Characterisation of Human Hsj1a : an HSP40 molecular chaperone similar to Malarial Pfj4
- Authors: McNamara, Caryn
- Date: 2007
- Subjects: Heat shock proteins , Protein folding , Proteins -- Analysis , Proteins -- Structure , Plasmodium , Malaria , Molecular chaperones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4083 , http://hdl.handle.net/10962/d1007603
- Description: Protein folding, translocation, oligomeric rearrangement and degradation are vital functions to obtain correctly folded proteins in any cell. The constitutive or stress-induced members of each of the heat shock protein (Hsp) families, namely Hsp70 and Hsp40, make up the Hsp70/Hsp40 chaperone system. The Hsp40 J-domain is important for the Hsp70-Hsp40 interaction and hence function. The type-II Hsp40 proteins, Homo sapiens DnaJ 1a (Hsj1a) and Plasmodium falciparum DnaJ 4 (Pfj4), are structurally similar suggesting possible similar roles during malarial infection. This thesis has focussed on identifying whether Hsj1a and Pfj4 are functionally similar in their interaction with potential partner Hsp70 chaperones. Analysis in silico also showed Pfj4 to have a potential chaperone domain, a region resembling a ubiquitin-interacting motif (UIM) corresponding to UIM1 of HsjIa, and another highly conserved region was noted between residues 232-241. The highly conserved regions within the Hsp40 J-domains, and those amino acids therein, are suggested to be responsible for mediating this Hsp70-Hsp40 partner interaction. The thermosensitive dnaJ cbpA Escherichia coli OD259 mutant strain producing type-I Agrobacterium tumefaciens DnaJ (AgtDnaJ) was used as a model heterologous expression system in this study. AgtDnaJ was able to replace the lack of two E coli Hsp40s in vivo, DnaJ and CbpA, whereas AgtDnaJ(H33Q) was unable to. AgtDnaJ-based chimeras containing the swapped J-domains of similar type-II Hsp40 proteins, namely Hsj1Agt and Pfj4Agt, were also able to replace these in E. coli OD259. Conserved J-domain amino acids were identified and were substituted in these chimeras. Of these mutant proteins, Hsj IAgt(L8A), Hsj1Agt(R24A), Hsj1Agt(H31Q), Pfj4Agt(L 11A) and Pfj4Agt(H34Q) were not able to replace the E. coli Hsp40s, whilst Pfj4Agt(Y8A) and Pfj4Agt(R27A) were only able to partially replace them. This shows the leucine of helix I and the histidine of the loop region are key in the in vivo function of both proteins and that the arginine of helix II is key for Hsj1a. The histidine-tagged Hsj1a protein was also successfully purified from the heterologous system. The in vitro stimulated ATPase activity of human Hsp70 by Hsj1a was found to be approximately 14 nmol Pí[subscript]/min/mg, and yet not stimulated by Pfj4, suggesting a possible species-specific interaction is occurring.
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- Date Issued: 2007
Population size, demography and spatial ecology of cheetahs in the Timbavati Private Nature Reserve, South Africa
- Authors: Dyer, Siobhan Margaret
- Date: 2013
- Subjects: Timbavati Game Reserve (South Africa) Cheetah -- South Africa -- Timbavati Game Reserve Spatial behavior in animals Cheetah -- Behavior -- South Africa -- Timbavati Game Reserve Animal populations Population biology Rare mammals -- South Africa -- Timbavati Game Reserve Cheetah -- Effect of human beings on -- South Africa -- Timbavati Game Reserve
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5608 , http://hdl.handle.net/10962/d1002058
- Description: The cheetah (Acinonyx jubatus) has experienced a drastic decline in numbers over the last 20 years globally and is currently listed as vulnerable by the International Union for the Conservation of Nature (IUCN). In South Africa, there are only an estimated 763 free-ranging cheetahs and conflict with humans is arguably the most significant reason for this low number. The aim of my study was to determine the population size and demographic characteristics of the cheetah population within the Timbavati Private Nature Reserve (TPNR), South Africa, and to contribute to a better understanding of cheetah space use and habitat selection. The research was conducted on TPNR between November 2009 and June 2011 and I used a photographic survey to assess cheetah population size and demographic characteristics. Location data was obtained by collaring two adult male cheetahs with GPS/GSM collars and ad hoc sightings data from across the reserve for an adult female with cubs and three adolescent females. A relatively high minimum population density of 4.46 cheetahs/100km² was estimated, signifying a relatively healthy cheetah population. The sex ratio data indicated a higher male to female ratio and an average litter size of three cubs. The relatively high cub survival rate and density is promising in terms of the status of species within the area, as the data denote the success and potential persistence of the species. Cheetah home ranges varied between 20.97km² for the female with cubs and 659.65km² for the younger collared male. Season did not appear to be a determining factor in terms of home range sizes for the three social groups within the TPNR. However, the males did show a slight increase in their home range sizes during the dry season when resources where presumably more widespread. My results indicate that the cheetah is an adaptable species, flexible in behaviour and able to tolerate a variety of habitat types. Such knowledge is fundamental for planning and implementing the effective management and conservation of cheetahs in South Africa.
