Microbes capable of stunning metabolic feats—such as thriving in extremely hot or acidic conditions —might not require a trek to an exotic hot spring. The neighborhood pond might do just fine.
That’s the implication of a new study in Biology Letters. The researchers find that, far from being confined to extreme environments, organisms that grow in extreme conditions can also grow very well in non-extreme environments, such as freshwater lakes. For those keen to find microbes that could be put to work in settings such as factories, this will be welcome news. “Bioprospecting for industrial relevant organisms with exceptional capacities may thus be done as efficiently in a nearby pond as in exotic extreme locations, such as soda lakes or hot-springs,” says co-author Etienne Low-Decarie, an ecologist and evolutionary biologist at the University of Essex in the United Kingdom.
His group’s findings were born of methodological frustrations. While studying the response of phytoplankton to environmental changes in the lab, Low-Decarie grew dissatisfied with the tools at his disposal. One can only infer so much when studying organisms in a flask, disconnected from their natural environment and biological community, he says. “I was thus looking for better ways to emulate natural conditions, while still allowing us to alter the environmental conditions.”
His lab devised what they call an “amplifying bioreactor,” a vessel (or mesocosm) in which fluid is constantly flowing in and out. The bioreactor received a constant input of organisms from the environment, in this case lake drainage from the watershed of a protected old-growth forest. In this set-up, the authors write, even extremely rare taxa can amplify if they can reproduce in the vessel faster than they are washed out.
With the device in hand, the team imposed ever-larger environmental changes, changes that eventually became extreme. Somewhat to their surprise, they found productive communities of algae and bacteria that could grow in very acidic (pH 2), basic (pH 12), and saline (40 ppt) conditions.
“The vast abundance and diversity of microorganisms living in even a single drop of water do lead to the expectation that at least a few of these organisms are capable of impressive feats,” says Low-Decarie. Even so, he was surprised to see these microorganisms—taken from lake water that’s probably safe to drink—growing in media “that has a pH equivalent to that of household bleach or stomach acid or that is saltier than the ocean.”
It is also surprising, he adds, to find that these organisms have no trouble growing both in these harsh conditions and in the conditions of the lake. Jennifer Martiny, a microbial ecologist at the University of California, Irvine agreed.
“The result that communities, selected for extreme environments, grow just as well under benign conditions is certainly counter-intuitive,” says Jennifer Martiny, a microbial ecologist at the University of California, Irvine, who was not involved in the research. “It shows again how little we know about the organization and distribution of microbial communities. It also demonstrates that microbes offer us many opportunities for clever experiments that we can’t do with larger organisms.”