Genetic studies on collagenolytic achromobacter strains and their bacteriophages
- Authors: Thomson, Jennifer Ann
- Date: 1974
- Subjects: Bacteriophages -- Genetics Bacterial genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4246 , http://hdl.handle.net/10962/d1007291
- Description: From Summary: A survey of collagenolytic aerobic bacteria from cured hides yielded three strains of Bacillus and eight of Achromobacter which degraded collagen at 0.4 M NaCl. Achromobacter sp. 2 was chosen for genetic studies due to its high collagenolytic activity and the lack of genetic information on Achromobacter. Four temperate bacteriophages specific for Achromobacter sp. 2 were isolated and their relationships studied. The phages caused lysogenic conversion resulting in the inability of lysogens to adsorb phage. Achromobacter sp. 2 was shown to be a cryptic lysogen as it was not immune to superinfection but had a very low rate of spontaneous induction which could be increased with mutagens. It is proposed that the cryptic lysogeny of this strain is maintained by a defective excision mechanism and the mode of prophage integration in the host chromosome. DNA extracted from phage α3a was used to transfect spheroplasts. The optimal conditions for the development of competence for transfection were determined. The presence of nuclease-attack on phage DNA under conditions of prolonged incubation of DNA and spheroplasts was proposed. A method for extracting Achromobacter DNA was devised which yielded purified, undegraded DNA, but it was not possible to transform Achromobacter sp. 2 with this DNA. The a phages were used to transduce a number of genetic markers into Achromobacter auxotrophs. The transduct ants had the ability to release the cryptic α3 prophage at a high rate while maintaining their sensitivity to homologous phage infection. It is proposed that this is due to complementation between the cryptic prophage and the residual phage functions in the transducing particles. The transductants segregated auxotrophs with a probability of 10⁻³ per cell per generation. It appears that an unusual system of generalised transduction is operating whereby the transducing particles contain both phage and bacterial DNA which is incorporated into the recipient genome by a single recombination event yielding unstable transductants. In a study on induction of Escherichia coli (λ), carcinogenic nitrosamines were shown to be inducers of phage development. This provides a screening system for potentially harmful nitrosamines.
- Full Text:
- Date Issued: 1974
- Authors: Thomson, Jennifer Ann
- Date: 1974
- Subjects: Bacteriophages -- Genetics Bacterial genetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4246 , http://hdl.handle.net/10962/d1007291
- Description: From Summary: A survey of collagenolytic aerobic bacteria from cured hides yielded three strains of Bacillus and eight of Achromobacter which degraded collagen at 0.4 M NaCl. Achromobacter sp. 2 was chosen for genetic studies due to its high collagenolytic activity and the lack of genetic information on Achromobacter. Four temperate bacteriophages specific for Achromobacter sp. 2 were isolated and their relationships studied. The phages caused lysogenic conversion resulting in the inability of lysogens to adsorb phage. Achromobacter sp. 2 was shown to be a cryptic lysogen as it was not immune to superinfection but had a very low rate of spontaneous induction which could be increased with mutagens. It is proposed that the cryptic lysogeny of this strain is maintained by a defective excision mechanism and the mode of prophage integration in the host chromosome. DNA extracted from phage α3a was used to transfect spheroplasts. The optimal conditions for the development of competence for transfection were determined. The presence of nuclease-attack on phage DNA under conditions of prolonged incubation of DNA and spheroplasts was proposed. A method for extracting Achromobacter DNA was devised which yielded purified, undegraded DNA, but it was not possible to transform Achromobacter sp. 2 with this DNA. The a phages were used to transduce a number of genetic markers into Achromobacter auxotrophs. The transduct ants had the ability to release the cryptic α3 prophage at a high rate while maintaining their sensitivity to homologous phage infection. It is proposed that this is due to complementation between the cryptic prophage and the residual phage functions in the transducing particles. The transductants segregated auxotrophs with a probability of 10⁻³ per cell per generation. It appears that an unusual system of generalised transduction is operating whereby the transducing particles contain both phage and bacterial DNA which is incorporated into the recipient genome by a single recombination event yielding unstable transductants. In a study on induction of Escherichia coli (λ), carcinogenic nitrosamines were shown to be inducers of phage development. This provides a screening system for potentially harmful nitrosamines.
