Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Novel bacterium detoxifies chlorinated pollutants

03.07.2003


Researchers have isolated a novel bacterium that flourishes as it destroys harmful chlorinated compounds in polluted environments, leaving behind environmentally benign end products. The finding opens the door for designing more efficient and successful bioremediation strategies for thousands of contaminated sites that remain threats, despite years of expensive cleanup work.



"This organism might be useful for cleaning contaminated subsurface environments and restoring drinking-water reservoirs," Georgia Institute of Technology researchers report in the July 3, 2003 issue of the journal Nature.

The paper, titled "Detoxification of vinyl chloride to ethene coupled to growth of an anaerobic bacterium" is the culmination of five years of field and laboratory studies funded by the National Science Foundation and the Strategic Environmental Research and Development Program.


Scientists and engineers have struggled for years with clean up of groundwater and subsurface environments contaminated decades ago by unregulated use of the common solvents tetrachloroethene (PCE) and trichloroethene (TCE). These toxic compounds are primarily used in dry cleaning operations and degreasing of metal components. Complicating the situation are natural biotic and abiotic processes that transform these solvents to intermediate substances, such as toxic dichloroethenes, and cancer-causing agents, such as vinyl chloride.

But in a step toward engineering better bioremediation strategies, Georgia Tech researchers have isolated a naturally occurring bacterium, designated Dehalococcoides strain BAV1, in a pure culture – without other microbial species present in the sample. Though some progress was made in the past decade in understanding the bacteria involved in partial degradation of PCE and TCE, this study represents a significant advance, researchers said.

"Isolating this bacterium will allow us to study the organism and the dechlorination process in more detail," said lead researcher Frank Loeffler, an assistant professor in the School of Civil and Environmental Engineering. "We can get a lot more information that we can then use to engineer systems in the environment so PCE and TCE degradation would not stop at the toxic intermediate stage, but rather would continue to be dechlorinated to a non-toxic end product, such as ethene."

One site that appears likely to benefit from in-place bioremediation with this bacterium is the Bachman Road residential area contaminated with PCE by a former dry cleaning operation in Oscoda, Mich. There, researchers recently used BAV1 in a successful pilot demonstration, which they briefly reference in the Nature paper. Loeffler and his colleagues described the results of the pilot study in greater detail in a paper published in February 2003 in Environmental Science & Technology.

At this contaminated site, PCE penetrated the water table and contaminated drinking-water wells in the area. The contaminants also migrated through the groundwater into nearby Lake Huron, which attracts sunbathers and swimmers to its beaches and water.

In 14-feet by 16-feet, 20-feet-deep test plots at the Bachman Road site, researchers compared a non-treated control section to two bioremediation approaches using BAV1, which already occurs at this site in low numbers. One strategy, called biostimulation, added lactate and nutrients to the contaminated plot. In another section, researchers injected a mixed culture containing high numbers of BAV1 along with nutrients in a strategy called bioaugmentation. This technique resulted in complete dechlorination of PCE to ethene within six weeks. Biostimulation, on the other hand, worked but took more time to accomplish detoxification.

"Bioaugmentation had a relatively poor reputation," Loeffler said. "In cases targeting petroleum candidates, it didn’t help any more than less expensive strategies. Now, we have a good example of bioaugmentation at work…. It is a viable option, especially at sites with this type (chlorinated solvents) of contamination. So there’s a lot of excitement about this. People have spent a lot of money to clean up those sites without success. Now there’s a new hope."

There are thousands of similar contaminated sites, including military installations where PCE and TCE were once used unregulated as degreasing agents. Both laboratory and field work reported in Nature revealed that the growth of BAV1 depends strictly on the reduction of these chlorinated compounds (e.g., dichloroethenes and vinyl chloride) to ethene and the presence of hydrogen as an electron donor. Also, genetic analyses, analytical chemistry techniques and high-resolution scanning electron microscopy yielded information about the organism’s appearance, makeup and behavior. One peculiarity is filament-like appendages extending from BAV1 cells. Loeffler speculates that these appendages may allow the organisms to colonize contaminated subsurface environments.

Also, phylogenetic analysis described in Nature revealed that BAV1 belongs to the only-recently discovered Dehalococcoides group, which comprises other organisms useful in bioremediation. The findings highlight the largely untapped reservoir of bacterial diversity, Loeffler added.

BAV1’s origin is unknown, though Loeffler believes it evolved long ago, deriving energy from naturally occurring chlorinated compounds, including chlorinated solvents, in the environment. He suggested that BAV1 in some natural areas survives by eating low concentrations of chlorinated compounds formed from volcanic, biologic and possibly ultraviolet light processes. Other scientists assert that BAV1 occurred in the environment long ago, but only developed its chlorinated compound-based metabolism in response to PCE and TCE pollution.

Georgia Tech researchers will continue to learn more about BAV1 as they conduct larger-scale studies, in which Loeffler admits researchers will have a more difficult job in monitoring the dechlorination process. Also, that process may not happen as quickly as it did in the smaller, pilot demonstration. In addition to future studies at the Michigan site, Loeffler is proposing similar research to the U.S. Department of Defense at a TCE-contaminated military installation near Atlanta. There, he expects bioremediation to be complicated by a fractured rock layer beneath the water table.

In addition to opening the doors for further research on BAV1, the Georgia Tech study yielded a molecular technique that likely will be useful to scientists and engineers conducting similar research. The technique allows researchers to quantify the number of BAV1 organisms present at a contaminated site. An increasing number of organisms indicates a positive response to bioremediation efforts. This technique uses a real-time polymerase chain reaction (PCR) device to test field sites.

Loeffler is hopeful about the use of BAV1 and related organisms in bioremediation. He speculates that this group of bacteria might also be useful to treat sites contaminated with polychlorinated dibenzo-dioxins (PCDDs) and polychlorinated biphenyls (PCBs).

"Organisms like BAV1 have an enormous potential to help detoxify chlorinated pollutants," Loeffler said. "But we’re just at the beginning of understanding their function, distribution and ecology in the environment."

The lead author on the Nature paper is Loeffler’s Ph.D. student Jianzhong He, who isolated BAV1 in her professor’s lab. Other authors are postdoctoral fellow Kirsti Ritalahti, who led molecular analyses, graduate student Kun-Lin Yang, who contributed scanning electron microscopy studies, and Stephen Koenigsberg of California-based Regenesis Bioremediation Products, which contributed equipment and materials.

Georgia Tech has filed two patent applications related to Loeffler’s research, and Regenesis is marketing the research team’s culture, called Bio-Dechlor InoculumTM, to the bioremediation community. For more information, see www.regenesis.com/products/bd_inoculum/.


Georgia Tech Research News and Research Horizons magazine, along with high-resolution JPEG images, can be found on the Web at http://www.gtresearchnews.gatech.edu.

Media Contacts:
1. Jane M. Sanders, Georgia Tech, 404-894-2214, or
E-mail: jane.sanders@edi.gatech.edu
2. John Toon, Georgia Tech, 404-894-6986, or
E-mail: john.toon@edi.gatech.edu

For technical information, contact:
1. Frank Loeffler, 404-894-0279, or
E-mail: frank.loeffler@ce.gatech.edu
2. Kirsti Ritalahti, 404-894-5009, or
E-mail krita@ce.gatech.edu

Jane Sanders | EurekAlert!
Further information:
http://gtresearchnews.gatech.edu/
http://www.regenesis.com/products/bd_inoculum

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>