They are in us, on us, and nearly everywhere around us. In other words, they are part of our environment and are therefore important to human health. Microorganisms are essential to the web of life in every environment. Microorganisms in the ocean and in fresh water capture energy from sunlight and store it in molecules that other organisms use as food. So we can say that they form essential links in many food chains.
Microorganisms decompose dead organisms and waste material from living organisms.
Bioremediation - a process that uses naturally occurring or genetically engineered microorganisms to transform harmful substances into less toxic or nontoxic compounds. These organisms act as bioremediators by cleaning up oil spills in the ocean. In 1989-the Exon Valdez ran aground in Prince William Sound and 11 million gallons of crude oil leaked out. Scientists sprayed nutrients in hopes of stimulating the growth of native microbes. Microorganisms make nitrogen available to plants.