Why are bacteria a necessary part of the nitrogen cycle?
other living things cannot use atmospheric nitrogen.
other living things cannot use the nitrogen in plants.
bacteria are the main nitrogen reservoir.
bacteria are the main nitrogen transpirators.

The correct answer Other living things cannot use atmospheric nitrogen.

Atmospheric nitrogen is present in an inorganic form as N₂, which can not be utilized as such by living organisms like plants.

It must be converted into an organic form so that it can be utilized by plants. This is done by nitrogen fixing Bacteria like Nostoc.

Bacteria fix this atmospheric nitrogen into ammonia, which can be assembled into proteins that can be utilized by plants for its growth.

Thus, bacteria are the significant part of the nitrogen cycle.

the answer is cell division : )