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- Date Issued: 2013
Group membership and collective action among small-scale farmers in Nkonkobe Local Municipality, Eastern Cape Province, South Africa
- Authors: Arwari, Margaret Kwamboka
- Date: 2017
- Subjects: Farmers -- South Africa -- Eastern Cape Farms, Small -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8144 , vital:31535
- Description: In South Africa, the organisation of farmers into groups has been a basic tenet for numerous, small and dispersed small-scale farmers to make their voices heard, address challenges and access support services from the government and other development agencies. However, the literature shows that the South African government promotes inappropriate forms of farmer collective action, i.e. collective production. The government seems to lack knowledge on what forms of collective action to implement and support. It is also noted in the literature that in South Africa, the majority of farmers do not participate in farmer organisations. There is limited research on the determinants of membership in farmer organisations, especially in terms of the role of ‘human agency’. Human agency is a concept which is interrelated with the concept of ‘empowerme nt’, whereby a person with strong agency is someone who is an agent of positive change. Therefore, the study sought to address these gaps. The broad objective of this study was to explore the phenomenon of group membership and collective action among small-scale farmers in Nkonkobe Local Municipality, Eastern Cape Province, South Africa. The study used the mixed method approach where an exploratory design was employed. A mult istage sampling technique was used which employed random, purposive and convenience sampling techniques. Quantitative and qualitative data were collected from 245 farmers using semistructured questionnaires and detailed qualitative data were elicited from 16 farmer organisat ions using interview guides. For the quantitative research, a cross-sectional survey design was employed. After discarded unusable observations, data from 228 farmers were analysed using a combination of descriptive statistics, simple inferential statistics, and econometric analysis. For the qualitative data obtained, thematic analysis was used in line with the study objectives. The study findings show that farmers undertake collective action through farmer organisations. These farmer organisations were categorised into two types, i.e. farmer cooperatives and farmer associations. However, low membership in these farmer organisations is noted and this was attributed to the following: (1) low farmer awareness of the existence of farmer organisations, (2) challenges faced by the organisations that contribute to their ineffectiveness and thus low membership, (3) the prevalence of negative perceptions of farmer organisations due to confusion as to their role, (4) the government’s farmer support approach which compels or encourages farmers to form groups. The results also showed that the following are determinants of participation in farmer organisations: farmer’s age, level of education, human agency, whether a farmer has off-farm income sources, whether a farmer is involved in government supported projects, whether a farmer accesses extension information, the number of visits from extension officers received by a farmer, and the number of adults in a household contributing family labour. The study findings also show that the farmers in farmer organisations have higher human agency compared to those not in farmer organisations. According to the study results, farmer groups offer a number of benefits. For one, farmer organisations are avenues for farmers’ voices to be heard, they lobby government for better access to support services such as credit, input supply, information, and training. In addition, farmers who belong to organisations experience the benefits of collective marketing. Despite the aforementioned benefits of farmer organisations, group challenges are observed. For example, farmer organisations face declining membership, the free rider problem and conflicts between members, have a problem of ineffective, old members and lack of commitment of some group members. It was therefore recommended that there is a need for concerted effort by the government, development agencies, non-governmental organisations, farmers, and farmer organisations to ensure the success of farmer organisations in promoting small-scale agriculture.
