Young gut bacteria can extend lifespan—what are they doing that old bacteria don't?

Transplanting microbiota from young to middle-aged killifish extended their lifespan and maintained youthful bacterial communities. The same SCFA-producing bacteria—Faecalibacterium, Bifidobacterium—appear in long-lived mammals from naked mole-rats to centenarians. Is this convergent evolution of gut-immune crosstalk?