Christensenella minuta is a heritable firmicute that is linked to leanness.
By studying 416 pairs of British twins, Julia Goodrich and colleagues from Cornell University have identified the gut microbes whose presence is most strongly affected by our genes. And chief among them was a mysterious bacterium called Christensenella minuta, the one and only member of a family that was discovered just three years ago.
Genetically and physically, it’s rather mundane. It’s yet another rod-shaped, oxygen-hating, nutrient-fermenting bacterium from the Firmicute dynasty—one of the two major groups in our guts. And yet, more than any other microbe, its presence in our body is strongly influenced by our genes. Christensenella also seems to sit at the centre of a large network of microbes; if it’s there, these others are likely to show up too. And it influences our weight: it’s more common in lean people, and it can reduce weight gain in mice.
All of these traits suggest that Christensenella might (emphasis on might) be a keystone species: one that wields a disproportionate influence upon the world around it. The term was first used to describe a starfish, whose absence could entirely change the nature of a seashore. It has since been used to describe sea otters, wolves, and mistletoe. These species might be relatively rare, but they are ecologically powerful. Perhaps Christensenella is similarly important in the world of our guts. And yet, until recently, no one even knew it existed.