An organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide. 

Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates (food) and O2 are the by-products of photosynthesis.

Autotrophic nutrition is generating through the photosynthesis. The necessary conditions required for autotrophic nutrition are following:

1. a) Carbon dioxide (CO2)
2. b) Chlorophyll pigment
3. c) Sunlight

4) Water

Carbohydrates (food) and O2 are the by-products of photosynthesis.

Blue-green algae or cyanobacteria  are an example of nitrogen-fixing bacteria. They have chlorophyll like green plants and they are photosynthetic autotrophs.