- Full Text:
- Date Issued: 1974
Physico-chemical and substructural studies on Nudaurelia capensis β virus
- Authors: Struthers, J Keith
- Date: 1974
- Subjects: Imbrasia cytherea , Insects -- Viruses , RNA viruses , DNA
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4075 , http://hdl.handle.net/10962/d1007327 , Imbrasia cytherea , Insects -- Viruses , RNA viruses , DNA
- Description: From Introduction: The pine emperor moth, Nudaurelia cytherea capensis Stoll is an insect which, during the larval stage, causes extensive defoliation of the pine tree, Pinus radiata in the Cape province. These insects are susceptible to a virus disease, which on occasions causes large scale mortality. Five nonoccluded viruses have been shown to infect the pine emperor moth, and of these, one found in the greatest concentration, Nudaurelia capensis β virus (NβV) has been characterised to the greatest extent. This virus has been shown to contain RNA, to be isometric with a diameter of 36 mm, and to have a molecular weight of 16 million. The virus occurs in all stages of the insect's development, and by fluorescent antibody staining has been shown to develop in the cytoplasm of the host's cells. There have in recent years been a number of reports describing nonoccluded RNA viruses which appear to be similar to NβV. These are the viruses isolated from the moths Gonometa podocarpi and Antheraea eucalypti, and the one from the citrus red mite, Panonychus citri. These viruses have not been as extensively characterised as NβV, so the extent of the similarity between them and NβV is not known. However it would appear as if their discovery collectively heralds the emergence of a distinct new grouping within the nonoccluded RNA viruses of insects. This work reports the isolation and further characterisation of N. capensis β virus, its protein and nucleic acid.
- Full Text:
- Date Issued: 1974
- Authors: Struthers, J Keith
- Date: 1974
- Subjects: Imbrasia cytherea , Insects -- Viruses , RNA viruses , DNA
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4075 , http://hdl.handle.net/10962/d1007327 , Imbrasia cytherea , Insects -- Viruses , RNA viruses , DNA
- Description: From Introduction: The pine emperor moth, Nudaurelia cytherea capensis Stoll is an insect which, during the larval stage, causes extensive defoliation of the pine tree, Pinus radiata in the Cape province. These insects are susceptible to a virus disease, which on occasions causes large scale mortality. Five nonoccluded viruses have been shown to infect the pine emperor moth, and of these, one found in the greatest concentration, Nudaurelia capensis β virus (NβV) has been characterised to the greatest extent. This virus has been shown to contain RNA, to be isometric with a diameter of 36 mm, and to have a molecular weight of 16 million. The virus occurs in all stages of the insect's development, and by fluorescent antibody staining has been shown to develop in the cytoplasm of the host's cells. There have in recent years been a number of reports describing nonoccluded RNA viruses which appear to be similar to NβV. These are the viruses isolated from the moths Gonometa podocarpi and Antheraea eucalypti, and the one from the citrus red mite, Panonychus citri. These viruses have not been as extensively characterised as NβV, so the extent of the similarity between them and NβV is not known. However it would appear as if their discovery collectively heralds the emergence of a distinct new grouping within the nonoccluded RNA viruses of insects. This work reports the isolation and further characterisation of N. capensis β virus, its protein and nucleic acid.
