Animals in a bacterial world, a new imperative for the life sciences
- aDepartment of Medical Microbiology and Immunology, University of Wisconsin, Madison, WI 53706;
- bKewalo Marine Laboratory, University of Hawaii, Honolulu, HI 96813;
- cZoological Institute, Christian-Albrechts-University, D-24098 Kiel, Germany;
- dDepartment of Comparative Biosciences, University of Wisconsin, Madison, WI 53706;
- eRuđer Bošković Institute, HR-10000 Zagreb, Croatia;
- fDepartment of Entomology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853;
- gMax Planck Institute for Marine Microbiology, Symbiosis Group, D-28359 Bremen, Germany;
- hLymphoid Tissue Development Unit, Institut Pasteur, 75724 Paris, France;
- iDepartment of Biology, Stanford University, Stanford, CA 94305;
- jBiotechnology Institute, University of Helsinki, Helsinki 00014, Finland;
- kJulius-von-Sachs Institute, University of Wuerzburg, D-97082 Wuezburg, Germany;
- lMolecular and Cell Biology, University of California, Berkeley, CA 94720;
- mSingapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551, and Centre for Marine Bio-Innovation and School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney 2052, Australia;
- nBotanical Museum, Harvard University, Cambridge, MA 02138;
- oDivision of Biology, California Institute of Technology, Pasadena CA 91125;
- pBiofrontiers Institute, University of Colorado, Boulder CO 80309;
- qDepartment of Earth Sciences, University of Southern California, Los Angeles, CA 90089;
- rDepartment of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
- sCell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599;
- tAmerican Academy of Microbiology, Washington, DC 20036;
- uDepartment of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269;
- vDepartment of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, D-24306 Plön, Germany; and
- wNicholas School and Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708
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Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved January 17, 2013 (received for review December 2, 2012)

Abstract
In the last two decades, the widespread application of genetic and genomic approaches has revealed a bacterial world astonishing in its ubiquity and diversity. This review examines how a growing knowledge of the vast range of animal–bacterial interactions, whether in shared ecosystems or intimate symbioses, is fundamentally altering our understanding of animal biology. Specifically, we highlight recent technological and intellectual advances that have changed our thinking about five questions: 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; how is homeostasis maintained between animals and their symbionts; and how can ecological approaches deepen our understanding of the multiple levels of animal–bacterial interaction. As answers to these fundamental questions emerge, all biologists will be challenged to broaden their appreciation of these interactions and to include investigations of the relationships between and among bacteria and their animal partners as we seek a better understanding of the natural world.
- bacterial roles animal origins
- reciprocal effects animal–bacterial genomics
- bacteria-driven development
- microbiome and host physiology
- nested ecosystems
Footnotes
- ↵1To whom correspondence may be addressed. E-mail: mjmcfallngai{at}wisc.edu or hadfield{at}hawaii.edu.
Author contributions: M.M.-N., M.G.H., T.C.G.B., H.V.C., T.D.-L., A.E.D., N.D., G.E., T.F., S.F.G., U.H., N. King, S.K., A.H.K., N. Kremer, S.K.M., J.L.M., K.N., N.E.P., J.F.R., A.R., E.G.R., M.R., J.G.S., D.T., and J.J.W. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1218525110/-/DCSupplemental.