Discuss the evolution of the first living cells and how it affected the amount of each of these gases present in the atmosphere.

The three main uses of bacteria are:

1. Lactobacillus, a genus of Gram-positive helps in converting milk into curd
2. Bacteria are used in brewing and baking and other fermentation processes.
3. Bacteria are also used as pesticides and in composting processes in agriculture, while some species of bacteria play a key role in nitrogen fixation.