step nitrification has overturned a long-standing scientific dogma.
• This finding necessitates further research into the ecological roles and contributions of Comammox in the global nitrogen cycle.