Microorganisms play a central role in driving the biogeochemical processes that sustain the planet. My research seeks to unravel the microbial controls on biogeochemical process in natural and engineered environments. Our research has been central in revealing the mechanisms responsible for the development of the world's immense heavy oil deposits - dramatic evidence of the power of the very small to influence globally significant Earth processes. We have also made important contributions to understanding key elements in the microbial ecology of the carbon, nitrogen and sulfur cycles in natural and engineered environments.