Microorganisms play an important role in our lives: they help us digest food, break down waste and participate in various life cycles. They are diverse and have adapted to inhabit different environments, including extreme conditions, such as hot springs under the ocean to the polar ice caps; therefore known as extremophiles. There are more microorganisms than cells in us, and the various microorganisms are bacteria, viruses, fungi and protozoa. Many people associate microorganisms with agents that cause death and disease; also often compared to dirt. Although some microorganisms are responsible for causing disease, most of the original hosts of microorganisms are not the human body, so they are not pathogens, but commensals. In this essay, the numerous beneficial microorganisms that carry out processes in biotechnology, agriculture, industries and the environment will be discussed; necessary to sustain life. First we look at the essential uses of microorganisms in the environment, as they play a vital role in many nutrient cycles. For example, the fixation of carbon from the atmosphere during the carbon cycle by autotrophic bacteria, such as cyanobacteria; synthesizes organic molecules for other organisms and releases oxygen for our consumption. Furthermore, microorganisms are vital participants in the food chain as they act as decomposers; breaking down dead organisms and organic materials and releasing minerals for uptake by living organisms and CO2 into the atmosphere for photosynthetic organisms. Microorganisms, known as methanogens, influence the carbon cycle by converting CO2 in their cells into methane and releasing it into the atmosphere; thus increasing methane concentrations as methanotrophs consume methane from the atmosphere, lead… half the paper… eat minerals from ores containing low levels of minerals (Hofkin, 2010). Microorganisms have also brought benefits to humans in the past: the Weil-Felix test for typhoid. A patient infected with Rickettsia will have antibodies against this bacterial species circulating in the blood that can bind to Proteus OX19, a harmless soil bacterium. Doctors used to diagnose typhoid by mixing the patient's blood serum with Proteus OX19, the positive test for typhoid is confirmed when Proteus OX19 is pooled together (Hofkin, 2010). Overall, microorganisms are vital to life on Earth and are more than just pathogens. Few microorganisms are pathogenic, but many more play an important role in various ecological and industrial processes, preserving human health; and every day new discoveries are made that demonstrate that microorganisms are crucial to scientific progress.