Microbial Observatories: Diversity of Plant-Associated Diazotrophic Bacteria and Their Distributions Within Specific Vegetation Zones Along an Environmental Gradient

University South Carolina Research Foundation, Columbia SC

Investigators

Abstract

A grant has been awarded to Drs. Charles R. Lovell and Madilyn Fletcher of the University of South Carolina (USC) to investigate a group of microorganisms called diazotrophs. These organisms - also called nitrogen-fixing bacteria - play a unique role in nutrient cycling by capturing nitrogen gas from the atmosphere and converting it into forms that can be used by other microorganisms, plants, and animals. Since nitrogen is an essential nutrient for all living systems, the activity of diazotrophs is fundamental to life on this planet. Diazotrophs are extremely diverse, and many are associated with the roots of plants. Most are poorly characterized, while still more remain undiscovered. In this work, diazotrophs associated with salt marsh plants will be characterized to determine the relationships between specific types of diazotrophs, variations in environmental factors, and different host plants. The diazotrophs will be identified and their nitrogen-fixing activity will be assessed using modern genetic techniques. Their association with specific types of plant roots will be determined using molecular probes and advanced microscopy methods. In this way, it will be possible to identify new diazotrophic microorganisms, assess the specificity of their relationships with plants, and determine their abundance and activity over time and space. Because of their ability to fix atmospheric nitrogen, diazotrophs can enhance the productivity of both natural and agricultural systems. The factors that control nitrogen availability and the productivity of salt marsh systems have important implications for a range of restoration and conservation efforts. Moreover, an understanding of diazotroph-plant relationships and the discovery of new diazotrophs may have applications to agricultural and crop systems, which depend on nitrogen levels in soils. This project will have a direct impact on student training through providing graduate student internships and interfacing with the National Estuarine Research Reserve based at the Baruch Marine Field Laboratory (BMFL). The project will also enhance research facilities and training activities at the BMFL and USC, which are located in an EPSCoR state.