LIFE CYCLE TRIGGERS. “Perhaps the most pervasive example of microbial signaling in animal development is the induction of settlement and metamorphosis of many marine invertebrate larvae. This transition is an absolute requirement for completion of the animal’s life cycle and is contingent on induction by exogenous morphogenetic cues, many of which are produced by bacteria associated with a particular environmental surface.”
http://www.pnas.org/content/110/9/3229.full