ORCC: Do multi-species biofilms accelerate microbial evolution under extreme warming?

To protect society from the hazards of climate change, how quickly climate change will progress and how global regions will be affected needs to be understood. Currently, predictions are hampered by incomplete knowledge about the role of soils in climate change. Soils harbor more carbon than the atmosphere and all global vegetation combined.

As microbes decompose soil carbon, they release CO2—a greenhouse gas—to the atmosphere. Globally, this process produces 10 times as much CO2 each year than fossil fuel burning. How microbes adapt to increasing temperatures is not well-understood and thus, their contribution to the greenhouse effect as temperatures rise is not clear.

Also, microbes reproduce quickly, and it is not clear if they will evolve to produce more or less CO2 as climate change progresses. Few studies have conducted evolution experiments to address this question, and none have evolved microbes in outdoor ecosystems within an intact microbial community. In this research project, certain species of fungi and bacteria will be exposed to extreme warming, either in isolation, or with the natural microbial community, to determine whether microbes evolve better tools, such as biofilms, in a natural microbial community, and whether adaptation results in maintenance or increase in soil carbon decomposition rates under extreme warming, which would potentially accelerate climate change.

Broader impacts include training of undergraduate, graduate, postdoctoral scholars. The PIs will also develop a middle school educational module that includes hands-on activities to learn about microbes and climate change. Middle-school students and teachers from low-income and underrepresented populations will be involved in this project.

In the real world, soil fungi and bacteria will not adapt to climate change in isolation. In fact, fungi and bacteria often interact to form multi-species biofilms. In this project, eco-evolutionary mechanisms of biofilm formation in response to extreme warming will be examined and how this will impact large-scale organic C decomposition will be studied.

This research will thus provide a deeper understanding of how soil microbes adapt to climate change, and, thus, improve predictions under future climate scenarios. The PIs hypothesize that fungi and bacteria will adapt to extreme warming more effectively if they interact with one another. Specifically, extreme warming will select for biofilm formation because extracellular polymeric substances (EPS) of biofilms can buffer microbes from heat damage.

In addition, adaptation to extreme warming within multi-species biofilms will result in faster organic C decomposition since EPS can improve the longevity and efficiency of organic C-degrading enzymes in the environment. Thousands of generations of bacterial and fungal strains will be exposed to extreme warming in the field while manipulating their interactions with the whole microbial community and controlling their ability to form multi-species biofilms.

To focus on mechanisms underlying adaptation, computer-based ecosystem modeling and lab studies with the same experimental design as the field will be performed. In each case, growth rate, survivorship, biofilm formation, and organic C decomposition under extreme warming will be monitored. This project will also assess EPS production in soil samples from NEON sites which represent many different terrestrial habitats with a wide range of environmental conditions, thus broadening the generalizability of the research.

This award was co-funded by Integrative Organismal Systems and the Division of Environmental Biology in the Directorate for Biological Sciences.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.