Life in a World without Microbes

‘‘Life would not long remain possible in the absence of microbes.’’—Louis Pasteur Or would it? How many times have we started proposals, manuscripts, or presentations with compelling statements about the critical roles that microorganisms play in sustaining life? How often has the possibility of a world without microbes been explored in our introductory microbiology classes? Within the human microbiome research community, entire fields explore the interdependence of humans and their microbial counterparts. But what would happen in a world without microbes? In order to promote discussion about the value of microbial services supporting life on this planet, we explore the opportunities and challenges of a microbe-free existence. Our discussion begins by considering life without the human gut microbiome, follows with a hypothetical scenario of a world without Bacteria and Archaea, and concludes with the implications of a world without all microbes, including microbial eukaryotes and viruses. We do not include the organelles, such as mitochondria and chloroplasts, as microbes in our discussion, simply because most eukaryotic life would cease instantly in their absence. We argue that despite myriad fundamental roles that microorganisms contribute to human and environmental function, it would be false to claim that macroscopic life cannot exist without microbes. However, although life would persist in the absence of microbes, both the quantity and quality of life would be reduced drastically.

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PMID: 25513890