Endospores of thermophilic bacteria are widespread in the marine rare biosphere and have been proposed as model organisms for studying microbial dispersal. Hot subsurface oil reservoirs could potentially be 'deep biosphere' source environments for these organisms, whereby they are transported into the cold seabed through natural hydrocarbon seeps. If so, they would co-occur with hydrocarbon-degrading microbes that colonize seep sediments. This project will evaluate the diversity and abundance of spore-forming thermophilic bacteria in marine sediments in and around hydrocarbon seeps of the Gulf of Mexico. The findings of this project will determine whether detection of thermophilic endospores should be integrated in microbial seep prospection as well as used to potentially map marine seabed areas capable of rapid hydrocarbon biodegradation, i. e., for effective bioremediation of oil spills.