Shawn Lewenza

Adjunct Professor, Department of Microbiology, Immunology and Infectious Diseases

Microbiology, Immunology & Infectious Diseases (MIID)
Member, Microbial Research Group
Address:  Room B871, Health Sciences Centre
                   3330 Hospital Drive N.W. , Calgary, AB T2N 4N1
Phone: (403) 220-4222
Email: slewenza@ucalgary.ca

Curriculum Vitae:
B.Sc. University of Manitoba 1995
Ph.D. University of Calgary 2000
Postdoctoral Fellow, University of British Columbia 2000-2004
Postdoctoral Fellow, Institute Pasteur, Paris, France 2004-2006
Westaim-ASRA Chair in Bacterial Biofilm Research 2006-2012    

Potential Graduate Supervisor

Funding: NSERC, Mitacs

Most of my research to date has been focussed on studying bacteria that are ubiquitous in the environment and also cause disease in individuals that are immunocompromised. We are specifically interested in the mechanisms of antibiotic resistance, immune evasion and how biofilms promote long-term survival. Pseudomonas aeruginosa was our model pathogen as it causes chronic lung infections in people with Cystic Fibrosis, and is a major cause of hospital-acquired, antibiotic resistant infections.

My current research interest is to design bacterial biosensor technologies for use in environmental monitoring and antibiotic discovery. We are currently funded to develop biosensors for the contaminants that accumulate in the tailings ponds in Northern Alberta.

Bitumen is recovered from surface mining of the Athabasca oilsands through a process of alkaline hot water extraction. The mining process generates oilsands process-affected water (OSPW), which is currently stored in vast tailings ponds (175 km2 area) on the banks of the Athabasca River. It is estimated that there will be 1 billion m3 of OSPW by 2025. OSPW contains water, sand, clay, silt, dissolved ions, heavy metals, unrecovered oil, and numerous organic compounds, many of which are toxic contaminants. There is no current, cost-effective, scalable technology available to remediate the organic contaminants in tailings ponds. There needs to be an effective, long-term, environmental monitoring strategy and ultimately, the OSPW stored in tailings ponds requires treatment before returning the water and land reclamation.

Naphthenic acids are among the most abundant and toxic compounds in the OSPW, present between 40-120 mg/L, yet can be toxic at 1-5 mg/ml. Naphthenic acids (NA) are a complex mixture of monocyclic, polycyclic, acyclic, alkyl-substituted carboxylic acids that have demonstrated toxicity against microbes, plankton, plants, fish and mammals. NA are naturally produced during the degradation of petroleum, and consist of simple compounds that are easily biodegraded, as well as more recalcitrant compounds with complex structures that are slow to degrade.

We are developing biosensors that detect naphthenic acids in OSPW, as an alternative to analytic chemistry methods for environmental monitoring. We are also interested in studying bacteria isolated from the oil sands process-affected water (OSPW) to understand the natural bioremediation capacity of organisms growing in this toxic environment. The goal of this research is to ultimately improve bioremediation and treatment of water the tailings ponds, which will ultimately be returned to the Athabasca River.

What are whole biosensors? Whole-cell bacterial biosensors are a proven technology that are capable of detecting and quantifying numerous analytes, which include various aromatic compounds (benzene, toluene, xylene, phenol, naphthalene), alkanes, solvents, sugars, heavy metals, and antibiotics, among others. Biosensors are engineered bacterial strains that can specifically detect low levels of small molecules and produce a simple, quantitative output proportional to the signal. This technology exploits a hallmark feature of bacteria, the ability to detect and respond to changing environmental conditions, by inducing the expression of relevant genes required for the response. The sensitivity for biosensors is commonly in the parts per million (ppm) range but can be sensitive to parts per billion (ppb). Biosensors express a genetic circuit comprised of a bacterial promoter responsive to a given compound that is fused to a transcriptional reporter. In addition to the reporter module just described, biosensors can also encode the sensing module that expresses the protein necessary for sensing the metabolites of interest.

The output reporter can be an enzyme that produces a colour change or a fluorescence signal, but we use the luxCDABE (bioluminescence) reporter for biosensor construction. The lux reporter is the ideal reporter of gene expression due to the dynamic range of light production, strong signal-noise ratios, the ability to measure real-time luminescence without the addition of substrates and the ease of high throughput experiments in 96 to 384-well format plates.