Autotrophic organisms refer to organisms that can use some functions, such as photosynthesis, to convert inorganic substances into organic substances and light energy into chemical energy in organic substances. So autotrophic microorganisms can't use organic matter.

In addition, nitrifying bacteria convert ammonia or ammonium salt into nitric acid through nitrification.

While ammonia and ammonium salts are inorganic substances.

Microorganisms that can absorb organic matter are called decomposers.