Soil Studies Provide Big Benefits

When it comes to studying microbial communities in soil, the smaller the sample, the better. Only by approaching the scale at which microbes interact and function, the micron scale, can scientists understand how the community works. To that end, scientists at Pacific Northwest National Laboratory assayed sub-millimeter-sized soil aggregates to determine biomass and enzyme potential.

They found that across all enzymes, the smallest macroaggregates had the greatest activity.
 
Also, the range of enzyme activities observed in all macroaggregates supports their hypothesis that functional potential in soil is not uniform across aggregates, and that both "hot spots" and "cold spots" of activity are measureable; that is, the function they measured was distributed in a patchy fashion. The work is described in the journal Soil Biology and Biochemistry.
 
The scientists adapted four enzyme assays to single aggregates of soil so they could study habitat-relevant units. This has also enabled them to describe variability in the enzyme potential at the individual macroaggregate level. Measuring the potential activity of an enzyme in soil provides information about the soil's ability to mediate critical reactions such as those associated with decomposition and other ecosystem functions. These ecosystem functions contribute to the soil's resistance and resilience to environmental changes.
 
Traditionally, soil microbiologists study microbial communities and processes in batch scale; that is several to hundreds of grams. Studying function at the aggregate scale, which is closer to that of microbial habitats, presents greater opportunity to link microbial community structure to function and may reveal more information about soil as a habitat for microbial communities
 
In turn, increased understanding of microbial interactions in soil opens up myriad possibilities for land management. If scientists can learn how bacteria live and function together, the knowledge can lead to new opportunities for mitigating climate change and greenhouse gas emission or in bioremediation.

Scaling is the key.

"Studying soils at the batch scale doesn't show us a microbial community," said PNNL microbiologist Dr. Vanessa Bailey. "The larger the sample, the larger the volume throughout which the microbes are distributed. And as distance between microbes increases, the likelihood of interaction decreases.
 
"Processes mediated by microbes occur at the micron scale," continued Bailey. "An aggregate that's less than 1 millimeter in diameter, or slightly thinner than a credit card, gets us to where the microbes within are more likely an interacting community rather than a collection of organisms in a single sample."
 
To assess the functional potential at the macroaggregate scale, which ranges from 250 -1000 micrometers in diameter, the scientists developed a way to assay biomass and enzymes in individual soil macroaggregates. They took ten adjacent soil cores from grassland at the U.S. Department of Agriculture Conservation Field, near Pullman, Wash. They used a sieve to select individual macroaggregates in three size classes: 250-425, 425-841, and 841-1000 micrometers, respectively.
 
They then measured microbial activity using β-glucosidase enzyme assays and microbial biomass using adenosine triphosphate, or ATP, to link biomass to cellulolytic potential. β-glucosidase is likely the rate-limiting step in cellulose degradation. Its presence is "patchy" at the small scale, meaning that microsite controls may exist that control its production and/or stabilization. Those microsite controls may include the competence of the intrinsic microbial community.
 
"We hope to eventually link community structure with function in a complex natural ecosystem such as soil," said Bailey. "And from that, we could have the potential to determine if there are biological rules that are constant within these microsites that will help us understand the variability of phenomena in the landscape."

Download Center

  • Monitoring and Reporting on Air Emissions for Regulators and the Real World

    When it comes to managing compliance and regulatory issues surrounding air emissions, there are no easy jobs. With interviews from practitioners from American Electric Power, Red Cedar Gathering, Trinity Consultants, and Cority, this eBook provides practical advice to advance your air emissions monitoring and reporting programs.

  • What Every EHS Professional Should Know About ESG

    Join experts from Arcadis and Cority on April 27th to learn the most common ESG reporting frameworks and how technology can help you improve reporting efficiency, identify areas for improvement, and create defensible audit trails.

  • Green Quadrant EHS Software 2021

    Read the new report by independent analyst firm, Verdantix, to get an unbiased comparison of the 22 most prominent EHS software vendors in the industry.

  • RFP Template for Waste Management Software

    Learn the essential questions to ask when evaluating waste management software solutions with this free, ready-to-use RFP template

  • 5 Keys to Best-in-Class Chemical Management

    Running a safe chemical program is challenging and complex: from knowing what's on-site to proper handling and disposal - all while navigating regulatory changes. Learn the best ways to mitigate chemical risk, get the most value out of your data, and gain buy-in for a chemical management solution.

Featured Webinar