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P15 trypanosome microtubule associated protein : structure/function analysis and vaccine development for the prevention of African sleeping sickness.Rasooly, Reuven. January 2001 (has links)
Trypanosomes are hemoflagellated protozoan parasites causing chagas disease in South
America, Leishmaniasis throughout the world, and African sleeping sickness in humans
and nagana in animals in Africa. About 55 million people and 25 million cattle have been
estimated to be at risk of contracting African sleeping sickness or nagana respectively.
Once injected into the blood stream via the bite of a tsetse fly, the parasite evades the
host's immune response by repeatedly changing its surface antigens, thus making the
development of a vaccine seem impossible. Furthermore, chemotherapy existing today can
be toxic, suggesting that novel methods to prevent diseases caused by trypanosomes are
essential.
All parasites of the Trypanosomatidae family contain unique microtubular structures called
the subpellicular microtubules. Microtubules are made of tubulin and of microtubule
associated proteins (MAPs). Unlike other microtubules, the subpellicular microtubules are
crosslinked to one another and to the plasma membrane. The unique structure of the
subpellicular microtubules has been attributed to unique trypanosome subpellicular MAPs
which stabilize the microtubule polymers and crosslink them to one another.
Three unique types of subpellicular MAPs have been identified: MARP, which is a high
molecular mass MAP that stabilizes microtubules, p52 that is a 52kDa MAP which
crosslinks microtubules, and pI5, which is a I5kDa protein which bundles microtubules.
Because trypanosome MAPs have been shown to be unique to these parasites, these
molecules could serve as useful target sites for therapy. In this study pI5 was cloned and
sequenced and shown to contain highly organized, nearly identical tandem repeats with a
periodicity of 10 amino acids, rich in positively charged and in hydrophobic amino acids.
It was shown that pI5 can also bind phospholipids, suggesting that it may not only
bundle the microtubule polymer through its positively charged amino acids but may also
crosslink the microtubules to the plasma membrane through its hydrophobic regions, thus
contributing to the stable structure of the subpellicular microtubules.
To test for the efficiency of pI5 as a vaccine candidate, the recombinant pI5 was cloned
into an adenovirus, which was used as a vaccine delivery system for pI5. Mice were
vaccinated with the native purified pI5, with the expressed recombinant pI5 and with the
adenovirus containing the recombinant pI5 gene (Ad-pI5). The results indicated that pI5
protected 100% of the animals vaccinated with the recombinant molecule (8/8), and 87%
of the animals vaccinated with the native protein (7/S), while none of the control animals
were protected. Animals that were vaccinated with the Ad-pI5 were protected but so were
the control animals vaccinated with an adenovirus containing the lacZ gene. We have
shown that vaccination with the adenovirus is associated with an elevated CDS+ T cell
response which is known to be trypanostatic (S6), suggesting that animals vaccinated with
Ad-pIS may have been protected not only by the specific anti-plS response but also by
non specific immunity that was induced by the adenovirus itself.
The source of the native and recombinant pI5 was from a different strain of T. brucei that
was used for challenge. Since the subpellicular microtubules are common to all members
of the Trypanosomatidae family, pI5 may ultimately serve as a common target for therapy
to all types of diseases caused by trypanosomes. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.
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Bioremediation of chemically contaminated soil : extraction/analysis methodology development.Khan, Fatima. January 2002 (has links)
The efficacies ofsoil extraction methods, namely, Soxhlet, sonication, agitation, alkaline digestion
and the ethyl acetate micro-method, for monitoring soil bioremediation were evaluated using three
soil types, Swartland, Rensburg and Hutton, encompassing the mineralogical range prevalent in Kwa
Zulu Natal. Phenol, atrazine and the BTEX component of petrol were the molecules used in this
study and were extracted under different spiking concentrations, after prolonged ageing times up
to 21 days and after changing the composition of the spiking solution. It was concluded that
extraction methods must be validated for the specific conditions under which they would be used,
taking into consideration, soil type, spiking solutions, moisture content, weathering times and the
analyte(s) in question. A preliminary appraisal of atrazine degradation in a Hutton soil was then
made under the conditions of sterilized, fertilized/non-fertilized and non-sterilized, fertilized/nonfertilized
soils. The predominant pathway of atrazine degradation was deemed to be
chemically/abiotically mediated due to the soil pH and the presence of iron and aluminium oxides
as well as the high levels of manganese in the soil. The results obtained prompted further study into
atrazinecatabolism using soil-slurry reactors, under the conditions of carbon-limitation, nitrogen
limitation, carbon/nitrogen non-limitation and carbon/nitrogen limitation. A comparison was made
between inoculated and non-inoculated bioreactors. The ability of the indigenous microbial
population to return the Hutton soil to its original pristine state was confirmed. The expense of
inoculation and culture maintenance could be avoided since carbon and nitrogen supplementation
would be as equally effective as inoculation. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.
