Genetic Bioaugmentation

Our research aims to identify physical, chemical and biological parameters which control horizontal gene transfer (HGT) events with the goal of developing more effective in situ bioremediation treatment technologies.HGT is a widespread phenomenon in the prokaryotic kingdom that occurs readily under harsh environments where genetic adaptation is required for the survival of microorganisms. HGT could be useful for bioremediation to shift microbial communities in favor of degrading contaminants of concern. In particular, plasmid conjugal transfer is one of the dominant and well-studied mechanisms of HGT in bacteria, by which resistance to toxicants such as metals and antibiotics as well as the ability to degrade complex organic compounds may be spread. In genetic bioaugmentation, introduction of environmentally-relevant bacteria harboring self-transmissible catabolic plasmids that encode for the degradation of target contaminants stimulates in situ HGT of the plasmids to indigenous microorganisms, thus resulting in an enhanced contaminant degradation potential at the polluted site. Genetic bioaugmentation aims to transfer relevant genes into indigenous microorganisms that have greater fitness for survival in the contaminated environments as opposed to conventional bioaugmentation which relies on the survival of exogenous microorganisms. In fact, HGT has been reported to repeatedly occur naturally in contaminated sites to aid in bacterial adaptation to organic pollutants; therefore, genetic bioaugmentation aims to enhance the naturally-occurring phenomenon to further improve the biodegradation of target contaminants. This approach is likely to receive much more favorable adoption than the use of genetically engineering microorganisms (GEMs) as GEMs are heavily regulated by the US Environmental Protection Agency for in situ bioremediation. To date, GEMs have only been approved for a limited number of cases. We anticipate our findings will be widely applicable to all contaminants and that these fundamental results could ultimately be transferred to the development of new treatment strategies for lesser biodegradable contaminants as well as for the bioremediation of mixed wastes. 

 Horizontal Gene Transfer

This work is based upon work supported by  National Science Foundation under Grant No. CBET-0846437.  

Publications

R. Pei and C.K. Gunsch, “Plasmid conjugation in a mixed activated sludge microbial community”, Environmental Engineering Science, 2009, 26(4):825-831

K. Ikuma and C. Gunsch, “Effect of Carbon Source Addition on Toluene Biodegradation by Escherichia coli DH5a Transconjugants Harboring the TOL Plasmid”, Biotechnology and Bioengineering, 2010, 107(2):269-277.

K. Ikuma and C.K. Gunsch. “Functionality of the TOL Plasmid Under Varying Environmental Conditions Following Conjugal Transfer”, Applied Microbiology and Biotechnology, 2012, In Press. (doi:10.1007/s00253-012-3949-8)

Oral Presentations

C.K. Gunsch*, “Mechanisms of Genetic Adaptation Following Exposure to Anthropogenic Contaminants”, University of Nebraska, Lincoln, NE (March 10, 2008)

K. Ikuma*, R. Pei and C.K. Gunsch, “Effect of Substrate Type on Toluene Biodegradation Following a Horizontal Gene Transfer Event in Escherichia coli DH5?”, Institute of Biological Engineering 2008 Annual Conference, Chapel Hill, NC (March 6-9, 2008).

C.K. Gunsch*. “Bacterial Conjugation in Aquatic Environments and its Relevance to Bioremediation”, Clemson University, Clemson, SC (October 19, 2007).

 K. Ikuma and C.K. Gunsch*. “Genetic Bioaugmentation: Utilizing Horizontal Gene Transfer to Enhance in situ Bioremediation”, Association of Environmental Engineering and Science Professors Meeting, Tampa, FL (July 10-12, 2011)

C.K. Gunsch*. “Genetic Bioaugmentation: Utilizing Horizontal Gene Transfer to Enhance in situ Bioremediation”, University of California, Berkeley, CA (September 23, 2011).

Poster Presentations

 K. Ikuma, R. Holzem*and C.K. Gunsch. “Stimulating Genetic Bioaugmentation in Soil: Impact on TOL Plasmid Transfer Rates and Toluene Biodegradation” Submitted for Presentation at the Association of Environmental Engineering and Science Professors Meeting, Tampa, FL (July 10-12, 2011).

K. Ikuma* and C.K. Gunsch, “Effect of Substrate Addition on Toluene Biodegradation Following a Horizontal Gene Transfer Event of the TOL Plasmid into Escherichia coli DH5a”, 13th International Society for Microbial Ecology Meeting, Seattle, Washington (August 22-27, 2010).

K. Ikuma* and C.K. Gunsch, “Effect of Substrate Addition on Toluene Biodegradation Following a Horizontal Gene Transfer Event of the TOL Plasmid into Escherichia coli DH5a”, Association of Environmental Engineering and Science Professors Meeting, Iowa City, Iowa (July 26-29, 2009)

K. Ikuma* and C.K. Gunsch, “Characterization of Toluene Biodegradation Following a Horizontal Gene Transfer Event in Escherichia coli DH5a and Environmental Bacteria”, BAGECO 10, Uppsala, Sweden (June 15-19, 2009)

K. Ikuma*, R. Pei and C.K. Gunsch, “Characterization of Toluene Biodegradation Following a Horizontal Gene Transfer Event in Escherichia coli DH5?”, Abstracts from the 108th General Meeting of the American Society for Microbiology, Boston, MA (June 1-5, 2008)

R. Pei* and C.K. Gunsch, “Horizontal Gene Transfer Occurences in a Mixed Microbial Community”, Abstracts from the 108th General Meeting of the American Society for Microbiology, Boston, MA (June 1-5, 2008).