Bruce M. Greenberg

Cross-appointed (Chemistry)
Undergraduate Advisor (Biochemistry)
Bachelor of Science (BSc) California Berkeley
Doctor of Philosophy Colorado

Email: greenber@uwaterloo.ca

Telephone: (519) 888-4567 ext. 33209

Office: Biology 2 154A

Research interests

Environmental Chemistry and Biology

Phytoremediation of xenobiotic contamination; ultraviolet radiation mediated photochemistry and photobiology. My research addresses novel remediation strategies, using plants and microbes, for in situ removal of contaminants; and impacts of sunlight on environmental biology and chemistry. The focus is on three projects: Plant growth promoting rhizobacteria (PGPR) enhanced phytoremediation of persistent environmental contaminants; photoinduced toxicity of environmental contaminants; effects of UVB radiation on plants. These projects involve molecular, biochemical, photochemical, photobiological, microbial, and whole organism techniques.

PGPR enhanced phytoremediation systems (PEPS) for removal of environmental contaminants in the field

Although numerous mechanical and biological strategies have been implemented to remove persistent organic pollutants from contaminated soils, limitations of these techniques result in sub-optimal rates of remediation. We have developed PGPR enhanced phytoremediation systems (PEPS) combining land farming (aeration and light exposure) and enhanced phytoremediation (combined use of tolerant plant species and PGPR). This synchronous application of multiple techniques improves the remediation process by capitalizing on the benefits of each. Thus far, the system has been used to effectively remove polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHC), salt and metals from impacted soils in the greenhouse and the field. Using the PEPS, we have achieved an accelerated and more complete remediation of recalcitrant compounds. About 90% of PHC were removed from oil sludge contaminated soil during an eight month period in the greenhouse. In a four-month trial period with PAH-contaminated soil from a 50-year old weapons foundry, the PEPS removed 55% of the PAHs. We are currently testing the applicability of the PEPS to remediate a broad range of environmental contaminants, in a variety of soil types, in different geographic areas. We have successfully performed in situ remediation of PHC impacted soils at several sites in Canada, and pilot field studies for remediation of salt impacted sites have shown promising results. We are now adapting the PEPS for remediation of urban brownfield sites. Internationally, we have successfully deployed our phytoremediation technology in China for remediation of herbicide and salt contaminated soils.

Photoinduced toxicity of environmental contaminants

Two ubiquitous groups of contaminants in the environment are metals and polycyclic aromatic hydrocarbons (PAHs). Although they are often co-contaminants, the toxic interactions of metals and PAHs have received little attention. Reflecting their known hazards, the environmental release of metals and PAHs is governmentally regulated. However, the regulatory limits for metals are more severe (e.g. approaching their detection limits). A driving force for the low limits on metals is that some environmental samples with low metal content have been found to have higher than expected toxicity. One reason for these differences could be variability in bioavailability. Another reason is that other environmental factors (e.g. heat, pH or co-contamination) could be impacting on metal toxicity. In particular, it is rare to find environmental sites contaminated with only metals.

Common co-contaminants with metals are PAHs and oxidized PAHs (oxyPAHs). Relevant to this, we discovered that a metal (Cu) and an oxyPAH (1,2-dhATQ) are synergistically toxic (Babu et al., 2001). This is because the oxyPAH inhibits photosynthesis and mitochondrial electron transport, and the metal catalyzes electron transport from the blocked bioenergetic pathways to oxygen. This results in catalytic production of reactive oxygen species (ROS). We believe the catalytic production of ROS to be an extremely important mechanism of metal toxicity. It may also explain metal toxicity at low concentrations, because the effects of the metal will be amplified through catalyzed formation of ROS.

Effects of UVB on plants

As depletion of the stratospheric ozone layer continues, plants will be exposed to increasing levels of UVB. We are examining the ability of the oilseed crop plant Brassica napus to acclimate to UVB stress. The long range goal is the development of crop plants that are tolerant to elevated UVB radiation. We have shown that ribulose-bisphosphate carboxylase oxygenase (rubisco) is photomodified via UVB-induced cross-linking of a large subunit of the protein to a small subunit within the holoenzyme. This photomodification process is being examined in vitro to probe the mechanism of UVB damage to proteins. Although relatively sensitive to UVB, we found Brassica to have clear acclimation mechanisms. Brassica synthesizes UV screening epidermal flavonoids in response to UVB. The increased flavonoid levels protect photosystem II from UV damage. We have also discovered that accumulation of these UVB inducible flavonoids is affected by far red light. We are currently exploring the ability of UVB inducible flavonoids to protect rubisco from UVB photomodification, in the presence and absence of far red light. Lastly, we found that when Brassica cotyledons are exposed to 1 h of UVB followed by a 24 h incubation in visible light, they curl up-wards in response to the UVB. This photomorphogenic response is being studied by action spectroscopy to better characterize the UVB photoreceptor(s).

