Microoganisms that convert various nitrogenous compounds into ammonia is

Answer: Option A

Microoganisms that convert various nitrogenous compounds into ammonia are Actinomycetes.
The Actinomycetales is an order of Actinomycetota. A member of the order is often called an actinomycete. These are generally gram-positive and anaerobic and have mycelia in a filamentous and branching growth pattern.
They form symbiotic nitrogen-fixing associations with over 200 species of plants, and can also serve as growth promoting or biocontrol agents, or cause disease in some species of plants.