MIM: Microbial Division of Labor in Polysaccharide-Degrading Communities

Purdue University, West Lafayette IN

Investigators

Abstract

Microbial ecosystems called ‘microbiomes’ colonize all environments on Earth. Microbiomes play crucial roles in important environmental processes such as nutrient cycling and stress resistance. In these ecosystems, microbes compete strongly for easy-to-consume simple foods like sugars, which are rapidly consumed. Therefore, microbial communities in nature typically survive on more complex food sources like polysaccharides. In competition for a simple sugar molecule, one microbe will eventually win and the losers will go extinct. In contrast to simple sugars, polysaccharides typically require many different enzymes for complete degradation because of their complex structure. This provides opportunity for microbes to divide the labor of degradation amongst themselves with each microorganism specializing in a few tasks. Thus, microbial degradation of polysaccharides can allow diverse species to coexist. The goal of this project is to uncover the rules of life that govern how microbes divide labor when degrading complex polysaccharide molecules. To do so, the role each microorganism plays in polysaccharide degradation will be measured in natural and synthetic microbial communities. A computational model will be developed and used to predict how members divide labor. Further experiments will test these model predictions for validation. Successful completion of this research will yield new understanding of the rules by which division of labor sustains microbial diversity. Such information will have broad benefits by facilitating the engineering of microbial bioprocesses and controlling natural microbiomes. In addition, this project will help develop the next generation microbiome workforce by providing training in advanced techniques for measurement and modeling of microbial behavior. Further benefits to society will arise from public outreach designed to boost awareness of microbial ecology and teach microbial ecology concepts to K-12 students. The goal of this project is to uncover the ecological rules governing how complex substrate structure influences microbial diversity and community function through division of labor (DOL). This project tests the hypothesis that polysaccharide substrate molecular complexity sustains functionally degenerate microbial diversity through diverse transport strategies and alternate gene regulatory patterns. Together, diversity and gene regulation result in distinct hierarchies of preferred polysaccharide structures and degradation products. These mechanisms are further hypothesized to result in DOL among members that allows niche partitioning of microorganisms that degrade specific molecular structures, thereby minimizing competition. Specific research objectives to achieve the project goals are to: i) define the niches of polysaccharide-degrading microbial communities and the overall impact on community productivity and C and N flow; ii) develop genome-scale metabolic network models of polysaccharide-degrading communities and propose a theoretical framework that decomposes microbial interactions into basic DOL units; and iii) determine how DOL plays a key role in linking diversity to community productivity and stability. Successful completion of this research will uncover mechanisms by which microbes divide labor in communities consuming complex substrates and translate that mechanistic knowledge into theory that describes how microbial DOL interactions maintain diversity and influence emergent properties. Broader benefits to society result from advancing synthetic ecology strategies for the engineering of microbial consortia with applications in diverse fields ranging from remediation, bioprocessing, and ecosystem sciences. Additional benefits result from efforts to help build a microbiome workforce via project-based course development, public outreach, training workshops, and development of instructional tools for K-12 audiences. This project is supported by co-funding from the CHE Chemistry of Life Processes program in the Math and Physical Sciences Directorate and the CBET Environmental Engineering program in the Engineering Directorate. 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.