LU-CAEHS Research Seminar

“Food Safety and Water Quality: Focusing on Raw Vegetables and Environmental Water”

In the United States, approximately 45% of foodborne illness outbreaks result from consuming pathogen-contaminated raw vegetables, such as lettuce and sprouts. In severe cases, pathogens like E. coli O157:H7 can enter (internalize) within plant tissues, making them resistant to post-harvest washing and sanitation. Our study investigated the potential of beneficial plant-associated bacteria, specifically Pseudomonas spp. and Bacillus subtilis, to control E. coli O157 internalization in romaine lettuce and mung bean sprouts. Notably, B. subtilis effectively reduced pathogen internalization in mung bean sprouts. Additionally, E. coli internalization in romaine lettuce was linked to the bacterial PhoQ/PhoP stress response system, which regulates adaptation to environmental stressors, including Mg²⁺ and Ca²⁺. Preliminary data suggest that increasing Mg²⁺ levels in the cultivation system may help mitigate the pathogen internalization in romaine lettuce.

Waterborne illnesses affect approximately 7.2 million Americans annually, with fecal pollution being a primary cause. Identifying fecal contamination sources is crucial for effective water quality restoration because the sources must be identified before steps can be taken to remove or mitigate them. We have developed several DNA- and fecal bacteria-based methods to trace fecal pollution from human and poultry sources, with ongoing efforts to enhance accuracy and expand detection to other host sources.

Presented by Dr. Guolu Zheng, Professor of Microbiology.

Dr. Guolu Zheng earned his Ph.D from the University of Arkansas, Fayetteville. Before joining Lincoln University in 2009, he served as a research assistant professor at the University of Rochester, New York, and later at the University of Missouri. His research focuses on food safety and water quality, with recent expansions into plant health.