"This system is a very tightly coupled biogeochemical system, and we are just trying to find out how it works," she said.
"This microbial community is thriving at the extreme edge," added co-author Bob Hettich, a member of ORNL's Chemical Sciences Division. "A pH level of 0.8 is like swimming in sulfuric acid, so we'd like to know how this community can survive and how we might be able to use this information to better understand microbial systems in real-world conditions."
Bacteria, along with ancient microbes called Archaea, in the biofilm capture carbon and nitrogen from the atmosphere and derive energy from iron that has been leached out of the iron sulfide rock, also known as pyrite or "fool's gold." In the process, they produce sulfuric acid that leaches more iron from the pyrite and releases other heavy metals.
Last year's feat gave Banfield's team the nearly complete genomes of the five major bacteria in the biofilm, four of them new to science. The current study now provides nearly half the proteins predicted to be produced by the dominant bacteria, a Leptospirillum group II bacterium, and a smaller proportion from the other bacteria. The lesser coverage of the minor bacteria in the community is due in part because their genomes are more fragmented and in part because these bacteria are in lower concentrations, so their proteins are at correspondingly lower concentrations.
"We identified 48 percent of the product