Question

What are the nutritional groups of bacteria based on their source of energy and carbon?

Answer 1

Hint: Bacteria require sources of carbon, nitrogen, phosphorus, iron and an enormous number of other molecules. Carbon, nitrogen and water are utilised in noteworthy amounts. The nourishing necessities for bacteria can be grouped according to the carbon source and the energy source.

Complete Answer:
- Microorganisms are grouped as per their energy source and their carbon source. Phototrophs utilise radiant energy (light) as their main energy source.
- Chemotrophs utilise the oxidation and reduction of chemical compounds as their primary energy source.
- Carbon source: On the basis of their source of carbon bacteria can be classified as autotrophs or heterotrophs.
(i) Autotrophs: Carbon dioxide as a carbon source. An autotroph makes organic molecules from inorganic nutrients.
(ii) Heterotrophs: Need organic forms of carbon. A heterotroph cannot make organic molecules from inorganic nutrients.

Further they are classified into:
(I) Photoautotrophs use light as an energy source and carbon dioxide as their primary carbon source. They include photosynthetic bacteria (green sulfur bacteria, purple sulfur bacteria, and cyanobacteria), algae, and green plants. Photoautotrophs transform carbon dioxide and water into carbohydrates and oxygen gas through photosynthesis
(II) Photoheterotrophs utilise light as an energy source but cannot transform carbon dioxide into energy. They utilise organic compounds as a carbon source. They comprise the green nonsulfur bacteria and the purple nonsulfur bacteria.
(III) Chemolithoautotrophs utilise inorganic compounds such as hydrogen sulfide, sulfur, ammonia, nitrites, hydrogen gas, or iron as an energy source and carbon dioxide as their primary carbon source.
(IV) Chemoorganoheterotrophs utilise organic compounds as an energy source and a carbon source.

Note: Some types of bacteria must consume preformed organic molecules to obtain energy, while other bacteria can generate their own energy from inorganic sources.