Escherichia coli O157:H7 is responsible for a human toxico-infection that can lead to severe complications such as hemolytic uremic syndrome. Inside the intestine, E. coli O157:H7 forms typical attaching-effacing lesions and produces Shiga toxins. The genes that are responsible for these lesions are located in a pathogenicity island called the locus of enterocyte effacement (LEE). LEE gene expression is influenced by quorum sensing through the luxS system. In this study, the effect of glucose on the expression of several genes from LEE, on the expression of Shiga toxin genes, and on the expression of luxS was assessed with real-time, reverse transcription PCR. All concentrations of glucose (from 0.1 to 1%) were able to down-regulate genes from the LEE operon. A slight down-regulation of genes implicated in Shiga toxin expression was also observed but was significant for low doses of glucose (0.1 to 0.5%) only. A slight but significant increase in luxS expression was observed with 1% glucose. This confirms that in addition to quorum sensing, the presence or absence of nutrients such as glucose has an impact on the down- or upregulation of LEE-encoded virulence genes by the bacterium. The influence of glucose on the virulence of E. coli O157:H7 has received little attention, and these results suggest that glucose can have an important effect on the virulence of E. coli O157:H7.

Results suggest that diarylheptanoids are the active principles that provide protection against t-BHP-induced injury. Their ability to maintain intracellular glutathione content is the main mechanisms underlying the protective action.

A traditional classroom usually focuses on concepts from a specific discipline. However, solving complex real-world problems requires integration and application of knowledge from various fields. Here, we describe a 4-hr undergraduate-level laboratory exercise that utilizes concepts of extraction and biological property, bridging between chemistry and microbiology courses. In the first half of this exercise, students performed hydrodistillation to extract essential oil from a locally available herb, lemongrass (Cymbopogon citratus, Stapf). In the second half, students investigated the potential antimicrobial activity of the extracted oil against various microorganisms using the Kirby-Bauer disk diffusion method. Students also developed their own experimental questions based on the extracted oil and the antimicrobial testing technique. Self-assessment questionnaire shows students' appreciation of the experiments and substantial learning gains in the extraction process, properties of the extracts, and antimicrobial activity testing. This laboratory exercise prompts students to formulate their own experimental questions and engages students in interdisciplinary experimentation.

No abstract