Margaret J. McFall-Ngai is Professor of Medical Microbiology and Immunology at the University of Wisconsin School of Medicine. Brian Henderson is Professor of Cell Biology and head of the Cellular Microbiology Research Group in the Division of Microbial Diseases, Eastman Dental Institute, University College London. He is the co-editor of Molecular Chaperones and Cell Signalling (2005), Bacterial Evasion of Host Immune Responses (2003), and Bacterial Disease Mechanisms (2002). Edward G. Ruby is Professor of Medical Microbiology and Immunology at the University of Wisconsin School of Medicine.

'The title of this collection of reviews hints at a refreshing new angle regarding the interplay between a range of hosts and their associated bacterial communities.' Microbiology Today

• Part I. Evolutionary Biology of Animal Host-Bacteria Interactions: 1. How have bacteria contributed to the evolution of multicellular animals? Carol Hickman; 2. The interface of microbiology and immunology: a comparative analysis of the animal kingdom Margaret McFall-Ngai; 3. Co-evolution of bacteria and their hosts: a marriage made in heaven or hell? Jörg Hacker, Ulrich Dobrindt, Michael Steinert, Hilde Merkert and Ute Hentschel; 4. Industrial revolution and microbial evolution Fernando de la Cruz and Julian Davies; 5. Bacteria evolve and function within communities: observations from experimental Pseudomonas populations Paul B. Rainey; Part II. Bacterial Ecology and the Host as an Environment: 6. Coral symbioses: the best and worst of three kingdoms Eugene Rosenberg; 7. Interactions between inherited bacteria and their hosts: the Wolbachia paradigm Zoe L. Veneti, Max Reuter, Horacio Montenegro, Emily A. Hornett, Sylvain Charlat and Gregory D. Hurst; 8. Microbial communities in lepidopteran guts: from models to metagenomics Jo Handelsman, Courtney J. Robinson and Kenneth B. Raffa; 9. Commensal diversity and the immune system: modelling the 'host-as-network' Robert M. Seymour; Part III. Cellular Interactions at the Bacteria-Host Interface: 10. Beneficial intracellular bacteria in the Dryophthoridae: evolutionary and immunological features of a pathogenic-like relationship Abdelaziz Heddi and Caroline Anselme; 11. Regulation of Bordetella-host interactions: mechanisms and evolution Seema Mattoo and Jeff F. Miller; 12. Resident bacteria as inductive signals in mammalian gut development Lora V. Hooper; 13. Virulence or commensalism: lessons from the urinary tract Göran Bergsten, Björn Wullt and Catharina Svanborg; Part IV. Bacterial Interactions with the Immune System: 14. Host responses to bacteria: innate immunity in invertebrates L. Courtney Smith; 15. Bacterial recognition by mammalian cells Clare E. Bryant and Sabine Tötemeyer; 16. Moonlighting in protein hyperspace: shared moonlighting proteins and bacteria-host crosstalk Brian Henderson; 17. Cell signalling pathways as targets for bacterial evasion and immunity Andrew N. Neish; 18. Shaping the bacterial world by human intervention Rino Rappuoli.