John Parkes is a microbial ecologist who studies the activity of microorganisms in geological contexts, particularly within the deep subsurface of the Earth. His work has helped to establish knowledge of the existence of enormous populations of bacteria in the deep biosphere, which are of interest due to their close proximity to oil reserves, deep disposal sites and geosphere energy sources.

His research highlights include the use of phospholipid fatty acids as biomarkers for the identification of sedimentary microbes. John has also conducted wider studies of such prokaryotic communities using radioactive tracers and stable isotope probing, in addition to demonstrating the importance of anaerobic prokaryotic processes in estuarine sediments.

John has received many accolades in recognition of his work. He has been elected to the fellowships of the Society of Biology, the American Academy of Microbiology and the Learned Society of Wales.