Question

Which of the following microbes dominate in ANAMMOX process?

• A. Autotrophs
• B. Heterotrophs
• C. Aerobic
• D. Phototrophs

Hint:

ANAMMOX bacteria reduce energy and carbon requirements by avoiding organic carbon addition.

Answer 1

The Correct Option is A

ANAMMOX bacteria gain their energy by oxidising ammonium using nitrite as the electron acceptor, entirely without oxygen and without any organic carbon feedstock. Since there is no organic carbon available in this reaction system for the bacteria to consume, they cannot be heterotrophic; instead they must build their cell material from inorganic carbon dioxide, which places them firmly in the autotrophic (chemolithoautotrophic) category. The absence of oxygen also rules out an aerobic classification, and the absence of light rules out phototrophy, leaving autotrophic metabolism as the only consistent description of these organisms.

Therefore, the correct answer is Autotrophs.

Answer 2

Working through what each term would require of the ANAMMOX environment makes the answer clear.

1. Autotrophs: Since the ANAMMOX process supplies energy from nitrogen compound oxidation and no organic carbon is present in the system, the responsible bacteria must synthesise their biomass from inorganic carbon, which is the defining feature of autotrophs.
2. Heterotrophs: This classification would require organic carbon to be present as a food source, but the reactors where ANAMMOX occurs are specifically designed around inorganic nitrogen removal, not organic carbon degradation.
3. Aerobic: This term would require dissolved oxygen to be present as the electron acceptor, but ANAMMOX reactors are deliberately kept anaerobic since oxygen would disrupt the reaction.
4. Phototrophs: This would require a light source driving the organisms' metabolism, which is absent in the closed, dark reactor conditions where ANAMMOX is carried out.

Since only the autotrophic description is consistent with the carbon-free, oxygen-free, light-free conditions of the ANAMMOX process, that is the correct classification.

Therefore, the correct answer is Autotrophs.