Scientists are discovering, on a daily basis, how useful microorganisms are to ecosystems. As stated in the opening of this unit, bacteria are being used to help clean up oil spills. Bacteria, and other organisms, have also been long known for their important role in decomposing organic matter which returns nutrients to the earth for use by other organisms. Bacteria are also essential in the fixation of nitrogen, converting nitrogen from the atmosphere into ammonia, which is essential to create nucleotides for DNA and amino acids for proteins in living organisms. Anaerobic microorganisms perform putrefaction, the decomposition of animal proteins which is an important role in "trash removal" and "recycling" of organic material (Madigan and Martinko, 6). Recent studies have also discovered a connection between precipitation and the types of protein that certain strains of bacteria produce (Robbins). Also, it is becoming more and more apparent that microorganisms, often referred to as "Probiotics," play an essential role inside of larger organisms such as the human digestive tract and can be used to treat various ailments (Madigan and Martinko, 7).
Oil Oxidizing Microorganisims
Petroleum products can be oxidized aerobically by several varieties of bacteria, molds, and yeasts. These organisms use oil as electron donors, or energy sources, in a process called bioremediation which changes the oil into CO
2
. The activity of these microorganisms is increased at certain temperatures and in the presence of adequate nitrogen and phosphorous which act as fertilizer for the bacteria. If conditions are ideal, bacteria can oxidize up to 80% of the non volatile components of the oil spill (Madigan, and Martinko 651,652).
Decomposers
There are two main groups of microorganisms called chemoorganotrophs and methanogens that decompose the organic carbon of dead organisms into carbon dioxide (CO
2
) and methane (CH
4
). Methanogens use the waste products of the organotrophs, CO
2
and acetate to make methane, they do not break down complex organic matter directly. The CH
4
is then oxidized by organisms called methanotrophs into CO
2.
As shown below in the Carbon Cycle, all carbon biomass eventually returns to the form of CO
2
(Madigan, and Martinko 633).
Microbial Flora in Humans
In humans and other animals, the skin, oral cavity, respiratory tract, intestinal tract and urogenital tract, being exposed to the environment, are nearly always inhabited by microorganisms. These microorganisms perform a variety of processes essential to maintaining health. In human intestines, vitamin B
12
and vitamin K are produced by the metabolic reactions of intestinal flora. Also, in the gut, microbial flora contribute to the absorption of essential steroids (Madigan, and Martinko, 701-710).