The organism that are essential in the conversion of nitrogen-containing compounds to nitrogen forms that are accessible and usable by plants are referred to as nitrogen-fixing bacteria. These bacteria are responsible for converting ammonia to nitrates through fixation.
Chemotrophs get their energy by way of oxidizing inorganic molecules. Heterotrophs consume other plants or animals in order to get energy.
Autotrophs has the ability to make their own food and therefore considered as producers.
Answer - Option 2 - Bacteria