But if you got rid of, say, gut bacteria — the microbes that live inside the human digestive system and help keep everything moving — the consequences aren't necessarily dire. Living in a bacteria-free bubble is unnecessary and probably very unpleasant, the scientists argue in PLOS, but not inherently deadly.
Based on studies of bacteria-free animals, it's likely that we'd experience decreased bowel movements (which can lead to a whole host of problems) and a weakened immune system.
Most importantly, you'd have to make sure you stayed germ-free for life. Sudden exposure to life outside the bubble would probably kill you.
Unless, of course, all bacteria disappeared from the planet.
"If someone were to wave an antimicrobial wand and eliminate all bacterial and archaeal life on the planet, what would happen?" Gilbert and Neufeld write. "The usual rhetoric is that life as we know it would end, human societies would collapse, and eukaryotic life would cease to exist. Is all of this true?"
Not exactly, but it wouldn't exactly be a walk in the park.
Humans would carry on as usual, digesting their food and getting sick with viruses, for about a week before we noticed anything was even wrong. But animals that rely on bacteria to digest their food — cows, for example — would then start dying off.
After about a year, all photosynthesis would likely cease. Bacteria are vital in keeping nitrogen cycling through the ecosystem, and nitrogen is vital to plant growth. We'd need to come up with some artificial way of releasing nitrogen from dead organisms and redistributing it, or the planet would slowly starve.
Meanwhile, we'd have a lot of crap to deal with — literally. Without bacteria around to break down biological waste, it would build up. And dead organisms wouldn't return their nutrients back to the system. It's likely, the authors write, that most species would experience a massive drop in population, or even go extinct.
"We predict complete societal collapse only within a year or so, linked to catastrophic failure of the food supply chain," the authors write. "Annihilation of most humans and nonmicroscopic life on the planet would follow a prolonged period of starvation, disease, unrest, civil war, anarchy, and global biogeochemical asphyxiation."
Sounds like a real party.
And all of this would occur much more quickly if all microbes disappeared. We'd get to enjoy life without microbial disease (no more Ebola, malaria, colds, or athlete's foot — yay!) but without fungi to pick up some of the slack of waste-processing bacteria, things would get bad fast.
So no, the planet wouldn't immediately implode given the absence of microbes, these scientists conclude. But it still seems like we should be thanking our lucky stars for the little guys.