what is a microorganism
A microorganism or microbe is an organism which is too small to be seen by the unaided human eye. They are microscopic. The study of microorganisms is called microbiology. Microorganisms include bacteria, fungi, archaea or protists and viruses.The first four types of microorganisms may be either free-living or parasitic. Viruses, however, always reproduce inside other living things.icroorganisms live almost everywhere on earth where there is liquid water, including hot springs on the ocean floor and deep inside rocks within the earth 's crust. Such habitats are lived in by extremophiles. Microorganisms are critical to nutrient recycling in ecosystems, because they act as decomposers.