Skip to main content

Journal Club:”A Bacterium That Can Grow by Using Arsenic Instead of Phosphorous”


Since the previous journal club where we covered an article that looked at the microbial synthesis of alkanes, another a curious observation made the rounds in the science world. In the latest Science Journal, Felisa Wolfe-Simon et. al. report their successful isolation of a bacteria that can use arsenic instead of phosphorous.

The group isolated the bacterial strain called, GFAJ-1, by inoculating synthetic media containing glucose, vitamins and trace metals and varying concentrations of AsO43- with sediments from Mono Lake which naturally contains high concentrations of dissolved arsenic (200 M) and performing many serial dilutions. GFAJ-1 was identified to belong to Halomonadaceae family of Gammaproteobacteria.


Various tests were performed to verify that these organisms could not only live but procreate in this environment. Among the remarkable features of this organism is the observation that arsenic can get incorporated into macromolecules most notably DNA where it replaces the need for phosphorous in the backbone. Despite similar chemical properties of AsO43-and PO43- down-stream processes can be affected by the presence of AsO43-explaining the toxic effects of arsenate. It is even more remarkable that this bacterium can switch between the use of AsO43- and PO43-although it has to be noted that the organisms grow much faster in media containing phosphate instead of arsenate. Details on how arsenic was incorporated into macromolecules and how the organism can deal with varying concentrations of arsenic and phosphorus are currently unknown but will surely be part of future publications.


Why is this so important?


There has been the long-standing view that life on earth is mostly based on carbon, hydrogen, nitrogen, oxygen sulfur and phosphorus. The observation that phosphorus which builds the backbone of DNA can be replaced by arsenic expands the view of possible biochemistry that can take place in other parts of the universe.


From an environmental point of view, dissolved arsenic is toxic to most life due to the similar but but not quite identical properties of arsenic which allows some reactions to take place while inhibiting others. Could bio accumulation of arsenic by used to clean up arsenic contamination sites? 


P.S (2011-02-18).: The journal club would not be complete if I did not mention that some people remain skeptical of the claim that arsenate can replace phosphate in these organisms. The criticicsm centers around some of the assumptions underlying some of their indirect methodologies. An alternative hypothesis was suggested: Rather than arsenate incorporation, some scientists hypothesize that arsenate is rather sequestered. Great claims require great proofs which in the minds of these scientists had not been brought forward. In response to the criticism the author decided to submit the strain to two publically available culture collection centers (the American ATCC and the German DSMZ) to allow for their more widespread studies.
 
Literature Cited:


Felisa Wolfe-Simon et. al. "A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus."
Science Express, December 2, 2010, pp 1-9

Link: http://www.sciencemag.org/content/early/2010/12/01/science.1197258.full.pdf

Popular posts from this blog

Sustainable Living: Sunscreens

This is an important topic and so I want to get the most important things out of the way first:

Chemical sunscreens containing the following ingredients contribute to coral bleaching: 
OxybenzoneOctinoxateOctocrylene (used to also stabilize avobenzone)4-methylbenzylidine camphorAnything containing Parabens Don't be part of the problem and avoid using them! It's important to note that claims on sunscreens are not regulated and therefore, companies can put the wording "coral reef safe" on the packaging even though they contain the above chemicals. This is misleading if not outright false. Instead use "physical" sun screens that contain non-nanoparticle zink oxide. Physical sun screens differ from chemical sunscreens in that the sit ontop of the skin to reflect or scatter UVA/B rays away from the skin before it reaches it. Chemical sunscreens absorb the UVA/B rays instead to neutralize them.

To be clear, I am not proposing not using sunscreen! Instead use phys…

Focus on Algae - Part II: Energy

In the last focus section, we discussed how algae can be used to treat waste waters and mitigate CO2 in the process. Today's post will explore how algae can be used for energy generation. As already mentioned in the last time, biofuels have become very visible as of late due to environmental, economical and geopolitcal reasons. If at the heart of traditional biofuel generation lies in the creation and decomposition of biomass, then it would be easy to substitute corn or other less controversial land-based plants with algae. Although a lot of attention is paid to the use of algae in biofuel generation, and this article also mainly focusses on this aspect, it should be noted that algae can also be used to generate electricity by direct combustion of the biomass. Plans for these kinds of schemes are already on the way in Venice and a few other European locations [1].

Algae and Biofuels

What happens to the biomass after it has been created depends on the type of biofuel that is desired…

Sustainable Living: One man's trash...

Since Earth Week is starting tomorrow, I wanted share with you some concrete ways of how individuals like you and me can make an impact on a wider scale. I then also wanted to use this example to challenge everyone to think creatively about the larger context.

So you know how the saying goes: "One man's trash is another one's treasure." Today, I want to talk to you about garbage. Plastic garbage specifically. Plastic is quite a wondrous material. Made from oil by man with just a few additives can turn this polymer into so many different sorts of plastics with so many different properties from thin and flimsy plastic bags, to the carpet on which I am standing, to this plastic bottle from which I am drinking.