Structural characterization of the hydrocarbon degrading bacteria–oil interface: implications for bioremediation

Hydrocarbon degrading bacteria, enriched from an in situ bioremediation site in Long Valley, AZ emulsified and colonized the surface of waste engine oil. The application of a partial dehydration conventional embedding protocol for ultrathin-section transmission electron microscopy preserved the hydrocarbon degrading bacteria–surfactant–oil interface. Bacterial adsorption to oil occurred in association with a highly charged, amphipathic bacterial surfactant interface (25–50 nm thick). This biosurfactant completely encapsulated the emulsified oil droplets demonstrating that less than 1% surfactant (by volume) is required to emulsify waste hydrocarbon during or to promote biodegradation. Growth on oil appeared to occur by the uptake of tens of nm-sized droplets of emulsified oil.