Many things that we cannot normally see have beneficial affects in our lives. Take for example, bacteria. The metabolic processes and products of bacteria are important in many ways including the manufacture of vinegar and some cheeses, the curing of black tea, coffee, cocoa and vanilla beans, the tanning of leather, and the production of silage. And, bacterial flora inhabiting the intestines of animals often play a part in digestion.

In relation to underground science, certain soil bacteria are important because they help maintain soil fertility which affects crop growth. These include some free living bacteria and some that live in a symbiotic relationship in the roots of certain plants. Their contribution to the enrichment of soil occurs because they help convert a particular gas into a form that is usable by plants. During the process of their normal metabolism they combine the gas with hydrogen to form a simple compound that reacts with substances in the soil to form a different compound. This new compound is used by the plant in the manufacture of complex organic molecules essential to both plant and animal life. The complex organic molecules are amino acids and proteins.