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Wei Zhang, Ph.D., Associate Professor of Biology, Division of Biology;  Associate Professor of Food Microbiology, National Center for Food Safety and Technology, Illinois Institute of Technology. 

Contact Information: 
Division of Biology  
Illinois Institute of Technology 
3101 S. Dearborn St. Chicago IL, 60616-3793

Institute for Food Safety and Health 
6502 S. Archer Rd, Bedford Park, IL 60501-1957 
Phone: (708) 563-2980 
Fax: (708) 563-1873
E-Mail address: zhangw@iit.edu

Research Interests:
My research focuses on using cutting-edge molecular biology and genomic approaches to study the ecology, stress response, and pathogenesis of bacterial pathogens that post major threats to food safety and public health.  My office and labs are located at the Institute for Food Safety and Health, Bedford Park, IL. My current research interests include:   

(i)  Pathogenesis of foodborne bacterial pathogens. One of my research topics is to study the intra-specific variations of bacterial pathogens that cause human infectious disease.  The model organism that I use is Listeria monocytogenes, a bacterium that contaminates dairy and Ready-to-Eat meat products and causes deadly infections (named “listeriosis) in pregnant women, young kids, and AIDS patients. The L. monocytogenes species is composed of 3 different genetic lineages (namely: I, II and III). Although all lineages possess virulence properties that make them pathogenic to human, two of these lineages (I and II) account for >95% of human infections; whereas lineage III is rarely implicated in human diseases for unknown reasons.  We speculate the existence of unknown genetic factors that regulate or contribute to the Listeria virulence.  We conducted comparative genomic analyses on 30 L. monocytogenes genomes. Using a novel Listeria pan-genome DNA microarray, we reported the core and dispensable genomes of this bacterial species and identified a number of new genes potentially related to its virulence. We are now in the process of functionally characterizing several of the newly identified genes to elucidate their roles in the Listeria intracellular pathogenicity.

(ii)  Bacterial stress physiology. Bacterial stress response is a key area that I am particularly interested in because virtually all biological questions that we try to address (such as bacterial survival in foods and pathogenicity in human) are fundamentally related to the physiology of bacterial pathogens under stress conditions. Our projects focus on understanding the stress response mechanisms that Listeria, Salmonella and E. coli use to proliferate in foods and persist in food processing facilities. We studied how Salmonella and E. coli respond to oxidative stress using whole-genome expression microarrays. We have identified over two hundred genes that were differentially regulated under the oxidative stress. These results shed new insights to the underlying mechanisms by which Salmonella and E. coli cope with the chlorine washes during the industry processing of fresh produce.  We are also studying the whole-genome expression profiles of Listeria under starvation stress as this bacterium transits from bacilli (rod shaped cells) to cocci (round shaped cells). Knowledge gained from this study will enable us to better understand how bacterial pathogens adapt to the food related environments. Therefore, we can develop more effective control strategies to minimize food contamination and prevent foodborne illness. 

(iii)  Comparative genomics.  Genomic analyses can provide comprehensive views to a specific biological question, and is the central theme of my research.  We used large-scale genomic approaches to analyze different types of foodborne bacterial pathogens.  For example, we used ultra-high-density DNA microarrays to resequence large E. coli O157 genomes (>5 million nucleotides per genome) at a very fine level (down to a single nucleotide).  The results from our study have proved to be extremely valuable for understanding the evolution of highly clonal bacterial pathogens. Ongoing projects in which we extensively use comparative genomics include the Listeria CGH project funded by USDA, the Salmonella/E. coli stress response project funded by FDA, and a newer project on genomic analysis of Clostridium botulinum.

(iv)  Bacterial epidemiology in the food system.  One of my research topics focuses on better understanding the ecology of bacterial pathogens in the food system. For instance, we developed a DNA sequence-based method for genotyping L. monocytogenes. Using this method, we were able to track the transmission routes of specific bacterial genotypes in the food supply chain.  We tested this method on diverse collections of food and environmental isolates as well as human clinical isolates. Other related research projects include:  a study of interactions of enteric pathogens (Salmonella and E. coli) with the plant carriers (such as lettuce and spinach) and potential horizontal gene transfers between enteric pathogens and indigenous plant and soil microflora; and a study of the effects of food matrices (such as beef) on the genome expression of E. coli O157:H7.

(v)  Rapid detection of bacterial pathogens and toxins in foods.  Food Science is a rather applied discipline. A practical aspect of my research is to develop new methods for rapid detection and identification of foodborne bacterial pathogens in foods. We worked with several biosensor research and development groups and assisted in developing new biosensors for rapid detection of infectious agents such as E. coli and Staphylococcus toxins in foods.  Our previous work also included developing multiplex assays for PCR serotyping, and the usage of proteomic approaches (such as MALDI-TOF mass spectrometry) for strain identification of E. coli, Salmonella and Shigella. We also develop microbiology  programs for method validation and detection of microbial contaminants including foodborne pathogens and select threat agents.