I’m talking about the brain in particular. A lot goes on and it consumes a ton of resources.

> A lot goes on and it consumes a ton of resources.

But why should this be taken a sign of a brain microbiome? I fail to see the connection you're implying.

Pure intuition, nothing more. I think we're just beginning to understand the microbiome and the brain does so much, has so many ports, and requires so many resources, that I think there are probably hundreds or thousands of heretofore unknown critters it relies on.