“Many experts working with microbes share a similar outlook: regardless of how the climate changes, microbes are nearly guaranteed to adapt to survive."
- Ashley Jones, Advocacy Communications Coordinator, American Society for Microbiology
“When people think about viruses, they think about disease. They don’t think about CO2.” - Guillermo Dominguez-Huerta, Scientific Consultant in Microbiology, Ohio State University
On June 23, 1988, NASA director, Dr. James Hansen, delivered a landmark message to the U.S. Congress that underscored the role of human-derived greenhouse gases [GHGs] in global warming thereby resulting in an alarming change in Earth’s climate. Many scientific and public health experts now agree that climate change is the single biggest threat to human health, as well to the health of our planet.
While I am not a climate scientist or expert in the field of climate science, I became acutely aware of the importance of climate change as a health threat about seven years ago when I was asked to give a lecture on the impact of climate change on infectious diseases. My goal in writing this Germ Gems post is to provide the little, actually “microscopic,” picture by considering germs that welcome, and in some cases foster, climate change (”the ugly” and “the bad”), as well as “the good” germs that might help get us out of this mess.
What is climate change? According to the United Nations, “climate change refers to long-term shifts in temperatures and weather patterns. These shifts may be natural, but since the 1800s, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels (like coal, oil, and gas) which produces heat-trapping gases.” I believe many healthcare professionals, like myself, were slow to recognize the problem of climate change because the phenomenon is rooted in the physical sciences (physics and chemistry) rather than the biological sciences.
Amazingly, way back in 1903, a Swedish physical chemist, Svante Arrhenius, was awarded a Nobel Prize for Chemistry for the discovery that changes in carbon dioxide levels in Earth’s atmosphere could substantially alter the surface temperature of the planet through what is called “the greenhouse effect.” I find this fact astonishing because Earth’s atmosphere consists mainly of nitrogen (78%) and oxygen (21%) with only a trace amount of carbon dioxide (0.04%). Arrhenius, however, determined that the properties of carbon dioxide are such that it more efficiently blocks release of heat from Earth into outer space. Methane, another GHG that is found in trivial amounts in the atmosphere, is about 80 times more effective than carbon dioxide in blocking the release of heat from Earth.
Microbes and GHGs. As regular readers of Germ Gems know, bacteria were the first form of life on our planet, emerging about 3.8 billion years ago. Without them and other types of microbes, we wouldn’t even be here to worry about climate change. You may also recall from previous Germ Gem posts that all life forms that require oxygen (called aerobes), including Homo sapiens, can thank cyanobacteria, microbes that first provided this life-sustaining gas in what is called the “Great Oxidation Event,” about 2.2 billion years ago.
But on the dark side, another group of microbes called methanogenic archaea, or methanogens, played a critical role in the global carbon cycle because of their unique ability to produce the potent GHG methane. Mounting evidence suggests that methanogens contributed to climate change that led to three of the “Five Mass Extinctions,” including the one dubbed the “Great Dying” that occurred about 250 million years ago when more than 90% of all life forms became extinct. Germs like methanogens that contribute to climate change-related mass extinctions might be considered “the Ugly.”
Microbes that find climate change invigorating. There are also germs that flourish because of climate change that cause a variety of infectious diseases. We might consider these germs “the Bad.”
Because GHG-driven climate change results in warming and increased moisture, certain insect vectors that carry human pathogens, namely ticks and mosquitoes, are having a field day because their reproductive season and geographic range are extended by climate change.
In my April 21, 2021 Germ Gems post, “How Climate Change Fuels Infectious Diseases,” I discussed several vector-borne infections that are on the rise because of climate change. Most notably for the tick vector that carries Borrelia burgdorferi, Lyme disease is a mounting problem. When it comes to mosquito-borne infections, malaria, dengue, and West Nile virus are promoted most robustly by warmer and wetter conditions.
In addition to vector-borne infections, several water-borne infections are fostered by climate change. Of these, increased cases of cholera and of health problems associated with infestations of blue-green algae are most challenging.
Infections caused by microbes that are transmitted to humans by animals (zoonoses) play a role in a majority of the so-called “emerging infections.” Thus, the warning that climate change is predicted to markedly accelerate zoonotic viral infections through spillovers of viruses from animals to humans is especially worrisome. In their article “Climate change increases cross-species viral transmission risk,” in the April, 2022 issue of Nature, Colin Carlson and his colleagues suggest that by 2070 global warming will drive 4,000 additional viruses to spread between mammals (especially bats) and humans.
As discussed in the March 2, 2022 Germ Gems post, “Extremophiles: Microbes That Love Extremes,” microbes that thrive in extraordinarily challenging environments (called extremophiles), like Arctic permafrost, are known to play a complex role in climate change. Historically, permafrost has been Earth’s largest terrestrial carbon sink, trapping plant and animal material for centuries. Currently, it stores about 1,600 billion tons of carbon. But with rising temperatures, permafrost is fracturing and disappearing, and in the process permafrost is shifting from a carbon sink, which absorbs GHGs, to a “carbon bomb” releasing massive amounts of methane.
Microbial allies that put the brakes on climate change. If you’re looking for the real “pros” in climate change adaptation, hands down you’ll find them in the microbial world. From the very beginning of life on our planet 3.8 billion years ago, microbes have been up against hostile environments as well as up against one another. Evolutionarily, viruses and prokaryotes (bacteria and archaea—single celled microbes without a nucleus), came first, followed by eukaryotes (plants and animals). The theory of evolution evolved considerably in the past century; nonetheless, the concept of “survival of the fittest” still makes sense. The microbial world is composed not only of “fit” pathogens and commensals but also of countless mutualists that contribute in many ways to human wellbeing.
As is reflected in remarks of Arturo Casadevall, M.D., Ph.D., Chair of the Academy of Governors of the American Society of Microbiology, “For a complex problem like climate change, we need to think different. We may need novel approaches, new tools, and unconventional mindsets.” (See, Ashley Jones Robins’ American Society of Microbiology article, “What Microbes Can Teach Us About Adapting to Climate Change,” April 22, 2022.) The really good news is that a growing number of microbiologists and other scientists are developing innovative ways to use microbes to increase carbon sequestration, reduce methane emissions, and produce sustainable biofuels.
For a thorough review of the role of microbes in the health of the ecosystems in soil, oceans, and urban environments, I highly recommend the article, “Microbes and Climate Change: a Research Prospectus for the Future,” in ASM mBio April, 2022. For my part, I strongly believe that increased investment in these “masters of climate change adaptation” is one of the best bets for discovery and development of new technologies for abatement of climate change, before it is too late for our species.
