U.S. scientific team learns only a few bacteria affect most carbon soil recycling

Twice as much carbon is stored in the soil as stored in vegetation on land, but how it is accumulated and processed by microorganisms is not known. This is an important element for modeling carbon in climate science and soil fertility management.

Now a team of U.S. scientists has devised a method of modeling and measuring the thousands of microbial taxa involved in soil carbon cycling. To their surprise, the data showed that carbon recycling in soil was mostly accomplished by only three to six groups of common bacteria.

The research is published in Nature Communications, June 14.

The team looked at soil from four distinct ecosystems in northern Arizona. To measure the contributions of individual bacterial taxa, they compared soil samples, some natural and others supplemented with glucose or glucose plus nitrogen.

Most types of bacteria are heterotrophs, using organic carbon as food, and the researchers could measure the efficiency of their carbon processing in the laboratory. They used soil samples and quantitative polymerase chain reaction (PCR) to measure the population size and growth of specific taxa with and without additions to the soil.

The researchers found that relative "C [carbon] use in the bacterial community was more consolidated within fewer lineages than the overall distribution of relative abundances might suggest. Averaged across all ecosystems and treatments, 75.7% of bacterial genera used less C than their relative abundance would otherwise predict."

They also identified three bacteria, Bradyrhizobium, the Acidobacteria genus RB41, and Streptomyces, which "together composed 45–57% of carbon flow through bacterial productivity and respiration." 

The article concludes with a call to further research to confirm the group's findings and yield more important information for climate science. 

"With regard to soil respiration modeling, we propose that because the majority of bacterial carbon flux could be accounted for by three to six common genera from ecosystems with different temperature and precipitation regimes, and that these genera were globally abundant and ubiquitous, it is worthwhile to determine both the global ubiquity and consistency in carbon process rates, as well as their determining traits, of such highly abundant bacteria in response to climate change," the team wrote. "Doing so may reveal a core group of the soil microbial community that act as dominant carbon processors."

The team was led by Bram Stone, a postdoctoral researcher at the Center for Ecosystem Science and Society at Northern Arizona University, who currently works at Pacific Northwest National Laboratory. Other scientists in the research team were from Pacific Northwest National Laboratory, Lawrence Livermore National Laboratory, University of Massachusetts-Amherst, and West Virginia University.