Exotoxin A production in Pseudomonas aeruginosa is regulated positively or negatively by several genes. Two such regulatory genes, ptxR and ptxS, which are divergently transcribed from each other, have been described previously. While computer analysis suggested that the ptxR-ptxS intergenic region contains potential binding sites for several regulatory proteins, the mechanism that regulates the expression of either ptxR or ptxS in P. aeruginosa is not known. The presence of a P. aeruginosa protein complex that specifically binds to a segment within this region was determined. In this study the binding region was localized to a 150 bp fragment of the intergenic region and the proteins that constitute the binding complex were characterized as P. aeruginosa HU and MvaT. Recombinant MvaT was purified as a fusion protein (MAL-MvaT) and shown to specifically bind to the ptxR-ptxS intergenic region. A PAO1 isogenic mutant defective in mvaT, PAODmvaT, was constructed and characterized. The lysate of PAODmvaT failed to bind to the 150 bp probe. The effect of mvaT on ptxS and ptxR expression was examined using real-time PCR experiments. The expression of ptxS was lower in PAODmvaT than in PAO1, but no difference was detected in ptxR expression. These results suggest that MvaT positively regulates ptxS expression by binding specifically to the ptxS upstream region.
Microwaves have been shown to cause thermal as well as nonthermal destruction of pathogens such as Salmonella, which can be found in shell eggs. The objective of this study was to determine if using microwave technology would cause detrimental quality effects in shell eggs. Treatments included control (no treatment) and microwave-treated (20 s) shell eggs. There were no differences in mineral content, fatty acid profile, Haugh units, broken-out score, yolk index, emulsion stability, pH of whole egg, and foaming capacity between 2 treatments (P >or= 0.05). At 0 and 30 d, there were no noticeable differences in H(2)O activity between 2 treatments. The foaming stability and albumen thermocoagulation of microwave-treated eggs were significantly higher than control eggs (P or= 0.05). Therefore, microwave technology can be applied to shell eggs without causing detrimental effects to quality.
This study was designed to provide updated information on the separable components, cooking yields, and proximate composition of retail cuts from the beef chuck. Additionally, the impact the United States Department of Agriculture (USDA) Quality and Yield Grade may have on such factors was investigated. Ultimately, these data will be used in the USDA - Nutrient Data Laboratory's (NDL) National Nutrient Database for Standard Reference (SR). To represent the current United States beef supply, seventy-two carcasses were selected from six regions of the country based on USDA Yield Grade, USDA Quality Grade, gender, and genetic type. Whole beef chuck primals from selected carcasses were shipped to three university laboratories for subsequent retail cut fabrication, raw and cooked cut dissection, and proximate analyses. The incorporation of these data into the SR will improve dietary education, product labeling, and other applications both domestically and abroad, thus emphasizing the importance of accurate and relevant beef nutrient data.
Since nutrient composition of pork has changed over the past two decades, a collaborative study was conducted by scientists at the US Department of Agriculture (USDA), Texas Tech University and the National Pork Board to determine current nutrient values. The purpose was to obtain analytical nutrient data for three highly consumed fresh pork products in the USDA National Nutrient Database for Standard Reference (SR) and to compare the results to data obtained in 1992. Bone-in baby back ribs (BKR), boneless sirloin roast (SRB), and bone-in blade chops (BCB) were purchased from 12 retail outlets using a nationwide sampling plan developed for . Nutrient values for proximate, cholesterol, and minerals were determined by commercial laboratories using validated methodology including quality control procedures. The 1992 data used for comparison were derived from analyses of samples of raw fresh pork retail cuts which were obtained from supermarkets in 15 cities across the US in a nation-wide market basket study. Nutrient values from 1992 and 2010 for equivalent cuts were statistically evaluated using a paired two-tailed T-test (critical value p<0.05). Comparing 2010 values to 1992 values, moisture was significantly higher (p<0.001) while total fat was lower (p<0.001) in all three cuts. Cholesterol was significantly less in two of the three cuts. Sodium values for 2010 were higher in all three cuts by 7-24% but still below 90 mg/100 g. Phosphorus was higher (p<0.05) in 2010 whereas iron was lower (p<0.001). Values for potassium, calcium, and zinc varied between the two data sets. This research updates the values in SR and provides current and accurate data for use in nutrition monitoring and policy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.