BackgroundA previous study identified a Yersinia enterocolitica transposon mutant, GY448, that was unable to export the flagellar type three secretion system (T3SS)-dependent phospholipase, YplA. This strain was also deficient for motility and unable to form colonies on Lauria-Bertani agar medium. Preliminary analysis suggested it carried a mutation in csrA. CsrA in Escherichia coli is an RNA-binding protein that is involved in specific post-transcriptional regulation of a myriad of physiological activities. This study investigated how CsrA affects expression of the flagellar regulatory cascade that controls YplA export and motility. It also explored the effect of csrA mutation on Y. enterocolitica in response to conditions that cue physiological changes important for growth in environments found both in nature and the laboratory.ResultsThe precise location of the transposon insertion in GMY448 was mapped within csrA. Genetic complementation restored disruptions in motility and the YplA export phenotype (Yex), which confirmed this mutation disrupted CsrA function. Mutation of csrA affected expression of yplA and flagellar genes involved in flagellar T3SS dependent export and motility by altering expression of the master regulators flhDC. Mutation of csrA also resulted in increased sensitivity of Y. enterocolitica to various osmolytes, temperatures and antibiotics.ConclusionsThe results of this study reveal unique aspects of how CsrA functions in Y. enterocolitica to control its physiology. This provides perspective on how the Csr system is susceptible to adaptation to particular environments and bacterial lifestyles.
Cambodian foods are increasingly consumed outside Southeast Asia, yet are the subject of remarkably few reports. The Khmer culture and culinary traditions of Cambodian people, both historical and contemporary, depend most heavily on the fermented fish product prohok ("Image missing") as an essential ingredient in a wide variety of dishes. The aim of this report is to better understand the traditions, production methods, and uses of prohok as well as the retention of this essential flavoring and nutritional component of Khmer cuisine. The reported findings include how fish preservation developed to accommodate Cambodia's unique naturally occurring hydrological phenomena and has influenced the ethnic identity and social structure of Khmer people. Commercial and home production of prohok is observed to have socioeconomic and nutritional impact on people. The uses of prohok in main dishes, sauces, soups, and side dishes are explored. Furthermore, this report investigates and reviews the underlying microbiology and chemistry that takes place during traditional fermentations of fish to produce prohok. This foundational knowledge serves as a basis for additional scientific studies to further investigate prohok fermentations with the goal to better understand factors that contribute to the unique regional variation of aromas, textures, and flavors produced by traditional practitioners and beloved by Khmer people.
Although many educators now recognize the value of problem-based learning and experiential learning, undergraduate-level food science courses that reflect these pedagogical approaches are still relatively novel, especially in East and Southeast Asia. Leveraging existing partnerships with farmers in Vietnam, a food science course for students at Nong Lam Univ. was designed and taught. The aim was to give students the opportunity to work in small groups and conduct evidence-based research with farmers, apply food science principles, and develop Success Skills, including the ability to think critically and communicate clearly. Drawing on the experience of 2 student groups, this exploratory study describes what students learned from the process of conducting research. In one group, students learned to work through and resolve the challenge of initial disagreement and misunderstanding with farmers and ultimately carried out a project that aligned with the students' research interests and farmers' needs. Another group of students learned to consider the financial limitations of farmers when attempting to develop solutions for problems and ultimately worked with farmers to address a different problem that was less financially taxing. It is important to note the challenges of planning and teaching a course in which instructors are not able to predict exactly what students will learn or experience. This is largely dependent on each student's prior knowledge, experiences, and interests; yet this study demonstrates the transformative potential of teaching a research-based food science course that gives students authentic opportunities to identify and address real-world challenges.
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