Animals and microorganisms often establish close ecological relationships. However, much
of our knowledge about animal microbiomes comes from two deeply studied groups:
vertebrates and arthropods. To understand interactions on a broader scale of diversity, we
characterized the bacterial microbiomes of close to 1,000 microscopic marine invertebrates
from 21 phyla, spanning most of the remaining tree of metazoans. Samples were collected
from five temperate and tropical locations covering three marine habitats (sediment, water …