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Genetic manipulation of saccharomyces cerevisiae for improved ethanol production from d-xylose.Govinden, Roshini. January 1999 (has links)
No abstract available. / Thesis (Ph.D.)-University of Durban-Westville, 1999.
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Development of a code of practice for co-disposal to obviate inimical environmental impacts of generated gases and leachates.Daneel, Richard A. January 1996 (has links)
Despite its phasing out in numerous countries, such as Germany and the U.S.A.,
co-disposal of hazardous waste with municipal solid waste continues to be widely practised
in South Africa. Co-disposal utilises properties and microbial activities in the refuse to
attenuate the hazardous waste and thus obviate its environmental impact potential. All
landfill operations require careful planning in not only site selection criteria but also the
type and amount of various wastes accepted for disposal. It is clear, however, that the
practice of co-disposal requires special precautions and management as the methods
employed in the landfill operation determine to a large extent the environmental effects
and, thus, the public acceptability of the operations.
Although co-disposal is not suitable for all industrial wastes the results of recent
research efforts, conducted mainly in the U.K., have indicated that, when properly
managed, co-disposal can be regarded as a safe and efficient disposal option for many
hazardous wastes. Environmental awareness in many European countries ensures that
numerous hazardous compounds are either recycled or recovered. Unfortunately, in South
Africa the lack of similar concern has resulted in increased concentrations of toxic
compounds being co-disposed on a regular basis. Since fundamental studies of this
technology, pertaining to South African conditions, have been lacking laboratory
models/microcosms were built to address this paucity.
Model. To effect the separation of species habitat domains of component species of
growth rate-dependent interacting microbial associations responsible for terminal catabolic
processes of the refuse fermentation, with retention of overlapping activity domains, and so
facilitate examination of species in isolation without violating the integrity of each
association, multi-stage models were constructed. The accidental overgassing of the culture
with liquid petroleum gas (LPG) effected interesting fermentation balance changes which
also emphasised the need for an Anaerobic Bioassay Test to assess the impacts of specific
perturbants. Evidence of differential susceptibility of the component species to phenol was
demonstrated in this study.
Microcosm. A total of 42 refuse packed single-stage glass column bioreactors were
commissioned and subjected to phenol and/or anaerobically digested sewage sludge codisposal.
The effects of four different operational modes: leachate discard (single elution);
leachate recycle; batch; and simulated rain on the co-disposals as well as refuse catabolism
per se were examined.
The results of these studies indicated that protracted periods of adaption to phenol (1000
and 2000 mg l -1) could have resulted from nutrient (elemental) limitation. Circumstantial
evidence was also gained which indicated that the nitrate- and sulphate-reducing bacteria
(SRB) were particularly sensitive to the added xenobiotic. Further, without the effective
participation of the nitrate- and SRB the active and total fermentation of both the phenol
and refuse components were depressed. It was also determined that the operating regime
employed was a key factor in refuse degradation although with time, and especially
following the phenol resupplementations, the operating conditions played a less significant
role. In general, the single elution operated columns demonstrated increased phenol
removal rates which were, unfortunately, coincident with low pH values and increased
leachate residual phenol concentrations. Leachate recycle, on the other hand, unlike the
batch operated columns, facilitated increased pH values and methane evolutions. The
simulated rain columns were characterised by rapid washout of the added phenol as well as
methanogenic precursors.
The sewage sludge co-disposal experiments, likewise, demonstrated that, depending on
the sludge:refuse ratio, the operating regime was extremely important in optimising the
refuse degradation processes although, in general, leachate recycle appeared to be the most
favoured method of operation. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1996.
