Pollution from petroleum spills or leaks can have negative impacts on ecosystems. The importance of bacteria for biodegradation of petroleum is well described for contaminated seawater and coastal soils, but very little is known about the role of plant symbionts in degrading petroleum. Endophytes are bacteria and fungi that live as symbionts within plant roots, stems and leaves. These symbionts are closely associated with the plant and some endophyte species may serve the dual purpose of promoting plant growth and degrading petroleum inside of plant tissues. In an extreme environment such as a salt marsh, where oxygen is limited in soils, plants may be especially dependent on endophytes for resilience to stress and to respond to petroleum contamination.
Our research addresses the questions: (1) do endophyte communities inside of coastal plants shift to incorporate and amplify endophytes that are tolerant to petroleum and can biodegrade it? And (2) do plants deliver oxygen and endophytes to polluted soils, thereby hastening the chemical evolution of petroleum? We combine field, greenhouse, microbiological and molecular studies to address these questions.
With respect to past oil spills, our work since the Deepwater Horizon (DWH) oil spill has shown that when coastal grasses are contaminated with petroleum, fungal endophyte abundances are generally low. Bacterial endophyte abundances remain high, but the communities shift to incorporate more taxa with known roles in biodegradation. Regarding petroleum pollution in the present, we use greenhouse studies to profile the symbiont communities and plant growth parameters in the presence and absence of petroleum. We further compare the breakdown of petroleum in the presence and absence of plant/symbiont combinations. Looking toward the future, our goal is to develop a mechanistic understanding of how grasses, symbionts and polluted soil interact. This knowledge will hasten the development of remediation tools that use plant-delivered, naturally occurring symbionts to clean up polluted soils and protect shorelines.