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- Date Issued: 2017
Mineralogical variation in the basal Upper Zone, Bushveld Igneous Complex, South Africa: implications for ore genesis and mineral extraction
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
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- Date Issued: 2017
Post-release evaluation and thermal physiology of the Pereskia stem-wilter, Catorhintha schaffneri (Coreidae), a new biological control agent for Pereskia aculeata (Cactaceae)
- Authors: Muskett, Phillippa Claire
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/36094 , vital:24477
- Description: Catorhintha schaffneri Brailovsky and Garcia (Hemiptera: Coreidae) is a biological control agent that was recently accepted for release in South Africa to control Pereskia aculeata Miller (Cactaceae), an invasive creeping cactus. The aim of this thesis was to conduct post-release research to ensure that C. schaffneri is utilised to its full potential. To achieve this aim, and focus release efforts, the thermal physiology of C. schaffneri was investigated to predict where in South Africa the agent is most likely to establish. These predictions were then tested by releasing the agent at field sites with a wide variety of climatic conditions and evaluating establishment success. When invasive plants invade a wide distribution, made up of areas with different climatic conditions, biological control agents may not establish or be effective throughout the invaded distribution. According to the thermal physiology of C. schaffneri, it is most likely to establish and become effective in the subtropical region of South Africa, along the coast of KwaZulu- Natal. Cold winters, or generally low year-round temperatures, may limit establishment in the more temperate areas of South Africa in the Eastern and Western Cape as well as inland in the Highveld region. These predictions can be used to focus release efforts to climatically suitable regions and stop releases in areas where C. schaffneri cannot survive. Predictions based on thermal physiology may not account for all of the variables which affect establishment. To account for other variables, the establishment of C. schaffneri was tested using closely monitored field release studies. During these studies the effect of other variables such as; microclimate temperature, humidity, precipitation, plant quality and release strategy were considered. Low humidity, precipitation and plant quality appear to affect the establishment of C. schaffneri in the subtropical areas of South Africa. The experiment was conducted during a period of drought, and this may have resulted in lower establishment rates. The most successful release strategy for C. schaffneri was the use of multiple, small releases rather than single releases of the same number of individuals. The field based study was therefore able to improve the biological control of P. aculeata by increasing the chance that each release of C. schaffneri results in establishment. The post-release studies presented in this thesis will increase the impact of C. schaffneri by focussing release efforts to climatically suitable sites, releasing at appropriate times of year and releasing the agent in a manner that increases establishment success. Post-release studies, such as those presented here, can make biological control programmes more efficient and effective.
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- Date Issued: 2017
Post-release evaluation of the biological control programme against Cereus jamacaru De Candolle (Cactaceae), in South Africa
- Authors: Sutton, Guy Frederick
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7982 , vital:21330
- Description: Cereus jamacaru De Candolle (Cactaceae) is an environment-transforming weed of both agricultural and wildlife habitats in South Africa. Weed infestations reduce carrying capacity of the land, and pose a risk to livestock, wildlife and human safety due to the plant’s spiny thorns. The weed is considered to be under complete biological control in South Africa, due to its introduced control agent, Hypogeococcus festerianus Lizer y Trelles (Hemiptera: Pseudococcidae), although observational reports suggest that the level of success achieved is variable. In this thesis, a formal post-release evaluation of this biological control programme was conducted, specifically to determine the efficacy of H. festerianus as a biological control agent, and to identify factors which may limit or constrain the level of success achieved by the control agent. These data were collected with the intention of improving the control of C. jamacaru in South Africa. A field-based study of C. jamacaru population demographics investigated the efficacy of H. festerianus as a biological control agent of the weed, by integrating weed growth, fecundity and survival metrics with C. jamacaru population dynamics and demographic patterns from 8 sites where H. festerianus was present and 14 sites where the control agent was absent. The findings indicated that H. festerianus significantly reduced weed fecundity, which resulted in fewer seedling recruits, and that levels of plant mortality were greater at sites where H. festerianus was present. The reduction in weed fecundity and survival translated into negative population-level consequences for H. festerianus. Weed-population age frequency distributions in the absence of H. festerianus demonstrated a “reverse J-shaped” distribution, indicative of high recruitment rates and population stability, while C. jamacaru populations infected with H. festerianus were described by bell-shaped distributions, and were typified by limited recruitment, or a complete lack thereof. By constraining recruitment and inhibiting selfregeneration, H. festerianus appears to regulate populations of C. jamacaru. Predation and parasitism of H. festerianus was believed to be a limiting factor for the biological control programme against C. jamacaru in South Africa, although no formal evaluation of this claim had been undertaken. Accordingly, the assemblage of natural enemies acquired by H. festerianus in South Africa was identified by field-collections of infected H. festerianus gall-material. Further, timed point-count surveys of natural enemies associated with H. festerianus were performed and integrated with the data on the impact of H. festerianus on weed population dynamics to assess the impact of two prominent predaceous taxa on H. festerianus efficacy as a biological control agent. Although H. festerianus had acquired a diverse suite of novel natural enemies in South Africa, this has not prevented the biocontrol agent from having an impact on C. jamacaru populations, although other subtler effects cannot be ruled out. This study showed that biological control efforts employing H. festerianus for the management of C. jamacaru have been successful. Furthermore, these data demonstrated the utility of retrospective analyses in developing and improving the science of biological control, specifically how to improve candidate agent prioritisation, determining how many agents are required for successful biological control, and how to evaluate the success of biological control efforts. Improvements in our theoretical understanding of biological control will undoubtedly reduce costs of biological control programmes, improve success rates, and increase the predictability of biological control.
