While we often think of bacteria as something to be avoided, bacteria are needed in order to support, and recycle life. In particular, bacteria break down dead cells and organisms to recycle the basic elements needed to support life such as carbon, sulfur and nitrogen which are essential to eukaryotes, such as us humans.
Inside our bodies, bacteria live to help us survive. E.Coli, for example lives in our intestines to help us digest food, absorb nutrients, and produce vitamins.
Plants need nitrogen to survive, and bacteria help to transform the nitrogen available in the air into nitrogen useable for the soil. Nitrogen-fixing bacteria are used to convert nitrogen gas into smaller compounds such as nitrates and ammonia. The plant then uses these compounds to make proteins.
The friendly bacteria that live in our bowels are called Probiotics. Two examples of these are Lactobacillus acidophilus and Bifidobacterium bifidum. Benefits of bacteria in the body include improving the immune system, reducing intestinal gas, reducing cholesterol levels, and helping to kill cancer.
Benefits of fungi
The form of fungi mushrooms that are part of our diet are called Agaricus bisporus. Saccharomyces cerevisiae is the type of fungus used for baking bread (yeast) and for making beer. (it is used in medicine to treat diarrhea that is caused by antibiotics)
Other fungi, like bacteria act on dead matter to recycle carbon, the basic element of life. Fungi also produce antibiotics.
One specific benefit of fungi is its usefulness to farmers. Mycorrhizal fungi grows naturally in the earth, and farmers will try to avoid disturbing it in order to allow it to perform its function of protecting the roots from invading bacteria.
Wood of dead trees is broken down by fungi which results in the release of carbon in the atmosphere and nitrogen into the earth. In particular, fungi are able to digest cellulose, which makes up the cell walls of plants.
Trametes versicolor, for example is a fungi which is being used to formulate a new drug. It is being tested as a new cancer treatment.
Probably the best known fungi that is beneficial to humans is Penecillium. This fungus is related to the type of fungi found growing on bread. In medicine, we know it as penicillin, which is used to treat bacterial pneumonia and syphilis. Although some have allergies to penicillin, and resistant bacteria strains are not always stoppable by penicillin, it is still used as an effective antibiotic.