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This article could have been a little less disingenuous. It would still have been a very good article if you had used “sulfuric acid” instead of “odorless hydrogen sulfate” and admitted that the process still required a little alkali to neutralize this waste stream that is “carried away by water trickling over the foam.”

Jim Nottke
Pfafftown, N.C.

I would have liked it if the article had mentioned something more about where the bacteria for this were found. Do they occur naturally around us? Were they isolated from deep-sea hydrothermal vents?

Richard Fellows
Pleasanton, Calif.

The investigators used a mixture of naturally occurring bacteria from soil and other nonextreme environments .–J. Travis