The microorganism Azoarcus tolulyticus is a gram negative bacterium that belongs to the beta subclass of the Proteobacteria. It has an average size of about 1 micron in length. A. tolulyticus is a newly found species in a class of widely distributed toluene-degrading denitrifiers. This particular strain was isolated from a gasoline-contaminated aquifer in Michigan. It has potential importance in the bioremediation of toluene, which is one of the most toxic components of gasoline.
The environmental need for the remediation of toluene comes from the potential contamination that can occur from any gasoline storage tank. Gasoline will sometimes leak from these tanks, even the underground storage facilities used at many gas stations. This escaping gasoline will sometimes carry toluene with it into the water supply. Any wells that tap into a contaminated aquifer will become unfit for human consumption. This problem stresses the need for a toluene degrader, but more specifically an anaerobic toluene degrader.
The aspect of A. tolulyticus that makes it unique from other Azoarcus sp. previously found is that it will operate under anaerobic conditions. It does so by denitrifying nitrate that may be present in anaerobic environments. Therefore, A. tolulyticus is a facilitative anaerobe, meaning it can function and survive in an aerobic environment. This makes the organism easier to work with since it can survive in an oxygen environment. Because many toluene degrading organisms known before A. tolulyticus were all aerobic thry could not grow well in the anaerobic underground environments that many aquifers provide. This is where A. tolulyticus becomes important because if it can grow in the anaerobic conditions of the aquifers, then it could clean up the toluene in that environment.
The anaerobic remediation of toluene proceeds via benzoate as the intermediate, and benzoate is degraded by many microorganisms. The following pathway suggested was compiled from Beller and Spormann 1997, J Bacterial. 179 (3): 670-676 and Biegert et al. 1996, Eur. J Biochem. 238 (3):661-668
Benylsuccinate synthase succinyl-CoA benzylsuccinate CoA-transferase Benzylsuccinyl-Co
AdehydrogenaseToluene ------------------------- > Benzylsuccinate -------------------- > Benzylsuccinyl-CoA ---------------------- > next line) E-phenylitaconyl-CoA E-phenylitaconyl-CoA ------------------------ > (Hydroxymethylphenyl)
succinyl-CoA-------------------- > Benzoyl-CoA ---------------------- > (to Anaerobic Benzoate pathway) The (Hydroxymethylphenyl)succinyl-CoA is also fed back into the system through a number of intermediates to reappear as fumarate in the initial step. A. tolulyticus is useful not only because its ability to degrade toluene anaerobically is good for the water and health, but it is also much cheaper to apply nitrate (which is water soluble) into a gasoline tank than to try to build an aeration system for the tank. Given all the above information on Azoarcus tolulyticus it is certain that this organism will be important in the future.
*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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