No description available.

Radiation sensitivity of E. coli O157:H7, non-O157 VTEC and Salmonella to low-dose ionizing irradiation was evaluated. Buffer-suspended E. coli O157 and non-O157 VTEC strains showed similar resistance to 300 Gy X-ray treatments, while Salmonella strains were more resistant. A dose of 1 kGy E-beam radiation reduced two groups of non-O157 E. coli mixtures and one E. coli O157:H7 group inoculated in meat by at least 4 log CFU/g. Salmonella showed only a <2 log CFU/g reduction. Sensory attributes of cooked ground beef patties were not affected (p >0.05) by irradiation. However, irradiated raw carcass muscles were more brown (p < 0.05) but displayed less intense off-aroma (p < 0.05) compared to the control during storage. Therefore, a 1 kGy treatment has the potential to improve microbiological safety with minimal effects on sensory properties of beef; it would be a suitable method for treating carcass trim before preparing ground beef.

No description available.

No description available.

Radiation sensitivity of E. coli O157:H7, non-O157 VTEC and Salmonella to low-dose ionizing irradiation was evaluated. Buffer-suspended E. coli O157 and non-O157 VTEC strains showed similar resistance to 300 Gy X-ray treatments, while Salmonella strains were more resistant. A dose of 1 kGy E-beam radiation reduced two groups of non-O157 E. coli mixtures and one E. coli O157:H7 group inoculated in meat by at least 4 log CFU/g. Salmonella showed only a <2 log CFU/g reduction. Sensory attributes of cooked ground beef patties were not affected (p >0.05) by irradiation. However, irradiated raw carcass muscles were more brown (p < 0.05) but displayed less intense off-aroma (p < 0.05) compared to the control during storage. Therefore, a 1 kGy treatment has the potential to improve microbiological safety with minimal effects on sensory properties of beef; it would be a suitable method for treating carcass trim before preparing ground beef.

No description available.

The discovery of penicillin ushered in the era of the mass use of antibiotics in clinical settings. Today the development of antibiotic resistance and lack of discoveries of new antibiotics have created a serious public health concern. Recently, new experimental tools, such as bacterial genome-wide deletion collections, have provided exciting new possibilities for studying biological networks in bacteria that could potentially also be exploited for antibiotic research. In this study, I used the Keio knockout collection of Escherichia coli (E.coli) strains, along with an in-house collection of hypomorphic alleles of essential genes, to study the effects of chemical perturbations by twenty-two antibiotics and four other chemicals on the biological pathways of E.coli. These experiments uncovered a set of mutants hypersensitive to drugs of different classes, information which could potentially be exploited for future antibiotic research. The results also shed light on how different classes of antibiotics behave with respect to their target pathways and the various functional modules with which they are associated.

The discovery of penicillin ushered in the era of the mass use of antibiotics in clinical settings. Today the development of antibiotic resistance and lack of discoveries of new antibiotics have created a serious public health concern. Recently, new experimental tools, such as bacterial genome-wide deletion collections, have provided exciting new possibilities for studying biological networks in bacteria that could potentially also be exploited for antibiotic research. In this study, I used the Keio knockout collection of Escherichia coli (E.coli) strains, along with an in-house collection of hypomorphic alleles of essential genes, to study the effects of chemical perturbations by twenty-two antibiotics and four other chemicals on the biological pathways of E.coli. These experiments uncovered a set of mutants hypersensitive to drugs of different classes, information which could potentially be exploited for future antibiotic research. The results also shed light on how different classes of antibiotics behave with respect to their target pathways and the various functional modules with which they are associated.

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 45-49). / v, 49 leaves, bound ill. 29 cm

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The recombinant expression of heterologous proteins in microorganisms, such Escherichia coli, is often improved by producing the protein of interest translationally linked to another, often unrelated, protein giving rise to a "fusion protein" construct. For many applications it is desirable or imperative to separate the extraneous material from the protein of interest. An increasingly popular approach to this task is the use of site-specific endoproteases 10 excise the protein product. A number of commercially available site-specific proteases exist, but many are not capable of generating an authentic N-terminus for the product, display unsatisfactory specificity leading to adventitious cleavage of the product, or they are unsuitable for an industrial process. Mutants of the serine protease a-Lytic protease have been shown to satisfy many of the criteria for an industrially suitable protease and have been applied to the cleavage of some important fusion proteins used in the production of members of the Insulin-like Growth Factor (IGF) family Lacking from these examples, however, is any viable proteolytic solution for the liberation of human IGF-I from fusion proteins. This has been primarily attributed to the Proline bearing N-terminal tripeptide sequence of this protein, which is known to be refractory to the activity of many site-specific proteases. It has been suggested that in the generation of two combinatorial mutant libraries of a-Lytic protease, the preference for amino acids C-terminal to the cleavage site may have been altered. It is the purpose of this work to first determine if such an alteration has been made in any of the mutants so as to allow cleavage immediately before the N-terminus of human IGF-1, and then to task the lead mutant(s) to the cleavage of the full-length fusion protein. All members of the two mutant libraries were cultured and their activity confirmed and quantified against a generic B-casein substrate in a high-throughput assay. A second high-throughput technique was then employed to query the mutant proteases for their ability to catalyse proteolysis at the required sequence in a peptide model. Finding that many mutants appeared successful at this task, the findings were verified on a longer peptide model of the cleavage site. Initially the yields achieved by cleavage of the full-length IGF-1 fusion protein by a lead candidate mutant a-Lytic protease were not sufficient to satisfy the requirements of an industrial process, despite alteration of the reaction conditions. However, the insight gained from these reactions could be applied to the redesign of the protein structure around the intended site of cleavage, significantly improving site-specific proteolysis. The IGF-1 generated by this cleavage has been shown to be bioequivalent to commercial reference standard to cultured mammalian cells and the yield of this process is approximately 5-fold improved over the existing cleavage system. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1325381 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008