Ask a Caltech Expert: Dianne Newman on Microbes and Climate Change

How can Microbes Help Create a More Sustainable Future?

Microorganisms (i.e., microbes) metabolize an incredible diversity of substances, and these metabolisms can have profound consequences for the environment. For example, microbes can clean up toxic oil spills by literally eating the contaminating oil and turning it into benign byproducts.

Over the course of history, microbial metabolisms have shaped Earth, perhaps best illustrated by the rise of oxygen in our atmosphere. This motivates us to ask: How can we take lessons from this history and predict how microorganisms will contribute to biological and geochemical cycles in the future, as our climate changes?

Answering this question is challenging and requires considering a variety of roles that microorganisms play in different contexts. For example, we must consider:

• How microbial activities in soils and sediments impact the global carbon budget
• How microbial communities help plants get the nutrients they need to grow and how these relationships will change as temperatures rise and soils become more arid or more flooded
• How microbial communities protect plants and animals against pathogens in some cases but fail to do so in others
• How we might alter what we feed cows and other livestock to regulate the methane produced by the microorganisms in their gut

In the marine environment, microbes make similarly important contributions to the cycling of major elements and the health of aquatic organisms, including large California kelp.

Indeed, microbes impact myriad processes in Earth's near-surface environment.

Some of my lab's work focuses on understanding how certain products of bacterial metabolism shape soil microbial communities in such a way as to promote crop growth. Just as the human microbiome—the bacteria that inhabit the gut and other parts of our bodies—helps control many of the factors governing human health, the microbiomes of the rhizosphere—the realm of the soil in the vicinity of plant roots—strongly affect plant health. By affecting the food supply, rhizosphere microbial communities thus make an enormous indirect contribution to human health.

Climate change is expected to result in profound changes to the water cycle, impacting agricultural regions in different ways: increased flooding in certain places and increased desiccation in others. These changes will undoubtably lead to shifts in the composition of rhizosphere microbial communities. We are only at the earliest stages of being able to predict how these communities will respond, much less being able to design strategies to mitigate undesirable changes. Basic research is therefore urgently needed to improve our ability to nurture healthy soil microbiomes and thereby bolster food security.

A predictive understanding of microbial responses to climate-stressors is the first step towards designing interventions that could one day enable more sustainable precision agriculture. For example, plants require phosphate to grow, but this resource comes mostly from mines, which are being depleted. My lab, in collaboration with colleagues at Caltech and elsewhere, is beginning to think about how we might leverage bacteria in the rhizosphere to detect when and where phosphate is needed and help liberate phosphate that is already present but bound up in the soil.

Microbial communities stand to profoundly impact agriculture in a way that could make an outsized contribution to our planet. Whether we will be able to productively harness these communities as the climate changes depends on our ability to understand them in diverse locales and creatively apply our knowledge.

—Dianne K. Newman, Gordon M. Binder/Amgen Professor of Biology and Geobiology

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