Michael G. Hadfield

TL;DR: Recent technological and intellectual advances that have changed thinking about five questions about how have bacteria facilitated the origin and evolution of animals; how do animals and bacteria affect each other’s genomes; how does normal animal development depend on bacterial partners; and how is homeostasis maintained between animals and their symbionts are highlighted.

TL;DR: Research on the tube-dwelling polychaete worm Hydroides elegans is described to exemplify approaches to understanding biofilm bacteria as a source of settlement cues and larvae as bearers of receptors for bacterial cues.

TL;DR: The ability of larvae to respond selectively to inductive surfaces to be retained for at least 3 wk is found, and chemical signals characteristic of early microbial biofilms may indicate freshly available substrata with optimal potential for the growth and survival of H. elegans.

TL;DR: It is shown that a marine bacterium, Pseudoalteromonas luteoviolacea, produces arrays of phage tail–like structures that trigger metamorphosis of H. elegans, providing an entry point to understanding how marine biofilms can trigger animal development.