Georgia’s saltwater marshes are important ecosystems along the state’s 100-mile coastline, dominated by cordgrass, which serves as an ecosystem engineer. These grasses provide habitats for wildlife, clean water naturally, prevent shoreline collapse, and protect communities from tidal surges. While the Georgia coastline has a rich history of ecological research, the interaction between bacteria and plants in these ecosystems has been poorly understood until recently. Advances in genomic technology have allowed Georgia Tech biologists to uncover new ecological processes, shedding light on the role of bacteria in maintaining the health of cordgrass plants.
Joel Kostka and Jose Luis Rolando from Georgia Tech investigated the relationship between cordgrass Spartina alterniflora and the microbial communities living in their roots, identifying the bacteria and their roles. Just like humans rely on gut microbes for health, plants depend on microbes for various functions such as immunity, metabolism, and nutrient uptake. The researchers focused on nitrogen fixation, a process where bacteria convert nitrogen into a form plants can use. Chemoautotrophs, bacteria that consume toxic sulfide, play a key role in this process, providing energy for the plant. By studying the microbial processes in cordgrass roots, the researchers discovered the importance of chemoautotrophic sulfur-oxidizing bacteria in nitrogen fixation and overall plant health.
Conducting fieldwork on Sapelo Island, Georgia, the researchers collected cordgrass and sediment samples to study microbial communities associated with the plants. By using isotopic tracers and genomic sequencing techniques, they were able to track microbial processes and identify the types of bacteria present in the roots of cordgrass. Their findings revealed that chemoautotrophic sulfur-oxidizing bacteria not only detoxified the root zone by consuming sulfide but also played a crucial role in providing nitrogen to the plants, enhancing their health and resilience. This dual role highlights the importance of these bacteria in coastal ecosystems and their contribution to plant growth.
The significance of this research extends beyond Georgia’s salt marshes, as cordgrass and the associated bacteria are found in coastal ecosystems across the Southeast and globally. These microbial interactions impact ecosystem functioning on a global scale, emphasizing the importance of understanding the relationship between plants and microbes in coastal wetlands. The researchers plan to further explore how marsh plants and microbes exchange nitrogen and carbon using advanced microscopy techniques and mass spectrometry at the single-cell level to confirm their findings. The complexity of these relationships underscores the need for continued research to uncover the mechanisms that keep marshes healthy and thriving.
Overall, Georgia Tech’s research on microbial communities associated with cordgrass in salt marsh ecosystems provides valuable insights into the ecological processes that sustain these important habitats. By identifying the roles of bacteria in nitrogen fixation, detoxification of sulfide, and overall plant health, the researchers are shedding light on the intricate relationships that exist between plants and microbes in coastal ecosystems. The global significance of their findings underscores the importance of further exploration in understanding the microbial complexity that supports the health and resilience of marsh ecosystems.