Porphyran, a polysaccharide present in the cell walls of a red algae that is used notably in the preparation of sushi, is broken down specifically by an enzyme called porphyranase. This new enzymatic activity has been identified in marine bacteria and, surprisingly, in the bacteria that populate the gut of the Japanese. Scientists have explained this discovery by a transfer of genes between the bacteria, that allows the gut microbiota of the Japanese to acquire all the "machinery" it needs to consume the algae that surround sushi.