Arsenic and Old Lakes
This is not directly related to Tetrahymena but …….. something that may change fundamental ideas about what is required for life is too cool to ignore – even if it doesn’t directly involve my favorite organism. To paraphrase the lead scientist in this work – These findings are not about a specific bacteria or a specific lake site or even arsenic per se. It’s about understanding the fundamental flexibility of life.
Here are 3 links to articles describing work showing that arsenic may be able to replace phosphorus in bacteria living in a very alkaline and hypersaline lake with one of the highest natural concentrations of arsenic on the planet. This bacteria (GFAJ-1 if you prefer) may be able to use arsenic in place of phosphorus in DNA and probably in many other biomolecules.
This article from Astrobiology presents a great write-up that includes a very brief refresher on the role of phosphorus in DNA – short, sweet, and to the point, and complete with a nice diagram. I especially like the conclusion – “GFAJ-1 apparently didn’t read the manual” on phosphorus requirements. There is also a quite readable and understandable explanation of what Dr. Felisa Wolfe-Simon (a women – great to see good female scientific role models) actually did. I really like that there is also a paragraph by a fellow scientist who is skeptical and offers alternative explanations of Wolfe-Simon’s results. It is a great look at how scientists think and work and can disagree when shown identical data – something important for students to think about.
This bulletin from NASA – this is NASA funded research after all – also gives an overview of the project, but I personally like the Astrobiology article better. It is actually interesting to compare the two and see slightly different approaches to discussing the same topic. The NASA article does not give as much basic scientific background and does not really discuss alternate interpretations. There is a neat animation at the end though. This is a good place for a spinoff into how basic research can produce unexpected results!!
Wired also has a really good article as well. I like that the point is made that researchers couldn’t remove 100% of the phosphorus and that there is healthy skepticism about the results and ideas of how to test the validity of the findings, without belittling or negating the possible consequences and importance of the findings. For example, look at the responses of fellow scientists:
““This is an amazing result, a striking, very important and astonishing result — if true,” says molecular chemist Alan Schwartz of Radboud University Nijmegen in the Netherlands. “I’m even more skeptical than usual, because of the implications. But it is fascinating work. It is original, and it is possibly very important.”
““Every organism that we know of uses ATP and phosphorylated DNA,” says biogeochemist Matthew Pasek of the University of South Florida in Tampa. He says the new research is both fascinating and fantastic. So fantastic, that a lot of work is needed to conclusively show exactly how the microbe is using arsenate.”
This kind of dialogue among scientists is generally a part of scientific research that students are not privy to. This article could be part of a lead-in to a great discussion on the dynamic nature of science, differences in interpreting scientifc results, the need for communication between (often competing) groups of scientists, and the importance of a healthy open minded skepticism that leads to ideas for new ways to test changing theories. What a great opportunity to show that science is a dynamic, evolving thing.
If you want details, the original Science article reference was published online at:
A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus
Wolfe-Simon,Felisa; Blum,Jodi Switzer; Kulp,Thomas R.; Gordon,Gwyneth W.; Hoeft,Shelley E.; Pett-Ridge,Jennifer; Stolz,John F.; Webb,Samuel M.; Weber,Peter K.; Davies,Paul C.W.; Anbar,Ariel D.; Oremland,Ronald S. Source:Science
Science 1197258 Published online 2 December 2010 [DOI:10.1126/science.1197258]
There is an interesting response to this article on the Slate website (http://www.slate.com/id/2276919/ ) looking at potential flaws in the work. Again, a great chance to show students that science is not static and that the same data can generate different interpretations. Also stresses the idea that the only way to reach a definitive conclusion is by further research.
Note that the original authors are making the bacteria available to colleagues who wish to try to repeat their work. With other labs trying to repeat the original experiments, any controversy should be resolved fairly soon.