Anmerkung: Intro -- Acknowledgments -- Contents -- 1: Introduction: The Holobiont Imperative -- 1.1 Of Complex Diseases and Animals as Complex Systems: Why Bacteria Matter -- 1.2 The Complexity of Coevolved Animal Communities Was Discovered in 1877 in Kiel, Germany -- 1.3 Looking for a Term for the Functional Entity Formed by a Host and Its Associated Microbial Symbionts -- References -- 2: Major Events in the Evolution of Planet Earth: Some Origin Stories -- 2.1 Microbes Were First: Bacteria Have Existed from Very Early in the History of Life on Earth -- 2.2 Life Did Not Take Over the Globe by Combat, But by Networking -- 2.3 The Transformation of the Biosphere at the Ediacaran-Cambrian Boundary -- 2.4 Our Bacterial Ancestry Is Reflected in Our Genomic Signature -- 2.5 Genomes of Early Emerging Metazoans, Similar to Humans, Contain a Considerable Fraction of Genes Encoding Proteins of Bacterial Origin -- 2.6 The CRISPR/CAS System as Window into Ancient Holobionts -- 2.7 Origins of Complexity: What Makes an Animal? -- 2.8 Multicellularity Requires Cooperation of Cells -- 2.9 Genomes of Early Emerging Metazoans Reveal the Origin of Animal-Specific Genes -- References -- 3: The Diversity of Animal Life: Introduction to Early Emerging Metazoans -- 3.1 How Old Are the "Early Diverging" Animal Phyla? -- 3.2 Cnidarians: The Closest Relatives of "Higher" Animals (Bilateria) -- 3.3 Sponges: One Phylum or More? -- 3.4 The "Comb Jellies": The Enigmatic Phylum Ctenophora -- 3.5 Placozoans: The Simplest Extant Animals? -- 3.6 Eyes, Nervous Systems, and Muscles -- 3.7 The Closest Unicellular Relatives of Extant Animals -- 3.8 The Paucity of Data on Symbioses Involving "Lower" Animals -- References -- 4: Phylosymbiosis: Novel Genomic Approaches Discover the Holobiont -- 4.1 Animal Life and Fitness Is Fundamental Multiorganismal. , 4.2 Phylosymbiosis and Coevolution -- 4.3 Microbiota Diversification Within a Phylogenetic Framework of Hosts: Insights from Hydra -- References -- 5: Negotiations Between Early Evolving Animals and Symbionts -- 5.1 Cnidaria Use a Variety of Molecular Pathways to Elicit Complex Immune Responses -- 5.2 How Do Cnidarians Distinguish Between Friends and Foes: Insights from Corals and Hydra -- 5.3 Selection Can Favor the Establishment of Mutualisms and Animal-Microbe Cooperation -- 5.4 Rethinking the Role of Immunity -- Conclusion -- References -- 6: Role of Symbionts in Evolutionary Processes -- 6.1 Microbes as the Forgotten Organ -- 6.2 Developmental Symbiosis -- 6.3 The Role of Symbionts in Evolutionary Processes -- 6.4 Nematostella, an Early Metazoan Model to Understand Consequences of Host-Microbe Interactions for Rapid Adaptation of a Holobiont to Changing Environmental Conditions -- 6.5 Rapid Adaptation to Changing Environmental Conditions: The Coral Probiotic Hypothesis -- 6.6 The Role of Symbionts in Speciation -- References -- 7: The Hydra Holobiont: A Tale of Several Symbiotic Lineages -- 7.1 Rationale for Studying Host-Microbe Interactions in Hydra -- 7.2 The Hydra Microbiota -- 7.3 Linking Tissue Homeostasis, Development, and the Microbiota -- 7.4 Hydra's Mucus Layer Plays a Key Role in Maintaining the Necessary Spatial Host-Microbial Segregation -- 7.5 Microbes Differ in Embryos and Adult: Embryo Protection -- 7.6 Antimicrobial Peptides Function as Host-Derived Regulators of Microbial Colonization -- 7.7 Symbiotic Interactions Between Hydra and the Unicellular Algae Chlorella -- Conclusion -- References -- 8: Corals -- 8.1 The Case of Reef Building Corals: A Complex Association Between Animal, Algal, and Bacterial Components. , 8.2 Attempts to Generalize About Coral-Microbe Interactions Are Complicated by the Evolutionary and Physiological Diversity of Corals -- 8.3 The Complexity of Coral Microbial Communities -- 8.4 Where Are the Bacteria Located? -- 8.5 Transmission Mode and Ontogeny -- 8.6 Key Components of the Coral Microbiome -- 8.7 Nitrogen-Fixing Bacteria Are Intimately Associated with Corals -- 8.8 Probiotic Microbes and Antimicrobial Peptides -- 8.9 Coral-Bacterial Interactions Modulate Local Climate Via Sulfur Metabolites -- Conclusion -- References -- 9: Bleaching as an Obvious Dysbiosis in Corals -- 9.1 The Complex Relationship Between Stress Sensitivity and the Transmission Mode and Diversity of Symbionts -- 9.2 Do Bacteria Cause Coral Bleaching? -- 9.3 Coral Disease and the Significance of Opportunistic Pathogens -- 9.4 Changes in Coral-Associated Microbial Consortia Under Stress -- 9.5 Symbiodinium as a Recent Intruder on Preexisting Coral-Bacterial Mutualisms -- 9.6 Coda: Are Coral Reefs Doomed? -- 9.6.1 The Geological Perspective: The Persistence of Coral Reefs -- 9.6.2 Impacts of Ocean Acidification on Corals -- 9.6.3 What About the Direct Impact of Thermal Stress or Elevated CO2 on Corals? -- 9.6.4 Can Corals Evolve Fast Enough to Keep Pace with the Rate of Climate Change? -- Conclusion -- References -- 10: The Hidden Impact of Viruses -- 10.1 Beneficial Viruses -- 10.2 Viral Communities in Hydra Are Species Specific and Sensitive to Stress -- 10.3 Bacteriophage Therapy in Corals? -- Conclusion -- References -- 11: Seeking a Holistic View of Early Emerging Metazoans: The Power of Modularity -- 11.1 Animals Are Mobile Ecosystems Carrying a Myriad of Microbes with Them -- 11.2 The Power of Modularity -- References -- Further Reading -- Index.