Why study population dynamics of microorganisms? First of all, the total number of microorganisms on Earth is estimated to be an incredible 1032 individuals. They inhabit the entire biosphere - from the upper atmosphere to deep beneath the ocean floor, from hot springs to the polar caps. Bacteria alone have more biomass than any other group of organisms on Earth. In fact, roughly half of the global biomass is composed of microorganisms. Just as astonishing as how many of them there are, is what they can do. Microorganisms produce half of the global oxygen. Without them, every food web would collapse, because nutrients and organic substances would no longer be recycled. Microorganisms can grow on the most unlikely diets, such as gasoline. What's more, they can grow fast. The bacterium Escherichia coli, for instance, can double every 20 min. If nothing would stop them, a single E. coli cell could grow into a supercolony the size of the Earth in less than 2 days.
Due to their small size and short generation time, microorganisms are perfect model systems for many universal ecological processes. Microorganisms can be grown in large numbers and studied during many generations, in a simple flask on a laboratory desk. Since population dynamics of microorganisms are governed by the same basic processes as population dynamics of larger species - such as competition, predation, parasitism, and mutualism - microbial model systems are powerful tools for ecological research in general.
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