Why are bacteria needed in 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 transporters.

Bacteria are needed in the nitrogen cycle because other living things cannot use atmospheric nitrogen.

As far as nitrogen fixation is concerned, only bacteria are able to fix atmospheric nitrogen into forms usable by other living organisms.

They convert atmospheric nitrogen into chemical forms usable by plants.

Some bacteria fix nitrogen through symbiotic association with the root nodules of leguminous plants while others fix it by non-symbiotic association.

More on nitrogen fixation can be found here: link

a covalent bond, specfically triple bond