TY - JOUR TI - Rroles of plant defense response and bacterial surface polysaccharides in survival of human enteric pathogens Escherichia coli O157:H7 and Escherichia coli O104:H4 on plants DO - https://doi.org/doi:10.7282/T37D2Z7W PY - 2017 AB - Human enteric pathogens are associated with numerous outbreaks by consumption of contaminated fresh produce, which indicates that plants or vegetable crops can be potential hosts for pathogens. In order to enhance safety of fresh produce, it is important to understand the interactions between human enteric pathogens and plants. However, little information is available about the behavior of human enteric pathogens on plants, such as mechanisms of survival and persistence. In this study, we investigated survival and persistence of Escherichia coli O157:H7 and O104:H4 strains on Arabidopsis thaliana and romaine lettuce, as well as production of capsular polysaccharide (CPS) and induction of plant defense response. Colonization study with E. coli O157:H7 86-24 wild-type strain and its isogenic mutants of surface polysaccharides showed that colanic acid-deficient and lipopolysaccharide (LPS)-deficient mutants significantly less survived on Arabidopsis plant and lettuce on day 1 and 5 post-inoculation, compared to the wild-type. The two mutants of colanic acid and LPS induced 2-fold greater PR1 gene expression and produced significantly lower amount of CPS compared to wild-type strain (P < 0.05). The results may suggest that structures of colanic acid and LPS of E. coli O157:H7 influence the plant defense response, thereby resulting in different survival and colonization on plants. To investigate fitness of an emerging Shiga toxin-producing E. coli (STEC), colonization of E. coli O104:H4 strains on plants were compared with of that of E. coli O157:H7 strains. Results showed that E. coli O104:H4 strains (RG1, C3493, and LpfA) significantly survived better than E. coli O157:H7 strains (7386 and sakai) on Arabidopsis plant and lettuce at day 5, with greater production of CPS and lower expression of PR1 gene (P < 0.05). These results indicate that different level of plant defense response and CPS production may have an impact on survival or fitness of E. coli O104:H4 and O157:H7 on plants. In order to develop control strategies in crop cultivation environments, it is essential to learn about the behavior of human enteric pathogens on plants, particularly factors influencing the ability of pathogen to overcome plant host immunity. The present study provides better understanding of roles of plant defense response and surface polysaccharides on the molecular interactions between human pathogens and plants. Interestingly, the similar trend of bacterial survival/persistence between Arabidopsis (model plant) and lettuce (plant crop) may suggest a potential use of Arabidopsis as an appropriate model plant for studying the mechanisms of plant responses to human enteric pathogens on leafy vegetables. This study also provides an insight into potential roles of CPS in the survival of human enteric pathogens. KW - Food Science KW - Escherichia coli LA - eng ER -