Science Buddies: "Ask an Expert"

Hi, I want to conduct an experiment to see if air pollution has a positive or negative reaction on nitrogen fixing bacteria. These bacteria have an enzyme called nitrogenase which is highly sensitive to oxygen, so decreasing oxygen levels due to air pollution might have a positive impact. I, however, cannot find any nitrogen free agar medium for sale on the web. So does anyone know anything about this. And if anyone has any tips on this experiment, I will be glad to hear them.

Hi and welcome to Sciencebuddies! We're here to guide your project and offer suggestions on how to make it the best possible. Let me see if i understand your hypothesis. You are saying that pollution decreases the percentage of oxygen in the atmosphere. How would that happen and how much of a decrease would there normally be? Would that decrease be enough to have any effect on N2-fixing bacteria? These are questions you need to answer in the planning stage before you jump into the project.

How are you planning to expose the bacteria to air with different concentrations of O2? Do you have access to a microbiology lab where you can control the atmosphere in which agar plates are incubated?

Are you planning to use some type of Azotobacter in your experiments? This bacterium is one that can be grown in air because it is able to use the oxygen in its own respiration. This keeps the level low in the bacterial cells so that nitrogenase is not affected. You might want to use some bacterium that is more sensitive to O2 but then you cannot grow them in air. They must be grown anaerobically.

I looked up nitrogen-free agar and there are several recipes for it or you can buy it.

http://www.google.com/url?sa=t&rct=j&q= ... GU&cad=rja

http://www.google.com/url?sa=t&rct=j&q= ... 7243,d.cGU

https://www.google.com/url?sa=t&rct=j&q ... GU&cad=rja

http://www.google.com/url?sa=t&rct=j&q= ... GU&cad=rja

Send us another post with more details of your experimental plans and we will try to steer your project onto the best path.

Good luck!

Sybee

Wow! Thank You! This really opened my eyes. I don't have access to a Microbiological Lab. I was going to collect soil samples from a farm near an industry, a farm in a very rural place, and a urban garden. Then I was going to count the colonies, but now I see that air pollutants don't decrease the amount of oxygen in the atmosphere. I have, however, found an another topic to experiment. I want to see if bacteria's growth rate increases with the different type of music vibrations. Will you please give me any tips about this new topic. I will be very delighted