Why Dormant Microbes Matter in a Changing Climate
Yet, for all their hanging out, dormant microbes are critical for shaping how microbial populations survive, evolve and respond to ever-fluctuating environments, a role increasingly pertinent against the stark backdrop of climate change. Researchers are digging into the dynamics of microbial dormancy to get a better handle on what it means for the future of life on Earth—and how we can harness it to make that future a brighter one.
Defining Dormancy: Easier Said Than Done
To capitalize on dormancy, researchers must first wrestle with a deceptively difficult question: ?
Most people have a general idea about what dormancy means, with hibernating bears or plant seeds coming to mind. These examples—and countless others spanning the tree of life—align with many definitions of dormancy: a reversible state of reduced metabolic activity, in which an organism retains viability in less-than-ideal environmental conditions. Notably, “when a cell is dormant, it can't reproduce, so it can't divide and grow its population size,” said Ashley Shade, Ph.D., Director of Research at the French National Center for Scientific Research. “You have this interesting trade-off of protection versus reproduction.”
In microbes, various phenotypes are stamped with the dormancy moniker. Yet, the nitty gritty of what microbial dormancy means varies across sub-fields, as different scientists apply the idea to the organisms and questions driving their research. As an example, Shade, who will be convening a at ASM Microbe 2025, highlighted that clinical microbiologists often equate dormancy with persisters (cells that survive antibiotic exposure without antibiotic resistance genes/mutations, presumably by ).
Environmental microbiologists, however, see dormancy a little differently. “We think about it as a very common state of microbial existence in the world, because the environment is harsh, and conditions are fluctuating a lot,” Shade said. That is, it’s less about a single phenotype, and more about a general strategy for persistence.
The tricky part about dormancy—and coming to a consensus about what it means—is that measuring it is hard. There are a lot of ways to determine if a cell is active or inactive, and depending on the measurement method used, the conclusion may differ from 1 study to the next. What’s more, there are only a few cases where one can definitively say, “that microbe is dormant” (e.g., bacterial spores, which are tough, non-reproductive structures that differ considerably from an active cell). For most cells, dormancy is more subtle and involves behaviors like reducing cell volume or modifying the cell membrane. “In actuality, this is a gradient,” Shade said. “It's not like you're dormant or not. It's like you're really active, you're doubling, you're replicating, or you're less active.”
Jay Lennon, Ph.D., a professor of biology at Indiana University Bloomington, agreed. “There’s no single right way to achieve dormancy,” he said. “Different microbes (or other taxa) are going to engage in dormancy in different ways. Scientists can come up with different names for them, but it’s still dormancy in the end, the same way that beetles, bats and birds all ‘fly.’” According to Lennon, getting lost in the weeds of semantics overlooks that dormancy is a broad “biological theme” that has evolved independently in wildly diverse organisms. The key is to create a working definition that captures this theme but leaves breathing room to acknowledge the nuance associated with each organism. The more scientists can do this, the easier it is to build a shared conceptual framework to make sense of complex biological systems.
For , a principal investigator at Newcastle University Biosciences, it is this ideological push-and-pull itself that gives rise to new understanding. “Science is about lack of consensus,” he said. “We constantly challenge our assumptions.” Old concepts and definitions are routinely revisited and revised as new knowledge surfaces. What doesn’t change is the importance of engaging in the dormancy debate. “I think it is very important, because ‘what is dormancy?’ is related to the question ‘what is life?’”
Dormancy Impacts Microbial Evolution and Community Function
While the conceptual and semantic underpinnings of dormancy may change, its significance in the microbial world is undebatable. “We tend to think about life as a form of motion,” Melnikov said. And yet, paradoxically, “the primary activity of many biological systems is to do nothing.”
Scientists estimate that at a given time. The concentration of bacterial endospores in marine sediment alone suggests they make up at least 10% of the global microbial biosphere (this doesn't account for the other modes of microbial dormancy that exist, which means the actual percentage could be might higher). In other words: dormancy dominates.
One can think of a collection of dormant microbes in a given environment as forming a , “which is just the sum, or the reservoir of all dormant individuals,” Lennon explained. The seed bank preserves population information, diversity and, ultimately, longevity in hostile environments. Because of their reduced metabolic prowess, dormant microbes have critical ramifications for the function and evolutionary trajectory of microbial populations.
