Bacteria =========================== Specifically a particular type of bacteria that live in nodules on the roots of certain plants (eg the Legume family) called "Nitrogen Fixing Bacteria" . Not other bacteria decompose organic material and release nitrogen back into the atmosphere.
Bacteria can be harmful and give diseases to plants and animals. It can also convert nitrogen to nitrogen compounds. This process makes nitrogen available to plants that is useful to them. Bacteria can also poison the human body with chemicals they produce and release.
Nitrogen fixing is a process whereby certain bacteria convert basic nitrogen to nitrogen compounds that can be absorbed by a plant's root system, for use by the plant. You can compare this to human metabolism; the human body needs iron, but we cannot eat nails or iron bars to accomplish this. We must first convert the iron to compounds that our body can assimilate, digest and absorb.
Because nitrogen is produced by nearly all living organisms, there aren't any activities that don't increase nitrogen in the biosphere. Three examples of these human activities are running, swimming, and walking.
Humans (and most, and if, not all other organisms) need nitrogen is to produce protein. Oxygen is used up in respiration to help produce energy used by the human (and other organisms, but not plants) body.
In the human cell, the mitochondria converts food into usable energy.
Nitrogen is normally not used by the human cell.
The names of three parts of a human cell are the nucleus, mitochondria and ribosomes. The nucleus is the command center of the cell, mitochondria convert energy from food into usable energy and ribosomes create protein.
The human body needs nitrogen for the proper digestion of food and growth. Nitrogen is extremely important in the development of the human fetus.
The human body is about 3% Nitrogen
nitrogen is bad....very bad!