Molecular control of sucrose utilization in Escherichia coli W, an efficient sucrose-utilizing strain

Sucrose is an industrially important carbon source for microbial fermentation. Sucrose utilization in Escherichia coli, however, is poorly understood, and most industrial strains cannot utilize sucrose. The roles of the chromosomally encoded sucrose catabolism (csc) genes in E. coli W were examined by knockout and overexpression experiments. At low sucrose concentrations, the csc genes are repressed and cells cannot grow. Removal of either the repressor protein (cscR) or the fructokinase (cscK) gene facilitated derepression. Furthermore, combinatorial knockout of cscR and cscK conferred an improved growth rate on low sucrose. The invertase (cscA) and sucrose transporter (cscB) genes are essential for sucrose catabolism in E. coli W, demonstrating that no other genes can provide sucrose transport or inversion activities. However, cscK is not essential for sucrose utilization. Fructose is excreted into the medium by the cscK-knockout strain in the presence of high sucrose, whereas at low sucrose (when carbon availability is limiting), fructose is utilized by the cell. Overexpression of cscA, cscAK, or cscAB could complement the W Delta cscRKAB knockout mutant or confer growth on a K-12 strain which could not naturally utilize sucrose. However, phenotypic stability and relatively good growth rates were observed in the K-12 strain only when overexpressing cscAB, and full growth rate complementation in W Delta cscRKA Balso required cscAB. Our understanding of sucrose utilization can be used to improve E. coli Wand engineer sucrose utilization in strains which do not naturally utilize sucrose, allowing substitution of sucrose for other, less desirable carbon sources in industrial fermentations

THE EFFECT OF ENTREPRENEURSHIP EDUCATION, AND SOCIAL ENVIRONMENT ON ENTREPRENEURIAL INTEREST WITH SELF-EFFICACY AS A MEDIATING VARIABLE

Entrepreneurial interest is still quite low in Indonesia because it is known that until now the number of entrepreneurs has not been able to reach the ideal number, SMK as a vocational school must always develop its quality to realize high-quality graduates in answering the needs of the industrial world and creating new entrepreneurs. This study uses a quantitative approach with Partial Least Squares structural equation modeling (PLS-SEM) to predict and confirm the hypotheses given. This study uses Google Forms for data collection on students of the Tourism Business Department of SMKN 1 Trowulan in Mojokerto Regency. Respondents in this study were 184 student respondents. The results showed that the Social Environment could not explain Self-efficacy or Entrepreneurial Interest. However, the Entrepreneurship Education variable can explain Self-efficacy and Entrepreneurial Interest. Furthermore, Entrepreneurship Education will have more influence on Entrepreneurial Interest, if strengthened by Self Efficacy as a mediator variable. The Social Environment will not have a greater influence on the Interest in Entrepreneurship, although strengthened with Self-efficacy as a mediator variabl

A Western Blot-based Investigation of the Yeast Secretory Pathway Designed for an Intermediate-Level Undergraduate Cell Biology Laboratory

The movement of newly synthesized proteins through the endomembrane system of eukaryotic cells, often referred to generally as the secretory pathway, is a topic covered in most intermediate-level undergraduate cell biology courses. An article previously published in this journal described a laboratory exercise in which yeast mutants defective in two distinct steps of protein secretion were differentiated using a genetic reporter designed specifically to identify defects in the first step of the pathway, the insertion of proteins into the endoplasmic reticulum (Vallen, 2002). We have developed two versions of a Western blotting assay that serves as a second way of distinguishing the two secretory mutants, which we pair with the genetic assay in a 3-wk laboratory module. A quiz administered before and after students participated in the lab activities revealed significant postlab gains in their understanding of the secretory pathway and experimental techniques used to study it. A second survey administered at the end of the lab module assessed student perceptions of the efficacy of the lab activities; the results of this survey indicated that the experiments were successful in meeting a set of educational goals defined by the instructor