Despite their minuscule size, microorganisms — including, bacteria, viruses and algae — are among the most prolific environmental regulators on the planet. These tiny, single-celled species wield the ability to alter the Earth’s climate, spread human disease, regulate the metabolism of animals and some serve as the building block of the aquatic food chain. In the Great Lakes — which provide drinking water for 48 million people and support a $7 billion recreational fishery — researchers know next to nothing about some of the most abundant microbes.