Effect of Genetically Modifying the Lactococcal Proteolytic System on Ripening and Flavor Development in Cheddar Cheese

Three batches of six Cheddar cheeses were manufactured by using the following lactococcal strains: (i) UC317 as a control; (ii) JL3601, a proteinase-negative derivative of UC317 transformed with high-copy-number plasmid pCI3601 containing the cloned proteinase gene complex from UC317; (iii) AM312, a proteinase-negative derivative of UC317 transformed with plasmid pMG36enpr containing the neutral proteinase gene from Bacillus subtilis; (iv) AC322, JL3601 transformed with pMG36enpr; (v) AC311, UC317 transformed with plasmid pNZ1120, which contains the aminopeptidase N (pepN) gene from Lactococcus lactis subsp. lactis MG1363; and (vi) AC321, JL3601 transformed with pNZ1120. Organoleptic and chemical analyses indicated that (i) the control cheeses, which were made with UC317, were of the highest quality; (ii) cheeses made with strains harboring pCI3601 in addition to either pMG36enpr (AC322) or pNZ1120 (AC321) did not ripen in a significantly different manner than cheeses made with AM312 (containing only pMG36enpr) or AC311 (containing only pNZ1120), respectively; (iii) cheeses made with strains that overproduce pepN did not have improved body, texture, and flavor characteristics; and (iv) cheeses made with strains harboring the neutral proteinase from B. subtilis (AM312 and AC322) underwent greatly accelerated proteolysis.     

Horizontal spread of an altered penicillin-binding protein 2B gene between Streptococcus pneumoniae and Streptococcus oralis

Abstract The region encoding the transpeptidase domain of the penicillin-binding protein 2B (PBP 2B) gene of two penicillin-resistant clinical isolates of Streptococcus oralis was > 99.6% identical in nucleotide sequence to that of a penicillin-resistant serotype 6 isolate of Streptococcus pneumoniae . The downstream 849 base pairs of these genes were identical. Analysis of the data indicates that the PBP gene has probably been transferred from S. pneumoniae into S. oralis , rather than vice versa, and shows that one region of this resistance gene has been distributed horizontally both within S. pneumoniae and into two different viridans group streptococci.     

Stimulation of guanylate cyclase activity and reduction of adenylate cyclase activity by granulocyte-macrophage colony-stimulating factor in human blood neutrophils

Human neutrophils were incubated with granulocyte-macrophage (GM)-CSF and examined for changes in second messenger systems. Twofold increases in cGMP but not cAMP were measured after 5 to 20 min with 100 U/ml GM-CSF. Guanylate cyclase activities in membrane and cytosol fractions were increased to the same extent whether measured in the presence of Mg2+ or Mn2+, or in the cytosol with Mg2+ + N-methyl-N'-nitro-N-nitroso-guanidine. Kinetic studies of the cytosol enzyme showed no changes in the Km values for Mg2+ and Mn2+dependent guanylate cyclase activities (0.91 and 0.022 mM, respectively), whereas Vm values were increased after treating intact cells with GM-CSF. Two peaks of guanylate cyclase activity were observed, one at 10 and another at 60 min after adding 100 U/ml GM-CSF, whereas only one peak at 5 min occurred with 1 U/ml. Adenylate cyclase activity was reduced by nearly 50% after adding 100 U/ml GM-CSF for 10 to 30 min. These effects were also seen in the presence of several hormonal and nonhormonal adenylate cyclase stimulators. In contrast, small increases in adenylate cyclase activity occurred after adding 1 U/ml GM-CSF. In experiments to examine the pathway of guanylate cyclase activation by GM-CSF, we observed no changes in inositol phosphates, intracellular calcium ion, or cytosolic protein kinase C. The augmentation of chemotactic peptide-induced superoxide production by GM-CSF concentrations, may be related to the effects of the higher levels of GM-CSF to stimulate late increases in guanylate cyclase or decreases in adenylate cyclase.     

Microbial Exposure Assessment of Waterborne Pathogens

The large number of waterborne illnesses in Ireland and worldwide has highlighted the need to enhance strategies that minimize human exposure to pathogens in drinking water supplies. Waterborne pathogens of public concern together with relevant national and international legislation are reviewed in this study. Cryptosporidium species and pathogenic Escherichia coli are among pathogens of primary concern. The organisms originate from the gastrointestinal tract of animals and humans. They may be associated with persistent contamination of water sources, survive for long periods in the environment, and, in particular in the case of Cryptosporidium species, may survive in chlorinated water supplies. Prevention of waterborne infection should emphasize source protection in addition to water treatment. Risk assessment models can play an important role in protecting natural water systems from contamination with these pathogens. Qualitative approaches can provide an effective means of assessing risks with minimum resources and limited data; however, they lack the precision and predictive ability of fully quantitative approaches. Thirteen quantitative simulation models that could potentially be used for modeling bacterial pollutants in agricultural watersheds have been assessed in this study. No one model suits all modeling criteria. Pathogen predictions have proved variable and no model was capable of accounting for all geological and hydrological factors in addition to modeling the physical transport of bacteria in surface runoff. This assessment summarizes commonly used models and their capacity to model water pollution while also providing a good reference point for the microbial risk assessment of waterborne pathogens.     

The <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis> Type III Secretion Systems manipulate host cell MAPK for critical steps in pathogenesis

Background  

Vibrio parahaemolyticus is a food-borne pathogen causing inflammation of the gastrointestinal epithelium. Pathogenic strains of this bacterium possess two Type III Secretion Systems (TTSS) that deliver effector proteins into host cells. In order to better understand human host cell responses to V. parahaemolyticus, the modulation of Mitogen Activated Protein Kinase (MAPK) activation in epithelial cells by an O3:K6 clinical isolate, RIMD2210633, was investigated. The importance of MAPK activation for the ability of the bacterium to be cytotoxic and to induce secretion of Interleukin-8 (IL-8) was determined.