Pseudomonas denitrificans
Molly Meyer

“Make sure you take your vitamins.” Children all over the world hear these words from their health conscious mothers over breakfast every morning. But vitamins are not just for children anymore. Whether they come in the form of a chewy fruit flavored “Flintstones” cartoon character or even a boring pale yellow oval “One-A-Day” supplement, vitamins add essential nutrients to the diets of millions of people everyday.

On the other hand, people generally try to avoid bacteria in their daily lives. They use antibacterial soaps and hand gels. Reminders to wash our hands come on signs in almost every restroom. Cooks meticulously heat meat to the proper temperature to kill any food-born disease causing microorganisms. The eggs cannot be too runny at the IHOP or the milk left at an elevated temperature too long on the trip home from the grocery store. Household cleanliness has reached new heights with “Swifter Wet Jets” and handy “Clorox Wipes.” Some "germaphobes" even approach door handles and pay phones with caution.

So what do these daily occurrences of swallowing a vitamin and using a gel hand sanitizer have in common? Surprise…they both result from bacteria. Of course, bacteria are a reason to maintain good hygiene, but they also promote health by making certain vitamins available for daily consumption. The bacterium Pseudomonas denitrificans produces Vitamin B12 in great quantities. In fact, under the appropriate conditions 60 milligrams of the vitamin can be produced per liter of these bacteria. Often the bacteria are grown in sugar-beet molasses over 4 days for this process to occur.

Not only is B12 essential for humans, but its only method of synthesis is by prokaryotic microorganisms like Pseudomonas denitrificans. This particular microbe is the main commercial producer of the vitamin. Without vitamin B12 in one’s diet, a person may develop pernicious anemia.

These beneficial bacteria deserve to be introduced. Their genus is Pseudomonas and their species is denitrificans, as the name clearly suggests. But please, just call them P. denitrificans for short.
These prokaryotes possess a coccoid or circular shape. They grow in the presence of oxygen or aerobically. Their food comes in the form of reduced sulfur compounds, and P. denitrificans can be classified as autotrophs or organisms that can use carbon dioxide as a direct carbon source. This microbe can be found in soil and water, its ideal habitat.

How does one develop a name like P. denitrificans? These bacteria did it through their characteristic metabolism. They possess the so-called denitrifying enzyme, nitrate reductase. In their process of nitrate respiration, the terminal electron acceptor of the bacterium is nitrate and reduced nitrogen containing compounds are formed like N2, N2O, and NO2-. Therefore, this microbe also plays a role in the nitrogen cycle by releasing nitrogen back into the atmosphere to be fixed for plants by other microbes.

Evidently, this particular bacterium plays more than one invisible role in our daily lives. The connection between vitamins and bacteria may not be obvious, but it serves as another example of how the view of all microbes as harmful “germs” is a misperception. Many bacteria are involved in beneficial activities in nature and in industry. In this case,P. denitrificans remind us that we have more to thank than our moms for allowing us to take our vitamins.

Alexander, Martin. Introduction to Soil Microbiology. New York: John Wiley and Sons, 1961.
Bergey’s Manual of Systematic Bacteriology. Ed. Noel R. Krieg. Baltimore: Williams and Wilkins, 1984.
Madigan, Martinko, and Parker. Brock Biology of Microorganisms. New Jersey: Prentice Hall, 2003.
Perry, Staley, and Lory. Microbial Life. Massachusetts: Sinauer, 2002.
The Prokaryotes. Ed. Albert Balows. New York: Springer-Verlag, 1992.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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