Animal Pavillion

Anaerobic Toluene Degrader

Click here to see a JPEG of this microbe.


Kingdom: Eubacterium
Scientific Name: Azoarcus tolulyticus
Image Courtesy of: Shirley Owens and Catherine McGowan
Image Width: 3.5 microns
Image Technology: SEM (Scanning Electron Microscope)

This bacterium is an anaerobic toluene degrader. It was isolated from a gasoline-contaminated aquifer in Michigan. This organism was isolated and studied by Joanne Chee-Sanford as part of her doctoral dissertation research. It is being displayed as our "Microbe of the Week" (during April 1996) in honor of Dr. Chee-Sanford's recent successful defense of her dissertation project.

Toluene is one of the most toxic components of gasoline. Gasoline sometimes leaks from storage tanks (particularly older ones), including underground ones found at many gas stations. Leaking gasoline, and with it toluene, often finds its way into underground water supplies. Wells that tap into such aquifers can become contaminated with toluene, making them unfit for human use. Bacteria that degrade (break down) toluene are being studied as a possible way to bioremediate (clean up) such contaminated water supplies.

Although aerobic toluene-degrading microbes had been isolated previously, this bacterium was one of the first anaerobic toluene degraders found. Aerobic microbes need oxygen to survive and to produce energy (in a sense, they "breathe" oxygen, like we do). Anaerobic microbes don't need oxygen; instead they "breathe" other substances to use for energy processing. Anaerobic microbes can survive in many environments that don't have a ready supply of air, such as in stagnant water or underground.

Toluene-degrading bacteria that are aerobic cannot thrive in wet, underground environments like many aquifers. Sometimes bioremediation is accomplished by giving microbes a helping hand. If we could get oxygen to aerobic toluene degraders in contaminated aquifers, they might clean up our mess for us. Unfortunately, pumping oxygen into water supplies is not very feasible. Because of this, scientists are interested in finding anaerobic toluene degraders, such as this one. This bacterium "breathes" nitrate instead of oxygen. Nitrate is soluble in water, so it might be possible to help it clean up a water supply by dissolving nitrate into the water. Providing these bacteria with an abundance of nitrate might enable them to create lots of energy in support of a rapid metabolism, thus enabling them to gobble up lots of toluene. This bacterium can function either as an aerobe or as an anaerobe, breathing either oxygen or nitrate. Scientists are particularly interested in its anaerobic metabolism because of its implications for bioremediation.

The specimen shown here is in the process of dividing to form two new bacterial offspring. The narrow section in the middle is where this bacterium will split apart.