It has been known from the inception of microbiology as a discipline in the 19th Century that animals, including humans, bear many microorganisms. Until recently, however, these microorganisms were generally treated as either pathogens or as insignificant: the absence of microbes was equated with health.
This classical understanding of microbes has been called into question with the recent emergence of low-cost, high-throughput gene sequencing techniques that have enabled the study of microbial communities without cultivation. There is now overwhelming evidence that normal development as well as the maintenance of the organism depend on the microorganisms that we harbor. The human is not a unitary entity but a dynamic and interactive community of human cells and microbial cells.
By current estimates, approximately half of the cells in our body are microbial. Interactions with the microbiome are near universal in extant animals and more ancient than the evolutionary origin of animals: our ancestors were multi-organismal before they were multicellular.
Life scientists, including clinicians, are increasingly recognizing the critical importance of the microbiome. Microbiome science is leading to a major re-assessment of biological processes as varied as the physiological function of specific organs, the composition of metabolites in body fluids, and the management of transmissible diseases. As microbiome research matures, broad patterns are
I will propose here that the health of animals, including humans, is fundamental multi-organismal; that any disturbance within the complex community of host and microbial cells has drastic consequences for the wellbeing of the individual member of this association; and that the microbiome should be viewed as an organ of the host. This newfound awareness of the dependency of phenotypes on other species and environmental conditions presents additional layers of complexity for the life sciences including medicine and evolutionary theory; and raises many questions that are being addressed by new research programmes.
About Prof Thomas Bosch
Bosch is a world leader in animal- microbe interactions, and is the Director of a German Science Foundation Collaborative Research Centre “Origin and Function of Metaorganisms” based around Kiel University in north Germany. His particular interests are in the roles of microbes in animal health and the use of simple animal models to understand these interactions. Thomas has published extensively on these subjects, and has authored books for both the popular science (in German) and more general (in English, with Miller) readerships.
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