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Microbiological investigations into granular sludge from two anaerobic digesters differing in design and industrial effluent purified.Howgrave-Graham, Alan R. January 1995 (has links)
Due to a combination of selection criteria, sludges from upflow anaerobic digesters
treating industrial waste waters consist primarily of well-settling, dense agglomerates
called granules. Quantification of the component mixed microbial populations of these
granules has been severely restricted by the inability of researchers to disrupt them
without concomitantly destroying numerous cells. In situ quantification using light and
electron microscopy is complicated by the high cell numbers and bacterial diversity; the
small cell size; and the destructive nature of electron microscopy preparative
techniques preventing the viewing of more than a small percentage of the population
at a time. For these reasons, in this investigation, standardization of qualitative electron
microscopic techniques was performed prior to their application to granules. Isolation
and electron and light microscopic techniques were applied to granules from a fullscale
clarigester treating effluent from a maize-processing factory. In addition, a
method using montaged transmission electron micrographs (TEMs) taken along a
granule radius, and image analysis, was developed for bacterial quantification within
granules. This method, together with antibody probe quantification, was applied to
granules from an upflow anaerobic sludge blanket (UASB) digester treating a brewery
effluent. The clarigester granules contained a metabolically and morphologically diverse
population of which many members were not isolated or identified. By contrast, the
UASB digester granules consisted primarily of morphotypes resembling Methanothrix,
Methanobacterium and Desulfobulbus, in order of predominance. However, only about
one-third of the population reacted with antibody probes specific to strains of bacterial
species expected to occur within these granules. According to the antibody probe
library used, the Methanobacterium-like cells observed in TEMs were probably
Methanobrevibacter arboriphilus. From this study it is apparent that different anaerobic
digester designs, operational parameters, and the chemical composition of the waste
water purified, are factors which influence the formation and maintenance of granules
differing with respect to their microbial populations. Until the difficulties associated with
quantification are overcome, the processes governing granule formation and/or
population selection will remain obscure. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1995.
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The microbiology of ex situ bioremediation of petroleum hydrocarbon-contaminated soil.Snyman, Heidi Gertruida. 18 June 2013 (has links)
Bioremediation is the process whereby the degradation of organic polluting compounds
occurs as a result of biochemical activity of macro- and microorganisms. Bioremediation of
hydrocarbon contaminated soils can be practised in situ or ex situ by either stimulating the
indigenous microorganisms (biostimulation) or introducing adapted microorganisms which
specifically degrade a contaminant (bioaugmentation).
This investigation focused on ex situ remediation processes with special attention to the
processes and microbiology of landfarming and thermal bioventing. Landfarming was
investigated at pilot-scale and full-scale, and thermal bioventing at laboratory and pilot-scale.
This study indicated that pilot-scale bioremediation by landfarming was capable of effecting
a total petroleum hydrocarbon concentration (TPHC) reduction of 94% (m1m) from an
initial concentration of 320 gkg-I soil to 18 gkg-I soil over a period of 10 weeks. Reactors
receiving biosupplements showed greater rates of bioremediation than those receiving
nutrients. Promotion of TPHC catabolism by addition of a commercial or a site-specific
microbial biosupplement was similar. Seedling experiments proved that bioremediation did
not necessarily leave the soil in an optimal condition for plant growth.
The full-scale landfarming operation reduced the TPHC concentrations from 5 260 -
23 000 mgkg- I to 820 - 2335 mgkg- I soil over a period of 169 days. At full-scale, the larger fraction of more recalcitrant and weathered petroleums. and the less intensive treatment
resulted in a slower rate of TPHC reduction than was found in the pilot-scale study. Three
distinct decreases in the TPHC were observed during the full-scale treatment. These
presented an ideal opportunity to investigate the microbiology of the soil undergoing
treatment. The dominant culturable microorganisms were isolated and identified. The
bioremediation process was dominated by Bacillus and Pseudomonas species. The method
used to study the population was, however, biased to culturable, fast growing
microorganisms which represent a small portion of the total microbial population. For this
reason, a method to study the total eubacterial population in situ with rRNA targeted
oligonucleotide probes was adapted and found to be a valuable technique.
Soil microorganisms respiratory activity was investigated at different times in the full-scale
treatment. A clear correlation between activity and degradation was recorded. The effect of
a supplement. anaerobically digested sludge, was also assessed by this method.
Thermal bioventing was investigated as an ex situ in-vessel treatment technology for small
volumes of highly contaminated soils. This proved to be a viable technique for the
bioremediation of petroleum hydrocarbons at laboratory-scale. Volatilisation contributed to
at least 40% of the reduction. Of the two supplements evaluated. dried sludge promoted
degradation to a greater extent than chicken manure.
