Thisbook examines how the growing knowledge of the huge range of animal-bacterialinteractions, whether in shared ecosystems or intimate symbioses, isfundamentally altering our understanding of animal biology. Individuals fromsimple invertebrates to human are not solitary, homogenous entities but consistof complex communities of many species that likely evolved during a billionyears of coexistence. Defining the individual microbe-host conversations inthese consortia, is a challenging but necessary step on the path tounderstanding the function of the associations as a whole. The hologenometheory of evolution considers the holobiont with its hologenome as a unit ofselection in evolution. This new view may have profound impact on understandinga strictly microbe/symbiont-dependent life style and its evolutionaryconsequences. It may also affect the way how we approach complex environmentaldiseases from corals (coral bleaching) to human (inflammatory bowel diseaseetc). The book is written for scientists as well as medically interestedpersons in the field of immunobiology, microbiology, evolutionary biology,evolutionary medicine and corals.

Thomas Bosch is Professor of General Zoology at Kiel University since 2000. His awards include the Dr. Honoris Cause Degree from St. Petersburg State University, Russia. The Bosch lab studies within others the evolution of immunity, by analyzing the molecular interactions between microbes and host (Hydra) cells that promote normal development and homeostasis.

David Miller is an outstanding world-renowned scientist at the ARC Centre of Excellence for Coral Reef Studies and School of Pharmacy and Molecular Sciences, James Cook University, Australia, where he is heading the program on genomics and metagenomics of coral reefs. The long-term aim of this Program is to understand how the holobiome functions under normal and stressed states.

1. Introduction.- 2. The diversity of animal life.- 3. Origin stories.- 4. Phylosymbiosis from Hydra to man: novel genomic approaches discover the holobiont.- 5. Negotiations between evolving animals and symbionts.- 6. The Hydra holobiont.- 7. Microbes are part of the innate immune system.- 8. Rethinking the origin of immunity.- 9. The coral holobiont.- 10. Are coral reefs doomed?.- 11. Lessons from Hydra and corals.- 12. Hidden impact of viruses.