Selected publications

• Greenberg, B., P. Gerwing and X-D. Huang (2011) A novel phytoremediation technology used to successfully treat salt impacted soils in situ. Canadian Reclamation 11(2), Fall/Winter 2011, 8-12.
• Smith, B., B. Greenberg and GL Stephenson (2011) Bioavailability of copper and zinc in mining soils. Arch. Environ. Contam. Toxicol. DOI 10.1007/s00244-011-9682-y, published online May 19, 2011.
• Smith BA, BM Greenberg and Gl Stephenson (2010) Comparison of biological and chemical measures of metal bioavailability in field soils: Test of a novel simulated earthworm gut extraction Chemosphere 81: 755-766.
• Ashtar, TA, HA Lees, MA Lampi, D Enstone, RA Brain and BM Greenberg (2010) Photosynthetic redox imbalance influences flavonoid biosynthesis in Lemna gibba. Plant Cell Environ. 33: 1205-1219.
• Cowie, BR, BM Greenberg and GF Slater (2010) Determination of microbial carbon sources and cycling during remediation of petroleum hydrocarbon impacted soil using natural abundance (14)C analysis of PLFA. Environ. Sci. Technol. 44: 2322-2327.
• Huang, X-D, X-M Yu, K Gerhardt, B Greenberg and P Gerwing (2009) Plant-growth promoting rhizobacteria (PGPR) enhanced phytoremediation systems (PEPS) for effective on-site degradation of petroleum hydrocarbons in soils. HazMat Management, Fall Issue, 27-31.
• Liddycoat, SM, BM Greenberg and DJ Wolyn (2009) The effect of plant growth promoting rhizobacteria on asparagus seedlings and germinating seeds subjected to water stress under greenhouse conditions. Can.J. Microbiol. 55: 388-394.
• Wang, W., J. Nykamp, X.-D. Huang, K. Gerhardt, D.G. Dixon and B.M. Greenberg. 2008. Examination of the mechanism of phenanthrenequinone (PHQ) toxicity to Vibrio fischeri: Evidence for a ROS mediated toxicity mechanism. Environ. Tox. Chem., accepted for publication.
• Gurska, J., W. Wang, X.-D.Huang, K. Gerhardt, A. Khalid, D. Isherwood, B. Glick and B.M. Greenberg. 2008. Field test of a phytoremediation system utilizing plant growth promoting rhizobacteria at a land farm for treatment of hydrocarbon waste. Environ. Sci. Technol., accepted for publication.
• Gerhardt, K.E., X.-D. Huang, B.R. Glick, and B.M. Greenberg. 2008. Phytoremediation of organic soil contaminants: Potential and challenges, Plant Science, in press.
• Wang, W., M.A. Lampi, X.-D. Huang, K. Gerhardt., D.G. Dixon and B.M. Greenberg. 2008. Assessment of mixture toxicity of copper, cadmium and phenanthrenequinone to the marine bacterium Vibrio fischeri. Environmental Toxicology, in press, published online June 17 2008, DOI 10.1002/tox.20411.
• Gerhardt, K.E., M.A. Lampi and B.M. Greenberg. 2008. The effects of far red light on plant growth and flavonoid accumulation in Brassica napus in the presence of ultraviolet B radiation. Photochem. Photobiol. 84: 1445-1454.
• Greenberg, BM, X.-D. Huang, P. Gerwing, X.-M. Yu, P. Chang, S.S. Wu, K. Gerhardt, J. Nykamp, X. Lu and B. Glick. 2008. Phytoremediation of salt impacted soils: greenhouse and the field trials of plant growth promoting rhizobacteria (PGPR) to improve plant growth and salt phytoaccumulation. In: Proceeding of the 33rd AMOP Technical Seminar on Environmental Contamination and Response, Environment Canada, Ottawa, ON, Vol. 2, pp. 627-637.
• Greenberg, B.M., X.-D. Huang, K. Gerhardt, B.R. Glick, J. Gurska, W. Wang, M. Lampi, A. Khalid, D. Isherwood, P. Chang, H. Wang, S.S. Wu, X.-M. Yu, D.G. Dixon and P. Gerwing. 2007. Field and laboratory tests of a multi-process phytoremediation system for decontamination of petroleum and salt impacted soils (PDF), In: Proceedings of the Ninth International In Situ and On-Site Remediation Symposium. Gavaskar, A.R. and Silver C.F., eds., Batelle Press, Columbus, OH, Chapter B-04 (electronic publication).
