Floating poop reveals the surprising bacterial partners of whales

Annabel Beichman

Floating poop reveals the surprising bacterial partners of whales

Perhaps the least glamorous way to study whales is to race to where they just surfaced to scoop up their poop. But the floating feces have revealed a surprise about the microbes living in these giant marine mammals' guts. Although baleen whales are carnivores, filter-feeding on fish, krill, and other crustaceans, some of the microbes in their bellies look more like those of a vegetarian, microbiologists reported yesterday in Nature Communications. When this research team isolated and sequenced DNA from humpback and right whale feces, they found the genetic signatures of protein-digesting microbes like those in a lion or a tiger. But they also found quite a few microbes commonly found in cows. Other studies have shown mammals tend to have microbiomes similar to their ancestors’, and whales did descend from the same land animals as cows and hippos. But the researchers think the cowlike microbes may have a functional role, digesting the carbohydrates in whales’ diets, including a complex starch called chitin that makes up the shells and other body parts of crustaceans.  From the gut's perspective, digesting chitin is as big a challenge as cellulose, the tough stuff that cows tackle with multiple stomachs and cud-chewing.