Nitrogen is the main element of protein and enzymes in other words, protein and enzymes cannot be formed without nitrogen. This nitrogen is taken by plants from the soil after fixation. Atmospheric nitrogen fixes by nitrogen fixing bacteria and converts it into nitrates. While human take nitrogen by eating animals and plants.
Two examples include Cyanobacteria streptococci. Prokaryotes don’t really create systems into higher orders of living things so they create chains like the two I mentioned
