No description available.

No description available.

Although bacteriophage was discovered some twenty-odd years ago, little is yet known of its real nature. It has been investigated extensively, but is still best known by its notion on micro-organisms susceptible to it. When a small amount of bacteriophage is added to a young culture of susceptible organisms it brings about their dissolution, or lysis within a few hours. The time required for this phenomenon is variable, but the importance of the result is readily recognized and was immediately of great interest to medical men. At first it appeared that in this substance had been found a “cure-all” for all bacterial diseases, and it has been from the therapeutic as well as the physico-chemical standpoints that it has been investigated. The subsequent work with this material did not bear out the glowing reports of D’Herelle. The results from its therapeutic use were so inconsistent that it was not long before its use had been generally discarded. Many explanations were offered for the variable clinical results. Although D’Herelle (8) states that the body fluids do not inactivate phage, Colbin (5 & 6) reports to the contrary. The idea of greater specificity of the phage to the susceptible organism has also been advanced, but very little work has been done to demonstrate the degree of specificity that does exist. In this work, the author has assumed that a specificity comparable to serological specificities does not exist and has endeavored to show this with different strains and species of the gene Escherichia. The proof of a species or strain specificity in this germ would warrant the hypothesis that such specificity does also exist in other pathogenic genes and thus a better explanation for the therapeutic inconsistencies resulting from the use of commercially prepared phages might be advanced. / Master of Science

No description available.

Bacteriophage (phage), virus of bacteria, has been proposed as a mean to inactivate bacteria that are pathogens of humans. Applied prophylatically to food, phage might decrease the numbers of potential pathogens we ingest. Much active research on using the phages of bacteria to control Gram negative foodborne pathogens are described in the literatures, but comparatively little research describes the phages of Gram positive bacteria and their use as biocontrol agents on food. In this work, previous undescribed phages, able to infect Bacillus cereus and Listeria monocytogenes, were isolated from soil and ruminants faecal material, respectively. As the first step in assessing their potential as biocontrol agents, the isolated phages were purified, concentrated and characterised (albeit to different degrees). The Bacillus phages had a narrow host range while the Listeria phages had a broad host range. Listeria phages also infected L. monocytogenes 2000/47, a strain which recurs in New Zealand clinical cases. Both Bacillus and Listeria phages appeared to be of the Myoviridae family judging by their structure in electron micrographs. The Bacillus FWLBc1 and FWLBc2 phages were lytic phages with a latent period of 106 and 102 min at 37°C, and an average burst size of 322 and 300 phages per infected cell, respectively. Moreover, they both had genomes of approximately 134 kb. All newly isolated and characterized phages were chloroform resistant and survived storage better at 4°C than at room or freezing temperatures. Bacillus phages significantly reduced the bacterial population in mashed potatoes within 24 h at room temperature, when applied at a phage to host ratio of 1000. Listeria phages rapidly inactivated the host population to a low optical density. The findings of this thesis will add to the current knowledge of phages in the context of various environmental conditions for different bacteria and will demonstrate the potential of phages as food safety biocontrol agents.

Call number: LD2668 .T4 1959 P36

Restriction enzyme, molecular cloning and DNA annealing techniques have been used to study mRNA and DNA coding for the embryonic feather keratins of the chicken and the DNA genomes of coliphages 186 and P2. The coliphage DNAs were used to develop the techniques for application to the keratin system which awaited the availability of appropriate bio - hazard containment facilities before being undertaken. The following results were obtained. 1. Restriction endonuclease cleavage of chick DNA with BamHI, BgïII, EcoRI, or HindIII, fractionation on agarose gels, immobilization on nitrocellulose filters and annealing to DNA complementary to purified 12S mRNA isolated from the developing embryonic feather and coding for embryonic feather keratins, yielded a complex pattern of major and minor bands. These patterns consisted of 4 - 6 major bands and many minor bands. No simple repeat length could be deduced from these patterns, suggesting that keratin - coding DNA is heterogeneous in coding sequences, non - coding sequences or both. 2. Keratin gene expression was shown to be independent of DNA rearrangement, as the complex pattern of restriction fragments was identical in DNA isolated from germ - line tissue ( sperm ) the differentiated feather tissue and somatic tissue not synthesizing keratins ( erythrocytes ). Keratin gene expression must therefore involve the activation of pre - existing control regions in the DNA. 3. The purified 12S mRNA coding for feather keratin was transcribed into double - stranded DNA and individual species isolated by molecular cloning in E. coli. Sequence variation between species was confirmed by restriction enzyme analysis. 4. Preliminary analysis of the cloned species revealed the existence of two distinct groups of species comprising 12S mRNA : Group I ( the more abundant group ) and Group II ( the less abundant ). The fact that filter - bound DNA of individual Group I species bound more 12s cDNA than equal amounts of Group II species DNA and that pure Group I species and total 12S mRNA sequences ( coding for keratins in cell - free translation systems ) annealed to exactly the same complex set of EcoRI, HindIII, or BgïII restricted chick DNA fragments, compels the conclusion that Group I species represent true keratin coding sequences. Group II species annealed to restricted chick DNA fragments which were totally different to those annealing, to either Group I species or total 12S mRNA sequences. Different Group II species appeared to anneal to certain common fragments, suggesting that this less abundant group was comprised of a family of sequence related species and were not simply contaminating mRNA species coding for ' housekeeping ' functions. Their exact nature is at present, however, uncertain. 5. Group I species, the presumptive keratin - coding species, are members of a family of homologous species present in the chick genome. This is demonstrated by the fact that the two Group I species which have been examined so far, shown to be non - identical by restriction analysis, and total 12S mRNA sequences from which they were derived, annealed to the same set of between 20 and 30 BglII, HindIII or EcoRI restricted chick DNA fragments under annealing and washing conditions of low stringency, ( high salt ). Under stringent ( low salt ) washing conditions, however, all except between 1 and 3 of the duplexes formed by these fragments and the Group I species were differentially lost from the filter, indicating that the majority of duplexes were mis - matched and therefore that these multiple copies were homologous and not identical. In addition the two non - identical Group I species annealed to EcoRI generated chick DNA fragments of different sizes under the stringent ( low salt ) washing conditions, demonstrating that differences must exist in the sequence of adjacent non - coding and / or intervening sequences ( should they exist ) for these two species. 6. Although the two Group I species discussed above annealed to different EcoRI generated chick DNA fragments under the stringent ( low salt ) washing conditions, they both annealed under these conditions to a HindIII generated chick DNA fragment of size 3.0 kb. Assuming that this is a single fragment and not two fragments co - electrophoresing by chance, sequences identical to or with very close homology to both of these species lie on the same fragment and are therefore linked in the genome. The exact nature of this linkage and of the extent of gene clustering, should it exist, was not determined. 7. Restriction cleavage maps of coliphages 186 and P2 were determined for the enzymes BamHI, BglII, EcoRI, HindIII, PstI, SaïI, XbaI, and XhoI. These maps were used to analyse four insertion or deletion mutants affecting the major control region of 186. 186ins2 and 186ins3 were shown to be insertions of an IS3 element in the cI. gene and int gene respectively. 186dell and 186del2 were shown to carry the same deletion affecting the cI gene, but 186del2 carried a cryptic insert in the repressor binding site ( operator ). / Thesis (Ph.D.)--Department of Biochemistry, 1979.

Includes bibliography / 219 leaves, [22] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1987

Bibliography: leaves 94-104

Graduation date: 2000