Controversy over a bacterium that grows in arsenic — Can arsenic sustain life? Controversy over a bacterium that grows in arsenic — Can arsenic sustain life? – SOMETHING ABOUT SCIENCE

Controversy over a bacterium that grows in arsenic — Can arsenic sustain life?

The scientific community has been very busy debating over a controversial issue surrounding a bacterium from California.

English: Felisa Wolfe-Simon at the 2011 Time 1...

Dr. Felisa Wolfe-Simon. Photo credit: Wikimedia Commons

It all started when NASA astrobiology fellow Dr. Felisa Wolfe-Simon and her team published a research article in Science in December 2010. Wolfe-Simon and colleagues have isolated a strain of bacterium called GFAJ-1 from arsenic-rich Mono Lake, California. In the paper, the authors reported that this GFAJ-1 can grow in arsenic cultures without phosphorus.  Furthermore, they announced that the bacterium can incorporate arsenic into essential biomolecues, including DNA and proteins.

This finding was striking because our understanding is that organisms on Earth require six elements to sustain life: oxygen, carbon, nitrogen, hydrogen, sulfur, and phosphorus.  If the bacterium GFAJ-1 can indeed replace phosphorus with arsenic, it would be a new discovery in metabolism; suggests that life on Earth may have started with elements other than the six canonical elements listed above; and it may point out the possibility of extraterrestrial life that exist in hostile environments that we previously thought would not sustain life.

English: GFAJ-1 grown on arsenic.

GFAJ-1 grown in arsenic. Photo credit: Wikimedia Commons

Arsenic is an analog of phosphorus, placed right below phosphorus on the periodic table. Because arsenic can be mistaken for phosphorus inside our cells, it is a very toxic chemical in our bodies. Researchers are excited to discover bacterium that can use arsenic instead of phosphorus, as it suggests a metabolism very different from ours.

However, Wolfe-Simon and her team has met very harsh criticism from other researchers, where they see the finding as “preliminary,” “uncertain,” “speculative,” and “unconvincing” among other skeptical comments.

Here are some of the concerns raised from other scientists:

–          Arsenate linkages are much more unstable than phosphate linkages (which are found in biomolecules, such as DNA). The estimated half-life of arsenic-containing DNA is about 1min, whereas half-life of phosphorus-containing DNA is about 30 million years. With such instability, how can arsenate linkages remain intact for detection?
–          GFAJ-1 could be arsenic-resistant extremophile (robust microbe living in extreme conditions) and could simply be using trace amount of phosphorus in the bacterial culture rather than using arsenic.
–          The research article is missing the data that shows arsenic being actually incorporated into DNA and other biomolecules. Additional data are needed to prove that arsenic is replacing phosphorus from biomolecules of GFAJ-1.
–          Microbiologist Rosie Redfield from the University of British Columbia could not reproduce the work of Wolfe-Simon and her team and suspects that the finding is incorrect.

When will this debate come to an end? Probably not in the near future. Controversial scientific findings require input from multiple scientists. Further data must be put forth to support the discovery, which then must be repeated by others for confirmation.

Steps are being taken towards the verdict. Wolfe-Simon and her team have made GFAJ-1 available to other researchers for tests, and the team is collaborating with other groups for further experiments. Wolfe-Simon herself is now looking for a new lab where the facility is better suited for the experiments she plans to do. (On a side note, GFAJ-1 can stand for “Give Felisa a Job,” as one of the scientists has pointed out.)

I will cover this topic again once new progress has been made in the area. Stay put!

Don’t forget to come back in a week for the next post! 🙂

References:

Original research article by Wolfe-Simon and others
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Comment on “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”
Response to Comments on “A Bacterium That Can Grow Using Arsenic Instead of Phosphorus”
Open Science Research Blog of Rosie Redfield
Concerns About Arsenic-Laden Bacterium Aired
What job can a bug give? A controversy over the arsenic-guzzling bacterium cultured by NASA (“Give Felisa A Job”)

Lynn Kimlicka

I am a scientist-turned writer and editor, who loves to read and write (more than doing experiments). I have a PhD in biochemistry and molecular biology, with a specialization in structural biology. My interests range widely, from life sciences to pop culture and arts to music. I am bilingual in English and Japanese.

1 Response

  1. July 30, 2012

    […] arsenic into its essential biomolecules, including DNA and proteins. (For more recap, check out my older post.) Arsenic is very similar to phosphorus. However, unlike phosphorus which is essential to living […]

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