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- Date Issued: 2017
Pollution potential of on-site dry sanitation systems associated with the Mzimvubu Water Project, Eastern Cape, South Africa
- Authors: Mamera, Matthew
- Date: 2018
- Subjects: Water resources development Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6038 , vital:29485
- Description: Protecting the environment requires tools that can be used to monitor environmental conditions for proper sustainable management of water resources. The Mzimvubu River is the largest undeveloped river, in the poorest region of South Africa. The South African government announced plans to construct two large storage dams (Ntabelanga and Laleni) in the Tsitsa River, one of the largest tributaries to the Mzimvubu River. The dams and associated infrastructure is termed the Mzimvubu Water Project (MWP). In developing countries like South Africa, several households use pit latrines. Moreover, many people also rely upon untreated groundwater supplies for their drinking water. The shared utilization of both pit latrines and groundwater resources, can lead to human and ecological health risks from microbial and chemical pollutants. These threats can be accelerated due to a permanent rise in the water table associated with dam constructions. Four hillslope sites with pit latrines (MT1, MT2, MT3 and MT4) above 1st order tributaries to the Tsitsa River, in the vicinity of the proposed MWP were chosen for this study. The soils were described and classified at selected locations below the pit latrine and above the tributary. Undisturbed core samples were from representative soil horizons on which hydraulic properties were determined in the laboratory. Samples were also collected to determine the feacal coliform and other bacterial concentrations during a winter and summer period. Mechanistic modelling with Hydrus 2D for a 121 day period was conducted to determine the risk of pollution to surface and groundwater from the various sites. Apedal soils of the Clovelly form dominated upper slopes of MT1 and the lower slopes of MT2. A Clovelly form is hydropedologically termed a recharge soil, as morphological indicators of saturation are absent. Hydromorphic soil properties were observed in the sub-surface B horizons of a Tukulu form in MT1-3 and MT4. High clay contents and strong structure soils of the Sepane form were dominant in MT3. The soils of MT1 and MT2 are relatively sandy with slightly higher hydraulic conductivities compared to MT3 and MT4. In general higher measured faecal coliform concentrations were higher in winter as compared to summer seasons but in most sites both winter and summer seasons had counts < 1 CFU/g. The highest concentrations of total bacteria (9 x 106 CFU/ g soil) was observed in MT3-1. Other sites with potential pollution include MT3-3, with a count above 4 x 104 CFU /g soil in winter and MT1-1 with a count above 2.2 X 104 CFU /g soil in summer. In most of the sites, the E. coli bacteria detections were low (< 1 CFU/g) during both seasons. The highest value in summer of 1.8 x 102 CFU/g was observed in MT3-3 which increased from 1.2 x102 CFU/g in winter. As the soil water flow rate increase the mobility of bacteria increase as well. Hydrus simulations showed that surface water resources are threatened by pollution from MT3 and MT4 due to the prominence of lateral flow. Groundwater pollution is more likely to occur on MT1 and MT2 as the soils are freely drained. Future work should focus on the more direct measurements and modelling of the migration of bacterial pollutants from pit latrines to various water resources.
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- Date Issued: 2018