1. Geomicrobiology Group, School of Life Sciences University of Dundee Dundee Scotland DD1 5EH UK
2. School of Science and Engineering, Fulton Building University of Dundee Dundee Scotland DD1 5HN UK
3. State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil and Gas Pollution Control, College of Chemical Engineering and Environment China University of Petroleum 18 Fuxue Road, Changping District Beijing 102249 China