Pathogens are only a small percentage of all prokaryotes. In fact, prokaryotes provide essential services to humans and other organisms. Nitrogen, which is not usable by eukaryotes in its plentiful atmospheric form, can be “fixed,” or converted into ammonia (NH3) either biologically or abiotically. Biological nitrogen fixation (BNF) is exclusively carried out by prokaryotes, and constitutes the second most important biological process on Earth. Although some terrestrial nitrogen is fixed by free-living bacteria, most BNF comes from the symbiotic interaction between soil rhizobia and the roots of legume plants.
Human life is only possible due to the action of microbes, both those in the environment and those species that call us home. Internally, they help us digest our food, produce vital nutrients for us, protect us from pathogenic microbes, and help train our immune systems to function properly.
Microbial bioremediation is the use of microbial metabolism to remove pollutants. Bioremediation has been used to remove agricultural chemicals that leach from soil into groundwater and the subsurface. Toxic metals and oxides, such as selenium and arsenic compounds, can also be removed by bioremediation. Probably one of the most useful and interesting examples of the use of prokaryotes for bioremediation purposes is the cleanup of oil spills.