- Full Text:
- Date Issued: 1974
Studies on anaerobic R factor transfer in facultative and anaerobic enteric bacteria
- Authors: Moodie, Hildegard Laura
- Date: 1974
- Subjects: Anaerobic bacteria , R factors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4252 , http://hdl.handle.net/10962/d1007684 , Anaerobic bacteria , R factors
- Description: Introduction: R factor mediated transfer of antibiotic resistance between Enterobacteriaceae has been reported to occur in the mammalian gastrointestinal tract (Farrar et al, 1972; Guinée, 1970; Kasuya, 1964; Reed et al, 1969; Wiedemann et al, 1970). In vivo conjugal transfer of genetic material has also been demonstrated with F¹, F⁺ and Hfr Escherichia coli strains (Jones & Curtiss, 1970). The environment in the lower gastrointestinal tract, where bacteria are abundant, is mainly anaerobic. This is demonstrated by the dominance of obligately anaerobic bacteria such as Bacteroides species (Finegold, 1969; Moore et al, 1969) and direct studies of intestinal gas composition (Askevold, 1956). However, most laboratory investigations of the incidence of R factors and their transfer frequencies have been performed under aerobic conditions using faecal facultative strains. The only investigation of resistance transfer under anaerobic conditions in vitro is that of Mitsuhashi (1965), who reported complete inhibition of transfer of an R factor from a Shigella flexneri donor to an Escherichia coli recipient. In addition, Fisher (1957) reported restriction of chromosomal transfer by an E. coli Hfr strain under anaerobic conditions in various media. On the basis of these results, it could be questioned whether in vivo R factor transfer is in fact possible (Chabbert et al, 1969). The contradictory situation prompted a reexamination of conjugation in facultative strains under anaerobic conditions. Both Fisher (1957) and Mitsuhashi (1965) obtained anaerobic conditions by evacuation. In this investigation, both mating and selection of recombinants were performed under stringent anaerobic conditions using methods developed for the isolation of obligate anaerobes (Hungate, 1969) to obtain a degree of anaerobiosis similar to that found in vivo.
- Full Text:
- Date Issued: 1974
- Authors: Moodie, Hildegard Laura
- Date: 1974
- Subjects: Anaerobic bacteria , R factors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4252 , http://hdl.handle.net/10962/d1007684 , Anaerobic bacteria , R factors
- Description: Introduction: R factor mediated transfer of antibiotic resistance between Enterobacteriaceae has been reported to occur in the mammalian gastrointestinal tract (Farrar et al, 1972; Guinée, 1970; Kasuya, 1964; Reed et al, 1969; Wiedemann et al, 1970). In vivo conjugal transfer of genetic material has also been demonstrated with F¹, F⁺ and Hfr Escherichia coli strains (Jones & Curtiss, 1970). The environment in the lower gastrointestinal tract, where bacteria are abundant, is mainly anaerobic. This is demonstrated by the dominance of obligately anaerobic bacteria such as Bacteroides species (Finegold, 1969; Moore et al, 1969) and direct studies of intestinal gas composition (Askevold, 1956). However, most laboratory investigations of the incidence of R factors and their transfer frequencies have been performed under aerobic conditions using faecal facultative strains. The only investigation of resistance transfer under anaerobic conditions in vitro is that of Mitsuhashi (1965), who reported complete inhibition of transfer of an R factor from a Shigella flexneri donor to an Escherichia coli recipient. In addition, Fisher (1957) reported restriction of chromosomal transfer by an E. coli Hfr strain under anaerobic conditions in various media. On the basis of these results, it could be questioned whether in vivo R factor transfer is in fact possible (Chabbert et al, 1969). The contradictory situation prompted a reexamination of conjugation in facultative strains under anaerobic conditions. Both Fisher (1957) and Mitsuhashi (1965) obtained anaerobic conditions by evacuation. In this investigation, both mating and selection of recombinants were performed under stringent anaerobic conditions using methods developed for the isolation of obligate anaerobes (Hungate, 1969) to obtain a degree of anaerobiosis similar to that found in vivo.
- Full Text:
- Date Issued: 1974
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