• Lampi, M.A., J. Gurska, X.-D. Huang, D.G. Dixon and B.M. Greenberg. 2007. A predictive QSAR model for the photoinduced toxicity of PAHs to Daphnia magna using factors for photosensitization and photomodification. Environ. Toxicol. Chem. 26: 406-415.
• Xie, F., M.A. Lampi, D.G. Dixon and B.M. Greenberg. 2007. Assessment of the toxicity of mixtures or nickel of cadmium with 9,10-phenanthrenequinone to Daphnia magna: Impact of a reactive oxygen-mediated mechanism with different redox-active metals. Environ. Toxicol. Chem. 26: 1425-1432.
• Xie, F., S.A. Koziar, M.A. Lampi, D.G. Dixon, W.P. Norwood U. Borgmann and B.M. Greenberg. 2006. Assessment of the toxicity of mixtures of copper, 9,10-phenanthrenequinone, and phenanthrene to Daphnia magna: Evidence for a reactive oxygen mechanism. Environ. Toxicol. Chem. 25: 613-622.
• Greenberg, B.M., X.-D. Huang, Y. Gurska, K.E. Gerhardt, W. Wang, M.A. Lampi, C. Zhang, A. Khalid, D. Isherwood, P. Chang, H. Wang, D.G. Dixon and B.R. Glick. 2006. Successful field tests of a multi-process phytoremediation system for decontamination of persistent petroleum and organic contaminants. Proceedings of the Twenty-ninth Arctic and Marine Oilspill Program (AMOP) Technical Seminar (Vancouver, BC, June 6-8, 2006). Vol. 1, Environment Canada – Emergencies Science and Technology Division, pp. 389-400.
• Greenberg, B.M. 2006. Development and field tests of a multi-process phytoremediation system for decontamination of soils. Canadian Reclamation, Spring/Summer, Issue 1, pp. 27-29.
• Greenberg, B.M., X.-D. Huang, J. Gurska, K.E. Gerhardt, M.A. Lampi, A. Khalid, D. Isherwood, P. Chang, W. Wang, H. Wang, D.G. Dixon and B.R. Glick. 2006. Development and successful field tests of a multi-process phytoremediation system for decontamination of persistent petroleum and organic contaminants in soils. In: CLRA 2006: Reclamation and Remediation: Policy and Practice. B. Tisch, K. Zimmerman, P. White, P. Beckett, L. Guenther, A. Macleod, S. Rowsome and C. Black, eds., Canadian Land Reclamation Association (CLRA), Calgary, AB, pp. 124-133.
• Greenberg, B.M., X.-D. Huang, D.G. Dixon and B.R. Glick. 2005. An integrated multi-process phytoremediation system (MPPS) for removal of persistent organic contaminants from soils. In: In Situ and On-Site Bioremediation, Paper K-08 (8 printed pages) in In Situ and On-Site Bioremediation – 2005. Proceedings of the Eighth International In Situ and On-Site Bioremediation Symposium (Baltimore, Maryland; June 6-9, 2005). B. Alleman and M. Kelly, eds., ISBN 1-57477-152-3, Batelle Press, Columbus, OH.
• Lampi, M., J. Gurska, K. McDonald, F. Xie, X.-D. Huang, D.G. Dixon and B.M. Greenberg. 2005. Photoinduced toxicity of PAHs to daphnia magna: UV-mediated effects and the toxicity of PAH photoproducts. Environ. Toxicol. Chem. 25: 1079-1087.

Books

• E.E. Little, B.M. Greenberg and A.J. DeLoney, eds. 1998. Environmental Toxicology and Risk Assessment. 7th Volume, ASTM STP 1333, American Society for Testing Materials, West Conshohocken, PA, 418 pp.
• B.M. Greenberg, R.N. Hull, M.H. Roberts, Jr. and R.W. Gensemer, eds., 2001. Environmental Toxicology and Risk Assessment. Science, Policy and Standardization – Implications for Environmental Decisions: 10th Volume, ASTM STP 1403, American Society for Testing Materials, West Conshohocken, PA, 358 pp.