Bruce M. Greenberg

• Ecology and Environmental Biology
• Physiology, Cell and Developmental Biology
• Molecular Genetics

Environmental Chemistry and Biology

Phytoremediation of xenobiotic contamination; ultraviolet radiation mediated photochemistry and photobiology. His 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. He and his group 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.

Greenberg and his group 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. He is now adapting the PEPS for remediation of urban brownfield sites.

Internationally, he has successfully deployed his 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). He believes 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 ed 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).

Professor Greenberg teaches both undergraduate and graduate courses. Course offerings have included

• BIOL 331 Advanced Cell Biology
• BIOL 354 Environmental Toxicology
• BIOL 439 Biochemistry of Natural Products
• BIOL 499 Senior Honours Research Project
• BIOL 621 Phytoremediation
• BIOL 622 Selected Topics in Plant Physiology - Phytoremediation
• BIOL 670 Photobiology

Recent publications include

• Greenberg, BM, KE Gerhardt, S Liddycoat, P Gerwing and E Murray (2015) Phytoremediation of PHC impacted soils – Use of PGPR-Enhanced Phytoremediation Systems to meet generic Tier 1 remediation criteria. Canadian Reclamation, 15(1): 40-47.

• Gurska, J, BR Glick and BM Greenberg (2015) Gene expression of Secale cereale (fall rye) grown in petroleum hydrocarbon (PHC) impacted soil with and without plant growth promoting rhizobacteria (PGPR), Pseudomonas putida. Water Air Soil Poll., 226:308, doi:10.1007/s11270-015-2471-x.
• Chang, P, KE Gerhardt, X-D Huang, X-M Yu, BR Glick, PD Gerwing and BM Greenberg (2014) Plant growth-promoting bacteria facilitate the growth of barley and oats in salt-impacted soil: Implications for phytoremediation of saline soils. Int. J. Phytorem. 16: 1133-1147.

• Smith, BA, BM Greenberg and GL Stephenson (2012) Bioavailability of copper and zinc in mining soils. Arch. Environ. Contam. Toxicol. 62: 1-12 (Published on-line 19 May 2011. DOI 10.1007/s00244-011-9682-y).

• Emerald Award for Phytoremediation of Petroleum Hydrocarbons, 21st Annual Emerald Awards (2012)
• Braggin' Dragon Award of Innovation for Phytoremediation Technology, Dragon's Lair, EnerCan West (2012)
• C.D. Nelson Award, Canadian Society of Plant Physiologists (1996)
• Environmental Research and Technology Development Award, Ontario Ministry of Environment and Energy (1993)
• National Research Service Award, National Institutes of Health Fellow (1985-88)
• University of Colorado Doctoral Fellowship (1982-83)

• Cross-appointed to Chemistry
• The Water Institute, Member
• President, Waterloo Environmental Biotechnology Inc.
• Adjunct Professor, Department of Environmental Biology, University of Guelph

• American Chemical Society
• American Society of Photobiology
• American Society of Plant Physiologists
• American Society of Testing and Materials
• Canadian Society of Plant Physiologists
• Society of Environmental Toxicologists and Chemists
• Canadian Land Reclamation Association
• American Society of Plant Biologists
• Ontario Environmental Industry Association (ONEIA)

The following news stories have featured Professor Greenberg's research:

• 07/02/2012 – 26/06/2012 Expert Witness activities         
• 04/2010 The grass is greener… (New Technology Magazine)   
• 04/2010 Phytoremediation (Air, Water and Land)
• 11/2009  Spotlight on Technology (KW Record Special)

1985 PhD University of Colorado, Boulder

1980 BSc Chemistry, University of California, Berkeley