Role Of Non-Phototrophs In The Growth And Fitness Of Biological Soil Crust

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Biological soil crusts (or “biocrusts”) are communities of microorganisms that develop naturally on the surface of soil from arid and range lands based on the photosynthesis of tiny, plant-like organisms known as cyanobacteria. In unaltered settings biocrust can cover much of the landscape, providing several important benefits to the ecosystem. They can take up nutrients from the air, for example, increasing soil fertility. And, importantly, they build veritable surface crusts that protect the soil from erosion by wind and water and prevent the formation of fugitive dust. Their effects are measurable both locally and globally. Unfortunately, biocrusts are negatively impacted by several human activities, including cattle grazing, agriculture, urban sprawl, and global warming, among others. This often leads to the degradation of soil quality and increases in fugitive dust formation. During the last decade, the rehabilitation of biocrust has become a goal in ecological restoration efforts in many countries, including the US. However, less than optimal outcomes on this front made it patent that knowledge about the basic biology and ecology of these communities is insufficient. While we have learned much about the biology of the all-important photosynthetic microbes that build these crusts, the lack of success in producing new crusts pointed to some yet unknown factor or factors that are crucial for their growth and overall fitness. This research focuses on the non-photosynthetic microbes that establish specific biological relationships with the photosynthetic microbes. This project will provide training to graduate and community college students and will provide critical information necessary to advance biocrust restoration.The project will address this knowledge gap experimentally by first rigorously identifying and characterizing the main non-photosynthetic microbial actors involved in such interactions using a combination of pedigreed cultivation and molecular approaches. Subsequently, the project will study the mechanistic nature of the interactions at play, by reconstructing the mutualistic interactions in culture and by experimentally disrupting the need for a mutualistic interaction in field samples. Finally, the project will assess the importance of these interactions as determinants of growth and fitness in natural biocrusts. Because of their particularly crucial role, the project will focus on microbial interactions with pioneer cyanobacteria and on early stage biocrusts. The plan calls for three discrete tasks, each driven by specific hypotheses based on preliminary evidence. These are: 1) that interactions are a staple of pioneer biocrust forming cyanobacteria, 2) that these are based on mutualisms that are specific with respect to purpose and partner, and 3) that predatory bacteria constitute a universal, ecologically significant loss factor in biocrusts. The project includes efforts to involve stakeholders in land management, to facilitate technological transfer, and contributes significantly to science workforce development at various levels.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.