Life without microorganisms would probably be hell – a new study published in PLOS Biology entertains the idea and explains the repercussions. The aim was to “promote discussion about the value of microbial services supporting life on this planet”. Scientists Jack Gilbert and Josh Neufeld set out to explore the possibilities in a microbe-free world, and concluded that humans would ultimately die out.
Louis Pasteur once said that “life would not long remain possible in the absence of microbes”. Indeed, we cannot deny the critical role they play in our lives and ecosystems. The intimate interactions that have been developed between humans and bacteria in the alimentary canal are, for instance, testimony to their great importance. But, how right was Louis Pasteur though?
To test their hypotheses, the researchers starting with the human gut microbiome. In their scenario, they first got rid of the latter, and eventually of all microorganisms in the world altogether. That would include bacteria, archaea, viruses, fungi, protists, and algae.
The absence of gut bacteria would impact negatively on digestion. Most issues pertaining to the nutritional consequences can, however, be countered by taking in dietary components synthesised chemically. But, the other side of the coin cannot be ignored: no gut bacteria would lead to weaker immune systems. As a result, a gnotobiotic condition – a germ-free one – would require one to permanently live in a bubble to provide protection against pathogens. Depriving the world of all bacterial and archaeal life would perhaps solve this problem. But then, global photosynthesis would gradually stop because bacteria are essential for nitrogen-fixing for the growth of plants. Consequently, carbon dioxide would accumulate in our atmosphere. Cattle would die out. Waste would build up.
“Even though our dairy industries, cattle farmers, biotechnology companies, food producers, hospitals, and wastewater treatment systems would begin making headlines within a day or two, it would take us nearly a week to realize what had happened,” the authors write. “Annihilation of most humans and non-microscopic life on the planet would follow a prolonged period of starvation, disease, unrest, civil war, anarchy, and global biogeochemical asphyxiation.”
Louis Pasteur was probably right, you know: according to the authors, humans and insects might persist in small groups, but long-term survival is uncertain.
Notice also that with no microorganism to decompose materials that need to be decomposed, the planet would quickly become a land covered in waste – our own waste included, and ultimately, us as part of the waste as well.
“Their roles are not necessarily irreproducible,” the authors conclude. “When you next hear someone claim that we cannot live without microorganisms, it would be appropriate to ask them to qualify the statement. Would we still be able to eat and digest food? Yes. Would life be extinguished in the absence of bacteria and archaea or in a world without any microbes? Not immediately, not all life, and potentially not for a long time.”