The pilot-scale study proved that a chemical contaminant reduction of at least 50% could be
achieved in 13 weeks by thermal bioventing. Of the supplemented reactors. the presence of dried sludge and commercial biosupplement etfected the largest contaminant decrease. As a
possible supplement to increase the rate of bioremediation. dried anaerobically digested
sludge was more effective than chicken manure. A parallel laboratory-scale experiment
gave similar results. Gravimetric analyses were found to be conservative indications of the
remediation process.
The results of this study shed some light on our. still. limited understanding of
bioremediation. The gap between the technology in the laboratory and field was narrowed
and a better understanding of the soil microbiology was achieved. Due to the limited
control of environmental parameters in the case of landfarming. thermal bioventing was
investigated and proved to be an effective alternative. The latter technology is novel in
Southern Africa. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1996.
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Development of a bioreactor system using a pine bark matrix for the removal of metal ions from synthetic aqueous solutions.Van Zuydam, Jason Peter. 06 November 2013 (has links)
Many industries use, or produce, metal-containing solutions which must be
treated for reuse or discharge to sewer. One such treatment is biological and both living and dead materials have been investigated for the abstraction of metal ions from solution. Studies on systems containing only a single biosorbent are well documented, and mostly involve optimisation of biosorption capacities and metal uptake rates through modification of Biological Support Particle (BSP) size and surface characteristics. Literature on dual biosorbent studies is sparse. The commercial application of biosorption technology in wastewater treatment remains largely unexplored and unexploited. The primary objective here was to assess the potential of forced-upflow packed-bed bioreactors, containing dual biological sorbents, for treating a synthetic wastewater containing copper, zinc and cadmium, at both laboratory- and pilotscale.
Pine bark was selected as BSP since it is an abundant, relatively cheap,
agricultural waste product in South Africa, and is known to sorb metal ions. Initial experiments aimed to optimise biofilm development on the pine bark surfaces, since microbial biomass is also known to sequester metal ions. Systems comprising either one, or both, these biosorbents were compared for their efficiency in metal removal. The effects of type, size, and state of decomposition, of the pine bark, the addition of supplementary nutrients (Voermolas) and the mixing conditions, on the metal biosorption capacity and reaction kinetics of the systems were also studied. All experiments were conducted at an initial metal concentration of 100mg.ℓ⁻¹with both composted and uncomposted pine bark as BSP. The former supported
microbial colonisation and resisted biofilm sloughing, but degraded rapidly
causing engineering difficulties. Uncomposted pine bark showed the same ability, but was also physically more robust.
Organic compounds leached from the pine bark did not hinder microbial
colonisation of the BSP; rather they served as additional nutrients. Literature studies suggest that these compounds would not significantly compromise the COD or increase the toxicity of the final effluent. Biofilms developed without supplementary nutrients, but Cd²⁺ and Zn²⁺ were sorbed more effectively in bioreactors containing Voermolas (39% and 38% Cd²⁺ removal, 36% and 32% Zn²⁺ removal, in 0.2% and 0.1% Voermolas solutions respectively) than in unsupplemented systems (25% Cd²⁺ removal and 20% Zn²⁺ removal). Conversely, Cu²⁺ was removed most efficiently in the absence of supplementary nutrients. Based on biosorption of the target metal ions, 0.1% (v/v) Voermolas was the most effective concentration of supplementary nutrients.
Raw, un-colonised pine bark nuggets (16-24mm), and plastic bioballs
(commercially available, bespoke BSP), were compared in laboratory-scale
bioreactors by measuring the decrease in residual metal ion concentrations over time, and changes in the solution pH. These experiments showed that the two BSPs did not differ significantly in their performance as a support matrix, or as a metal sorbent (30.6% and 32.6% of metal ion remained in solution when using bioballs and pine bark respectively). However, the presence of a biofilm on both these BSPs, improved the overall performance of the bioreactors significantly (for the bioball BSP, residual metal ion levels decreased from 30.6%, in the absence of a biofilm, to 11.0% with a biofilm present. Similarly, for the pine bark BSP, residual metal ion levels decreased from 32.6%, in the absence of a biofilm, to
7.3% with a biofilm present). A cost comparison of the two BSPs showed that raw pine bark nuggets were available at less than 0.1% of the cost of the bioballs. At pilot-scale, modelled kinetic data compared poorly with experimentally determined results, but minimum residual metal concentrations for Cu (1.7mg.ℓ⁻¹) and Zn (4.2 mg.ℓ⁻¹) were below South African (eThekwini Municipality) regulatory limits for discharge to sewer (5mg,ℓ⁻¹ for both), and sea outfall (3mg.ℓ⁻¹ Cu and 20mg.ℓ⁻¹ Zn). However, for Cd the final residual metal concentration (5.6mg.ℓ⁻¹) was above the regulatory discharge threshold for any receiving system.
