Why are normally unseen members of the food web, such as soil microorganisms, essential to the nitrogen cycle?

Why are normally unseen members of the food web, such as soil microorganisms, essential to the nitrogen cycle? ... Since not all organisms can utilize the nitrogen gas directly, these microorganisms convert nitrogen in different nitrogen compounds, such as ammonia, nitrites, and nitrates. In this article we explore how nitrogen is cycled and the important role of microbes in this cycle. ... Nitrogen is required by all living organisms for the synthesis of organic molecules such as amino acids, nucleic acids and proteins. The Earth's atmosphere contains almost 80% nitrogen gas

Bacteria play a central role:

Nitrogen-fixing bacteria, which convert atmospheric nitrogen to nitrates.

Bacteria of decay, which convert decaying nitrogen waste to ammonia.

Nitrifying bacteria, which convert ammonia to nitrates/nitrites.

Denitrifying bacteria, which convert nitrates to nitrogen gas.

Explanation:

they deliver oxygen to the blood

answer: that would be cheating

explanation: