Embryo protection in contemporary immunology: Why bacteria matter.

Early embryos of many vertebrates and invertebrates develop outside the mother and are exposed to a myriad of potential microbial colonizers. Here we discuss how these embryos are protected from microbial attacks and how they might control and shape their microbiota. In essence we delineate a new role for antimicrobial peptides both in selecting particular bacterial partners during early development and in being important components of a "be prepared" strategy providing transgenerational protection.