Although some of the effluents from the system investigated could not be legally released into the municipal sewer system without further remediation, the study showed that a system combining living and dead biomass in a single reactor is capable of significantly reducing dissolved metal concentrations in synthetic wastewaters without temperature or pH adjustment. Furthermore, such a system can operate at pilot-scale, where a pine bark matrix represents a significant cost saving over conventional plastic BSPs. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
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Glucocorticoid receptor promoter expression and apoptosis induction in small cell lung cancer.Singh, Nimisha. 25 November 2013 (has links)
Lung cancer is the most common cancer worldwide and is the fourth leading cause of death in South Africa. Lung cancer is categorised into two types; non-small cell lung cancer and small cell lung cancer (SCLC). SCLC constitutes 20% of all lung cancers and is considered to be an aggressive tumour as it gains chemo-resistance and exhibits early metastasis in diagnosed patients. SCLC cells originate from the neuroendocrine cells of the bronchoepithelium and are known to secrete the neuropeptide, proopiomelanocortin (POMC). POMC undergoes proteolytic cleavage to produce the adrenocorticotropin hormone (ACTH). ACTH stimulates the production of the steroid hormone, glucocorticoid hormone (GC), through the hypothalamus-pituitary-adrenal (HPA) axis. The produced GCs mediate a negative feedback system of the HPA axis to sequester ACTH production. SCLC cells are insensitive to this negative feedback stimulus. GCs elicit their actions through the glucocorticoid receptor (GR). Studies have shown that SCLC cells have a reduced expression of GR which perpetuates the GC-insensitivity. Importantly, over-expression of exogenous GR in SCLC cells leads to cell death by apoptosis. It was postulated that SCLC cells select against GR expression for longevity. Cancer cells are known to alter/silence the expression of tumour suppressor genes by a mechanism known as methylation. Methylation occurs when the enzyme, DNA methyltransferase 1, adds a methyl group to a cytosine present in a guanine-cytosine rich region of the gene (CpG island). The GR gene has a 5’-untranslated exon 1 region that consists of eight promoter regions (1A-1J), in these promoter regions are many CpG islands that have the potential to be methylated.
The first aim of this study was to determine the promoter/s utilised by SCLC cells to express the GR protein. Conventional PCR revealed that all three cell lines predominantly utilise promoters 1B and 1C for GR expression. Bioinformatic analysis revealed that these promoters contain putative CpG islands and new data suggests that the GR is silenced by methylation and that treatment with a de-methylating agent results in GR re-expression. To determine which promoter is responsible for GR re-expression after de-methylation, the SCLC cell line, DMS79, as well as two control cell lines, A549 and HEK cells, were treated with the de-methylating agent, 5-aza-2’-deoxycytidine, for 72 hours. qPCR analyses revealed that all three cell lines expressed promoters 1B and 1C with A549 cells showing no evidence of methylation. The HEK cells showed methylation in promoter 1C and not promoter 1B. The SCLC cells showed
methylation in both promoter 1B and 1C, however, only promoter 1B showed a significantincrease in transcript levels. SCLC cells are induced to undergo GC-mediated apoptosis when GR expression is restored however the mechanism utilised by the GR to induce the apoptotic cascade is unknown. The GR structure is divided into three domains; ligand binding domain (LBD), DNA binding domain (DBD) and amino terminal domain (NTD). The second aim of this study was to determine the component of the GR that induces apoptosis of SCLC cells. HEK and SCLC cells were infected with empty virus and various GR construct viruses; containing either a wild-type GR, ligand binding mutant, DNA binding mutant or a transactivation mutant (NTD); for 72 hours. Both cell lines were quantified for apoptosis and cell death using microscopic analyses. In HEK cells, it was shown that apoptosis occurred in cells expressing the wild-type GR, the DNA binding mutant and transactivation mutant constructs but apoptosis was reduced in cells expressing the ligand binding viruses. This indicates that the LBD may be necessary for inducing apoptosis in HEK cells. In DMS79 cells, apoptosis occurred in cells expressing the wild-type GR, ligand binding mutant and the DNA binding mutant constructs. There was less apoptotic activity exhibited in the transactivation constructs which indicates the NTD may be necessary for apoptosis induction in these cells.