For example, genetic mutations—often associated with copying errors in DNA during cellular division—are the fodder of natural selection. “However, if you have a large seed bank and many organisms aren't dividing, then the input of new mutations is going to be reduced. So that should have consequences for evolution,” Lennon said. On the flip side, when dormant cells resuscitate (i.e., resume the business of growth and reproduction), they contribute to the genetic variation of a population, which may speed up rates of adaptive evolution.
Dormancy impacts microbes in other ways, too, including shaping how they with one another. Pathogens can leverage dormancy to survive within a host, as well as in the presence of antimicrobials, making infection treatment a challenge. Moreover, like plant seeds passively moving between environments via the wind or in the poop of a critter, dormancy may allow microbes to disperse to new places. In such cases, if a microbe resuscitates and proliferates in a novel environment, the resulting population could influence the form and function of the existing microbial community, and how that community interacts with the broader ecosystem.
The Climate is A-Changin'
“The thing about inactive microbes, or low-activity microbes, is that they're not contributing very much to functions, or may not be contributing at all depending on how inactive [they are] at the moment,” Shade said. “And so, as the climate changes, or as stressors are imposed on our environment, you might expect that some microbes that are thriving might go inactive, or even go extinct in response to those stressors, and other ones might wake up. We really don't know for a lot of situations how the microbes will either activate or inactivate in response to climate change stressors, and that is going to directly impact the functions that are provided by the microbial communities in those environments.”
that the ability of soil bacteria to cope with dramatic temperature changes (including those never seen before in their native environment) is largely dependent on dormant microbes. They are also key in (a region especially impacted by climate change). Moreover, Shade’s lab found that drought stress causes , suggesting there are members of the rhizosphere that kick into gear when exposed to certain stressors.
“I have no judgment whether those are good guys or bad guys as far as their association with the plant or what they might provide,” she noted. “But we do know to expect some shifts,” which could impact issues like crop production and health. Indeed, some resuscitated microbes may have functions that overlap with those that go dormant (or extinct), essentially compensating for functions that were lost, or they may have entirely new functions whose impacts will only become clear over time.
Harnessing Microbial Dormancy
What is clear now is that the more scientists delve deeper into the questions surrounding microbial dormancy, the more they can generate strategies to leverage dormant microbes in beneficial and sustainable ways. According to Shade, this could involve developing methods for with functions that support planetary health. Lennon pointed to possibilities in material science, highlighting that some scientists are integrating bacterial spores into plastic; when the spores germinate, they degrade the plastic—a potential solution to the world’s big plastic problem.
Part of capitalizing on microbial dormancy involves delineating the diverse mechanisms that make it possible; this recognition forms the basis of Melnikov’s research. His lab is interested in a slew of proteins known as . Found in bacteria, animal and plant cells alike, these proteins bind essential cellular machinery, such as ribosomes and RNA polymerase, and keep them in a state of stasis—they put the brakes on while shielding essential enzymes from degradation. In this way, hibernation factors are an essential part of the “ability of organisms to put life on pause, so to speak,” said Melnikov, who will present his work on the molecular structure of dormant bacterial cells at ASM Microbe 2025.
The kicker? “When we know how these factors work—what activates them, what inactivates them—we gain the ability to either induce dormancy or prevent [microbes] from entering dormancy.” For example, many hibernation factors occupy ribosomal drug-binding sites used by some antibiotics, triggering protein-drug competition. “This means that the very same drugs that we currently use to suppress microbial growth [under] growth-favorable conditions to induce irreversible transition of organisms to dormancy in growth-unfavorable conditions,” Melnikov explained.
This is just the tip of the iceberg when it comes to understanding—and exploiting—the molecular basis of dormancy. Ultimately, for not doing much, dormant microbes are becoming an increasingly captivating area of study.
“[Dormancy] is a key part of what makes microbes able to colonize, proliferate [and] persist in so many harsh situations,” Shade said. “It's not been completely ignored, but [it has been] under-explored. There are so many things about the biology and ecology of dormancy that we can learn, and I'm excited for that next chapter of research in this field.”
Whether your research deals with microbial dormancy or any number of other topics spanning the microbial sciences, ASM Microbe is the place to present and learn about cutting-edge research in your field. Not sure where to begin?
