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

Step 1: Understanding the ANAMMOX process.
ANAMMOX (Anaerobic Ammonium Oxidation) is a biological process in which ammonium is oxidized using nitrite as an electron acceptor under anaerobic conditions.
Step 2: Nature of microorganisms involved.
The microbes responsible for ANAMMOX are chemoautotrophic bacteria that use inorganic carbon (CO\(_2\)) as their carbon source.
Step 3: Analyzing the options.
(A) Autotrophs: Correct, as ANAMMOX bacteria are autotrophic in nature.
(B) Heterotrophs: Incorrect, they require organic carbon.
(C) Aerobic: Incorrect, ANAMMOX occurs under anaerobic conditions.
(D) Phototrophs: Incorrect, light is not involved.
Step 4: Conclusion.
The ANAMMOX process is dominated by autotrophic microorganisms.

Answer 2

The ANAMMOX reaction converts ammonium and nitrite directly into nitrogen gas without any organic carbon input, so the type of organism involved can be worked out just from what raw materials the process actually uses.

1. Autotrophs: Since the reaction obtains its energy from oxidising ammonium and nitrite, both inorganic nitrogen compounds, and does not require any external organic carbon source, the bacteria carrying it out must fix their own carbon from inorganic carbon dioxide, which is exactly the defining trait of autotrophic (specifically chemolithoautotrophic) organisms.
2. Heterotrophs: These organisms require organic carbon as their energy and carbon source, but the ANAMMOX reaction runs on inorganic nitrogen compounds alone, so heterotrophic metabolism does not fit this pathway.
3. Aerobic: Aerobic organisms need molecular oxygen as the electron acceptor, but ANAMMOX specifically proceeds without oxygen, using nitrite as the electron acceptor instead, so this does not match either.
4. Phototrophs: This pathway takes place in oxygen-free reactors and sediments where light is not a factor, so organisms depending on light energy are not the ones responsible.

Because the ANAMMOX pathway derives energy solely from inorganic nitrogen compounds without organic carbon or light, the organisms carrying it out must be autotrophic in nature.

Therefore, the correct answer is Autotrophs.