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.

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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.

The effect of the stage and number of lactations on the technological properties and cheese‐making capacity was studied in Murciano‐Granadina goat's milk. Controls were done every month to evaluate the evolution of chemical composition and the values of the clotting properties which define the milk quality with regards to rennet curdling. The influence of the month of kidding was also evaluated. The average composition of the milk in the two kidding periods considered was as follows: fat 5.05% and 5.31%; protein 3.68% and 3.58%; casein 2.80% and 2.66%; lactose 4.71% and 4.68%, and dry matter 14.29% and 14.45%. No significant differences were found in the chemical composition due to the stage and lactation number; however, higher values of the protein fractions were determined in the first kidding period than in the second one. We determined that a higher casein concentration was associated with a lower milk clotting time and higher rate of firmness. We also found a highly significant (P < 0.001) correlation between titration acidity values and casein content (0.551). No significant differences, however, were found in cheese composition between kidding periods. © 1999 Society of Chemical Industry

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.

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