A "species sorting" experiment finds that microbial communities change under different climate conditions by reactivating dormant species that thrive at different temperatures.
Dormant strains of bacteria that have previously adapted to cope with certain temperatures become active again during climate change, according to a report published in eLife .
The results have important implications for predicting the impact of global warming on ecosystems.
Microbes are integral to ecosystem function, due to their key roles as pathogens, food sources, and in nutrient recycling. To understand the profound impact of climate change on the function of different ecosystems, it is necessary to study the microbial communities within them.
“Microbial communities can respond to warming in the short term through acclimatization (developing unique characteristics that adapt to the environment) or in the long term through adaptation , in which they make evolutionary changes over many generations,” explains the lead author. Thomas Smith, Research Associate at the Georgina Mace Center for the Living Planet, Imperial College London, UK. “But there is also a third mechanism, called species sorting , by which the composition of the overall community, that is, which species are present, is altered with changes in temperature. The importance of species sorting in relation to acclimatization and adaptation has not been previously explored in the context of microbial community responses to temperature changes. ”
To address this, the team carried out a species sorting experiment, where they grew replicated soil bacterial communities collected from a single site at different temperatures ranging from 4°C to 50°C. They then measured the growth and metabolism of each isolated bacterial strain across these different temperatures to determine their thermal performance and studied the genetic sequences of isolated bacteria to see how temperature-responsive traits evolved over time.
They found that evolutionarily and functionally distinct communities emerged under each of the temperature conditions, driven by the resuscitation of microbial strains that had been dormant under previous environmental conditions. This suggests that, rather than new bacteria moving into a community to adapt to new conditions, the original community harbors multiple bacterial strains that are pre-adapted to survive at different temperatures and can switch on when their preferred temperature is reached. As a result, it is likely that microbial communities in nature can respond rapidly to temperature fluctuations.
“Understanding the relative importance of acclimation, adaptation, and species sorting in the assembly and turnover of microbial communities is key to determining how quickly they can respond to changes in temperature. Until now, a mechanistic basis for these community-level responses has not been discerned,” concludes lead author Thomas Bell, Professor of Microbial Ecology at the Georgina Mace Center for the Living Planet, Imperial College London. “We have discovered that resuscitating functional diversity within a microbial community can allow the entire community to survive in response to temperature changes. “Additional studies on other microbial communities, such as those residing in water, will support more accurate predictions of the effects of climate change on different ecosystems.”
