Pseudomonas putida
Kris Hamilton

Pseudomonas putida is a bacterium that has caused great excitement and sufficient frustration among scientists. Reasons for these powerful emotions have been the ability of P. putida to break down organic toxins and the difficulty in classifying the Pseudomonads.

Pseudomonas is a genus that contains over 40 species of bacteria; the genus is divided into five groups of classification. The microbes classified in group 1, the group containing P. putida, are true Pseudomonads; however, the microbes in the remaining groups are under careful scrutiny by scientists who believe that they do not belong in the genus Pseudomonas. They are being systematically removed from the genus Pseudomonas and moved to more suitable classifications. This massive genus overhauling has lead to a significant amount of confusion in the biological community. Despite the recent up-rooting of other Pseudomonas species it seems that P. putida is firmly planted within the genus.

P. putida is a rod-shaped, Gram-negative, bacteria officially discovered in the mid 1900’s. It is a very common bug that lives in soil and freshwater environments all over the world where it moves about by way of one or more flagella close to the surface. It plays a very important role in the decomposition that drives the carbon cycle. Tests have shown that P. putida can break down all manner of aliphatic and aromatic hydrocarbons. The only substances that it cannot break down are Teflon, Styrofoam, and organic products containing a single Hydrogen. This has caused microbiologists and environmentalists all around the globe to take notice. P. putida has been shown to have the ability to break down many organic toxins including Atrazine, the worlds most widely used herbicide, into carbon dioxide and water. Atrazine is toxic to wildlife and is also thought to be a carcinogen. Until recently the only way to rid the environment of Atrazine laced earth was to relocate the poisoned dirt to a landfill. Now scientists are developing a system to inoculate the contaminated ground with high concentrations of P. putida in order to rid it of the toxic chemical. P. putida is so effective that it lessens the half-life of Atrazine (8 years) to just 5 ½ hours.

The largest hurdle to overcome in the Bioremediation process is getting the aerobic P. putida to grow deep enough under the soil to effectively break down the Atrazine that has been transported further into the ground by water seeping from the surface. The most promising technique proposed thus far is known as the curtain method. In this application holes are bored down into the earth on the downhill side of where the Atrazine was used and P. putida colonies are placed inside of the grid of holes. As water from the surface seeps down through the surface it picks up the dangerous toxin and carries it through the inoculated grid, removing the toxin from the water. This highly researched method of Bioremediation is under trial in Western Australia where Atrazine has contaminated the water supply of Perth, Australia. We can only hope that the end result is as effective as the research shows it could be.

There was also recent dispute as to how safe this “wonder microbe” really is. Many scientists held fears that P. putida was a pathogenic microbe that could infect the ground water making it unfit to drink. These fears were brought about by the infectious nature of some other microbes in the Pseudomonas genus. P. aeruginosa is a pathogen that infects people, and P. syringae is a disease causing agent for some plants. This was a disputed claim that some microbiologists say is unfounded because P. putida’s upper growth temperature is 35 degrees Celsius. They claim that this means that P. putida cannot live within the human body(37º). They also say that despite many attempts they have never found a case where P. putida caused a disease in plants. Quite to the contrary it has been shown that colonies of P. putida growing within the root structures of plants can actually increase the health of the plant. In the end P. pudita was deemed safe enough to go through with the Curtain project.

P. pudita is an amazing organism that could have far reaching positive effects in the fight to cleanse the world of the toxins that man-kind has been depositing since the use of chemical agents in farming and other industrial processes. The world can only wait and hope that we’ve finally found an answer to the question of how to detoxify the earth and ensure that the chemicals that help us now will not cause us problems in the future.

Distinguishing Characteristics:

• Gram-negative
• Long rod shape
• Non-spore forming
• 1 or more flagella
• Aerobic
• Mesophilic
• Chemoheterotrophic
• Florescent
• Oxidase-positive

Sources:

Palleroni, Norberto. “Human-and Animal Pathogenic Pseudomonads.” The Prokaryotes Volume III, New York: Springer-Verlag,. 1992.

www.abc.net.au/science/news/stories/s25679.htm

www.abc.net.au/science/news/stories/s54259.htm

www-micro.msb.le.ac.uk/video/Pputida.html

http://textbookofbacteriology.net/Pseudomonas.etc.html

*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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