In the wild, the marine bacterium Zobellia galactanivorans feeds on Porphyra seaweed, which includes the seaweed species used to make sushi wrappers, or nori.

Researchers were studying the microbe to find out which enzymes it uses to break down a carbohydrate abundant in Porphyra seaweed. (Watch explorers navigate the seaweed "forests" off Antarctica.)

When the researchers sequenced the genes for these enzymes, known as glycoside hydrolases, they made an unexpected discovery: The ocean microbe's DNA had already been detected in bacteria living symbiotically in Japanese people.

(Related: "'Bugs' in Our Guts Make Us More Than Human, Study Says.")

The scientists then