Of Aliens and Arsenic

Or How to Screw up an Interesting Discovery with Mediocrity and Media Hype

NASA annonced an “astrobiology discovery”….Aliens! No, sorry, bacteria…in California! WOW! OK, this is no ordinary bacteria as it can grow in astonishing concentrations of arsenic, a highly toxic compound. It’s nothing new that bacteria can grow in all kinds of extreme environments, but this is growth in a lot more arsenic than we’ve seen before. The claim however is that this bacterium actually replaces phosphorus with arsenic. Phosphorus is used as part of the structure of DNA, as well as proteins and many important small metabolites, most notably ATP, used as an energy source. Arsenic is much like phosphorus but arsenic containing compounds are quite unstable in water (which is why arsenic is toxic). This would be novel in cellular life as we know it; DNA containing arsenic! I was initially very interested in this discovery…and then I read the paper.
When you make a claim as big as replacing one of the most import elements in a cell, it seems to me your data better be rock solid. The paper is quite underwhelming. Although it seems there might be arsenic associated with the DNA it certainly doesn’t provide good evidence that it’s a part of its structure. In fact, others have argued more convincingly that the trace amount of phosphorus contaminating the preparation is sufficient for the cells to use to make everything they would need to.
It seems to me this is a case of the researchers jumping ahead of themselves and interpreting something from the data that is just not there, a failure of the peer review system, and an overly enthusiastic media running with a thrilling but incorrect story about alternative branches of life and our need to re-write biology textbooks. Whats sad is that there actually is something interesting here that has been missed and would be a more reasonable interpretation of the data. This bacteria can grow at extreme concentrations of arsenic, in the near absence of phosphorus, but can still somehow scavenge those few available atoms of phosporus and use them, where probably all other organisms would have long since died of arsenic poisoning. How does it do that? This is still a fascinating bacterium…it just wont redefine life.
FInally, why am I writing about bacteria on a virology blog? I learned some time ago never to underestimate viruses. After being surprised about the existence of viruses infecting organisms in places like bubbling geothermal acid pools, I realized that where there are cells, there are viruses. I wonder if this arsenic loving bacteria is host to some interesting viruses? I bet Mono Lake, where this discovery was made, is full of interesting viruses.