A new study highlights the importance of hydrogen as an energy source for chemosynthetic bacteria in the deep sea. Surprisingly, this appears to be the case not only near deep-sea hydrothermal vents where there is abundant hydrogen, but also far from vents where the source of hydrogen is unclear. The results have implications for understanding the cycling of carbon in the oceans because carbon cycling is influenced by the distribution of energy sources in the ocean. The study also shows that a widespread group of marine bacteria is quite dynamic; different populations of these bacteria appear to tune their genomes and metabolism to varying local environmental conditions. 

Read the abstract here:

http://www.pnas.org/content/110/1/330.abstract