MSB: Do cheaters ever win? Examining microbial competition and extracellular enzyme production

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Microorganisms are highly diverse and perform critical functions in all ecosystems. One of these functions is the cycling of carbon and nutrients from dead plants and animals back into forms that living organisms can use. Microbes catalyze this process by producing extracellular enzymes that operate outside the cell and release small molecules that serve as a food source. However, enzyme production is expensive, and evolution may favor microbes that ?cheat? by intercepting resources from their neighbors without paying the cost of enzyme production. The aim of this project is to determine whether cheater microbes can outcompete enzyme producers, and whether competition depends on environmental factors. The researchers will address this question with Pseudomonas bacteria and bacterial isolates from the ocean.This project is important because global carbon and nutrient cycles depend on microbial enzyme producers. Extracellular enzymes supply nutrients to crop plants, forests, and marine plankton that support land and ocean food webs. If human activities alter microbial communities in ways that promote cheater microbes, these critical functions could be affected. Enzyme production also controls the fraction dead plant and animal carbon that returns to the atmosphere as carbon dioxide. Therefore, the results from this research could help predict future concentrations of greenhouse gases.