Science Buddies: "Ask an Expert"

My science fair project consists of using a Dissimilatory Perchlorate Respiring Bacteria, specifically Dechloromonas Aromitica strain RCB, to reduce ammonium perchlorate on the surface of Mars. Perchlorates are toxic to humans and cover every inch of the surface of Mars. The Mars One project is suppose to send two astronauts to Mars in the next decade. Although astronauts wear special protective suits, perchlorates still pose a hazard to the health of anyone near them. So I am in the process of designing an experiment. I know through perchlorate respiration, oxygen and chlorine are produced. And with the Martian's atmosphere being nearly 97% carbon dioxide, I figured the production of oxygen would actually help with life coming back to Mars later in the future. So my project hits two birds with one stone. Not only do I make Mars safer for us, I can also improve the chances of it being inhabitable by other forms of life in the future. I'm having trouble though with several aspects of this project. First, I don't know how to grow this bacteria. MicrobeWiki didn't help much. I plan on cutivating this bacteria and don't know what it likes to grow in or around. I plan on also placing it some kind of solution with ammonium perchlorate. I just don't know what this solution is or what it should consist of. And lastly, I need to be able to measure, over time, if there is any increase of oxygen, for this will indicate perchlorate respiration is taking place. So in conclusion, I need to know what environment is best for this strain of bacteria to grow in, what should the solution consist of, and what device is highly sensitive enough to measure small increases in atmospheric oxygen levels. Thanks to anyone who can assist me with my project. It is definitely appreciated. Have a great day!

I'm not a life science expert, but I did want to welcome a fellow Martian!

The generation of oxygen for astronauts on Mars using local materials is referred to in the literature as in-situ resource utilization, abbreviated ISRU. So, a google scholar search on "Mars ISRU perchlorate" might give you some ideas as to what microbes have been investigated for this purpose. Once you know the name of your microbe, it should be easier to find information on whether science supply houses sell it and what it needs to grow.

Are you working in a lab? If not, you might want to ask a school chemistry teacher about the chemical reaction involved and how to detect the oxygen. Don't forget about the chlorine -- it's a pretty reactive element and has to go somewhere, too!

Great idea! You may be one of the scientists on the first Mars mission and get to test your terraforming method in person.

I had to look up Dechloromonas because I had never heard of that bacterium. It can do some potentially very useful things like digest benzene and other organics as well as reduce perchlorate to form oxygen. And you are right—there’s not much on Google about how specifically to grow these bugs. I checked PubMed to see if there were any papers using Dechloromonas that had culture instructions in the methods section and found some:

http://www.ncbi.nlm.nih.gov/pubmed/12200296
http://www.ncbi.nlm.nih.gov/pubmed/21115710
http://www.ncbi.nlm.nih.gov/pubmed/19650930
http://www.ncbi.nlm.nih.gov/pubmed/19533120

In taking a quick look at these papers, it seemed to me that most of the experiments with perchlorate reduction used D. agitata rather than D. aromatica. Is there a reason why you chose D. aromatica rather than the other species? If one species is better at perchlorate reduction then I would use that one.

I am assuming that you will be able to do your experiments in a lab set up to work with bacteria. Culturing Dechloromonas is going to require some special glassware that will allow you to collect the oxygen that is formed when they are grown in the presence of perchlorate. Instruments to measure the concentration of oxygen are expensive and not many labs would have them. I can’t think of a simple, inexpensive way to measure oxygen, but maybe you don’t have to.

If you set up the culture flasks in such a way that they have an airtight stopper with a tube leading to a graduated collection vessel, all you have to do is measure the volume of gas produced since it will all be oxygen. The bacterial enzyme that breaks down perchlorate [ClO4] is called perchlorate reductase (http://www.uniprot.org/uniprot/Q47CW6) and the result is chlorite [ClO2]. The chlorite in turn is metabolized by chlorite dismutase (http://www.ebi.ac.uk/interpro/entry/IPR010644) to produce chloride [NOT chlorine] and more oxygen.

You will need to keep the temperature of all the flasks constant because changes in temperature cause changes in gas volume. You should also measure barometric pressure during the run to determine if there were any pressure changes that could have altered your results. Most smart phones can measure barometric pressure.

This is a great project and I am really looking forward to seeing your results. It’s going to take a lot of work to set up and run it to get accurate data but it will really be worth it. We can help with the details but you really need to work in a bacteriology lab where they have the glassware, incubators, water baths, autoclave, etc. to do your experiments.

I hope this information is helpful. Post again and let us know more about your plans. We’ll help get you on the road to a successful Martian project!

Good luck!

Sybee