Pam Marrone (right), founder and CEO of Marrone Bio Innovations, inspects some colonies of microbes. Marrone has spent most of her professional life prospecting for microbial pesticides and bringing them to market. Dan Charles/NPR hide caption

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Plankton collected in the Pacific Ocean with a 0.1mm mesh net. Seen here is a mix of multicellular organisms — small zooplanktonic animals, larvae and single protists (diatoms, dinoflagellates, radiolarians) — the nearly invisible universe at the bottom of the marine food chain. Christian Sardet/CNRS/Tara Expeditions hide caption

itoggle caption Christian Sardet/CNRS/Tara Expeditions

Mattheos Koffas (left), a biochemical engineer at Rensselaer Polytechnic Institute, and Andrew Jones, a graduate student in his lab, with a flask of microbe-produced antioxidants. Dan Charles/NPR hide caption

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Many artisan cheese producers never pasteurize their milk – it's raw. The milk's natural microbial community is still in there. This microbial festival gives cheese variety and intrigues scientists. iStockphoto hide caption

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The Bronx may be up and the Battery down, but Central Park is where an amazing wealth of different sorts of microbes play. iStockphoto hide caption

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Rugby and meat: a treat for the gut? A study suggests yes. Here Tony Woodcock (left) and Owen Franks of the All Blacks rugby team turn sausages on the barbecue in 2011 in Christchurch, New Zealand. Phil Walter/Getty Images hide caption

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Doctors used a rapid DNA test to identify a Wisconsin teen's unusual infection with Leptospira bacteria (yellow), which are common in the tropics. CDC/Rob Weyant hide caption

itoggle caption CDC/Rob Weyant

Even some euro bank notes may need a good scrubbing. Like dollar bills, these notes are made from cotton and they harbor an array of bacteria. Thomas Leuthard/The Preiser Project/Flickr hide caption

itoggle caption Thomas Leuthard/The Preiser Project/Flickr

Botulism bacteria, or Clostridium botulinum, grow in poorly preserved canned foods, especially meat and fish. The microbe's toxin could be lethal as a bioweapon. Dr. Phil Luton/Science Photo Library/Corbis hide caption

itoggle caption Dr. Phil Luton/Science Photo Library/Corbis

In some human diseases, the wrong mix of bacteria seems to be the trouble. Getty Images hide caption

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Illustration by Benjamin Arthur for NPR