Novel Metric Examines the Role of Organic Matter and Microbes in Ecological Communities

The Science

Ecological researchers study the relationships among different organisms and between organisms and their surroundings. This makes it critical to understand how individual features in a community, like microbes or types of chemicals, affect the overall community’s development. By examining individual features, researchers can begin to identify those community or assemblage members that drive similarities across communities. To assist in this goal, scientists developed a novel ecological metric, called βNTIfeat. Many microbes do not grow in laboratory conditions. The new metric found that these “unculturable” microbes shape the microbial communities in river corridors. The metric also revealed that organic matter is influenced by a variety of compounds that contain nitrogen and phosphorus.

The Impact

βNTIfeat will help researchers answer longstanding questions about ecosystems. For example, βNTIfeat can help uncover a common group of microbes that significantly affect various river corridors at different local or global scales. This will allow researchers to incorporate the dynamics of these microbes into models. In turn, these models will help scientists to generate predictions about how ecosystems may change due to climate change, wildfires, and other future disturbances.

Summary

Evaluating how ecological communities develop and change is one of the primary goals of ecology. By examining processes that give rise to specific community configurations across varied conditions, researchers will have a better understanding of the fundamental principles that govern community structure and will be able to improve predictions. Unfortunately, comparatively few studies examine the effects that individual features within a community or assemblage play on its overall structure. As part of this study, researchers from Pacific Northwest National Laboratory and California Lutheran University developed a new metric, called βNTIfeat, that investigates the contributions that these features make within a community.

Researchers used βNTIfeat to evaluate feature-level ecological processes in a riverine ecosystem to reveal some key dynamics. First, the team observed that unclassified and unculturable microbial lineages often contribute to differences across the microbial communities; this observation suggests that these unclassified/uncultured lineages play an outsized role relative to their abundance. Secondly, the organic matter assemblages were often driven by nitrogen- and phosphorus-containing molecular formulas, indicating a potential connection to nitrogen/phosphorus-biogeochemical cycles. Finally, by relating the βNTIfeat values for microbes and molecular formulas using a network analysis, researchers determined that members of the microbial family Geobacteraceae often had coordinated contributions to ecological structure with both nitrogen- and phosphorous-containing molecular formulas. This observation suggests there is a complex network of ecological interactions across community types.

Funding

The initial experimental stages of this work were supported by the PREMIS Initiative at the Pacific Northwest National Laboratory (PNNL) with funding from the Laboratory Directed Research and Development Program at PNNL. The later stages of this work (e.g., data analysis, conceptual interpretation manuscript development) were supported by the Department of Energy (DOE) Office of Science, Biological and Environmental Research program, as part of an Early Career Award to James C. Stegen at PNNL. A portion of the research was performed at the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility at PNNL.