How to search for microbiomes: the example of bacteria in gallbladder bile.

Questions surrounding the presence or absence of microbiomes in sites of the human body with at most low bacterial biomass in health are still not fully resolved. We begin with the notion of microbiome as "micro-biome," a community of several species, versus microbiota as simply "living things," and return to the pioneer epoch of biome research, which in one sense could be viewed as beginning already around 1800. Applying the biome notion to bacteria in sites of the human body, we find concordance with more recent attempts to test what is and what is not a (core) microbiome in practice. The biome perspective is then applied to a double question that has been addressed, without a consensus answer so far: (1) does the healthy gallbladder typically have a stable microbiota, and (2) do gallbladder microbiota, in either health or (gallstone) disease, qualify as microbiomes in the sense considered here?