Microbes: The Secret Architects of Animal Development and Behavior You Never Knew About

What if the blueprint for animal development and behavior isn’t written solely in animal genes but also in the genomes of their microbial partners? Recent research reveals that microbes are not passive inhabitants but active architects influencing how animals grow, defend themselves, and interact socially.

The Hawaiian bobtail squid’s remarkable ability to glow and avoid predators depends on Vibrio fischeri bacteria. These microbes colonize a specialized light organ, triggering its maturation and enabling the squid’s camouflage. Without these bacteria, the organ fails to develop properly.

Similarly, choanoflagellates—single-celled relatives of animals—form multicellular colonies only when exposed to specific bacterial molecules. This suggests microbes may have played a role in the evolutionary leap to multicellularity.

Microbes also educate the immune system. Animals raised in sterile environments show underdeveloped immune organs and heightened susceptibility to infections. Certain bacterial molecules suppress inflammation and promote immune tolerance, maintaining health.

Beyond development and immunity, microbes influence animal behavior through chemical signaling. Bacteria in scent glands produce odors used by animals like hyenas to communicate clan membership and reproductive status. Humans’ unique body odors are also shaped by skin microbiota, affecting social interactions.

These discoveries reveal a profound interconnectedness: animals evolved in constant dialogue with microbes, shaping biology and behavior. This challenges the traditional view of animals as autonomous beings and opens new avenues for medicine and ecology that embrace our microbial partners.

Understanding these microbial influences enriches our appreciation of life’s complexity and offers hope for novel therapies and conservation strategies.