To survive in hostile environments, cockroaches rely on their own vermin: Blattabacterium, a microbe that hitched a ride inside roaches 140 million years ago, and hasn't left since. "Blattabacterium can produce all of the essential amino acids, various vitamins, and other required compounds from a limited palette of metabolic substrates," write entomologists in a study published Monday in the Proceedings of the National Academy of Sciences.

Researchers have known that cockroaches need the microbes to survive: Kill Blattabacterium with antibiotics, and the insects die. They also knew that roaches store excess nitrogen -- one of life's essential elements, needed to make proteins, amino acids and DNA -- inside their bodies, in tiny deposits of uric acid. But researchers didn't know exactly what became of the uric acid after it was stored, or precisely what Blattabacterium did.

Sequencing the microbe's genome made the links clear. The microbe contains genes that code for enzymes that break down urea and ammonia, the components of uric acid. Other genes instruct the microbe to take the resulting molecules and use them to make amino acids, repair cell walls and membranes, and perform other metabolic tasks.

Blattabacterium also helps free cockroaches from the need to urinate. In humans and other terrestrial animals, otherwise toxic uric acid is diluted with water, then flushed from the body as urine. Cockroaches save that water. Compared to them, the iconic stillsuits worn by the fictional Fremen of Dune would be wasteful.