Bacteria which derive energy for food synthesis by oxidizing certain inorganic compounds are said to be

Step 1: Analyze the question The question asks about bacteria that make their own food using energy from oxidizing inorganic compounds (such as ammonia, nitrites, hydrogen sulphide, or iron compounds). It does not ask about bacteria that use light or that feed on other organisms.

Step 2: Concept Organisms obtain food in different ways:

• Autotrophs make their own food from simple inorganic substances. They have two types: • Photosynthetic: the energy source is light (e.g., green plants, cyanobacteria). • Chemosynthetic: the energy source is the oxidation of inorganic compounds (e.g., Nitrosomonas, Nitrobacter, sulphur bacteria, iron bacteria).
• Heterotrophs cannot make their own food and must feed on organic matter. They include parasites and saprophytes.

Step 3: Solution

• Nitrosomonas oxidizes ammonia to nitrite and releases energy.
• Nitrobacter oxidizes nitrite to nitrate and releases energy.
• The energy released is used to build carbohydrates from CO₂ and water. This process is chemosynthesis.

Checking the options:

• A. Chemosynthetic: matches the description.
• B. Heterotrophic: wrong, because these bacteria make their own food.
• C. Parasitic: wrong, because they do not live on a host.
• D. Photosynthetic: wrong, because the energy comes from chemicals, not light.
• E. Saprophytic: wrong, because they do not feed on dead organic matter.

Answer: A. chemosynthetic

Tip: Look at the prefix. "Chemo-" means chemical, "photo-" means light. If the energy comes from chemical reactions with inorganic substances, the answer is chemosynthesis. Also remember that the nitrifying bacteria (Nitrosomonas and Nitrobacter) are the classic examples that come up in JAMB, WASSCE and NECO.