The NTD of the GR is responsible for interaction with other transcription factors to mediate GR transcriptional activity and this study has shown that the transactivation domain plays a necessary role in apoptosis induction. An analysis of the various pathways the GR interacts with through the NTD domain could lead to the identification of the pathway which triggers apoptosis in SCLC cells. This discovery, together with knowledge of promoter methylation and expression may contribute to the development of new, more effective therapies for SCLC. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.
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Optimizing biocontrol of purple nutsedge (Cyperus rotundus).Brooks, Edward J. January 2006 (has links)
Cyperus rotundus L. CYPRO (purple nutsedge) and Cyperus esculentus L. CYPES (yellow
nutsedge) are problematic weeds on every continent. At present there is no comprehensive
means of controling these weeds.. The primary means of control is herbicides, although the
weeds are becoming more resistant. Bioherbicide control of purple and yellow nutsedge is an
important avenue of research, with much of the focus being to increase the virulence of current
fungal pathogens of C. rotundus and C. esculentus.
The primary aim of this study was to increase the virulence of a fungal pathogen of C. rotundus
and C. esculentus, with the objective of creating a viable bioherbicide.
A possible means of increasing the virulence of a pathogen would be to increase the amount of
amino acid produced by the fungus. This was proposed as a means of increasing the virulence of
Dactylaria higginsii (Luttrell) M. B. Ellis. Overproduction of amino acids such as valine and
leucine result in the feedback-inhibition of acetolactate synthase (ALS), an enzyme which is a
target for many herbicides currently on the market. By applying various amino acids to tubers of
purple nutsedge and comparing the results with a reputable herbicide, glyphosate, it was possible
to determine the success of the amino acid applications. Only glutamine treatment at 600 mg.r1
resulted in significantly less (P<O.OOI) germination compared with the water control, while the
glyphosate application resulted in no germination. Four treatments were significantly different
(P<O.OOI) from the water control in terms of shoot length, but no pattern or conclusion could be
drawn from the results. Injecting amino acids and glyphosate into the leaves of the plants gave
similar results to those obtained with the tubers, with no visible damage on those plants injected
with the amino acids and complete plant death of those injected with glyphosate. Amino acids
had little effect on the growth of the C. rotundus plant or tuber. It was later determined by a
colleague (Mchunu1
, unpublished) working on the same project, that D. higginsii does not infect
the local ecotypes of C. rotundus in Pietermaritzburg, South Africa.
A second fungus, Cercospora caricis Oud., was isolated from C. rotundus growing in the region,
and confirmed as a Cercospora species by conidial identification. Like many Cercospora
species, C. caricis produces a phytotoxin, cercosporin. An increase in production of cercosporin
would theoretically lead to an increase in virulence of C. caricis. Mutation of hyphae by
i
J Makhosi Mchunu: Address: National department ofAgriculture; Private Bag 3917; Port Elizabeth; 6056
Email: Makhosimc@NDA.agric.za
ultraviolet-C light was perfected on C. penzigii Sacc., where 5 min exposure to DV-C light
resulted in approximately 99% cell death. Surviving colonies were analysed by spectrophoresis,
and the surviving mutant gave an absorbance value of approximately 5% more than the median.
Samples were analysed by high-performance liquid chromatography (HPLC) to determine the
presence of cercosporin. No definitive result was obtained. Exposure of C. caricis to DV-C for
5 min. resulted in approximately 65% hyphal cell death, with 20 min. resulting in approximately
95% death. A spontaneous mutant was observed in a colony that had been exposed to DV-C.
This mutant showed sectored growth with red and grey growth patterns. The red section of the
mutant was subcultured and analysed by spectrophoresis and HPLC. The red C. caricis gave an
absorbance reading of approximately 140 on HPLC compared with about 22 from the grey
colony. HPLC analysis of the wild-type C. caricis did not produce a peak corresponding to that
of the cercosporin standard, although no conclusion could be obtained on the presence or
absence ofthe toxin.
The virulence of the mutant C. caricis could not be determined as inoculation experiments were
unsuccessful, and had to be discontinued due to time constraints. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
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The effect of water treatment residues on soil microbial and related chemical properties.Pecku, Shantel. January 2003 (has links)
Water treatment residue (WTR), a by-product of the water treatment process,
consists primarily of precipitated hydroxides of the coagulants used in the water
treatment process, along with sand, silt, clay, humic compounds, and dissolved
organic matter. It is usually disposed of by landfill, a technology with numerous
problems that include dwindling landfill capacity, extensive dewatering
requirements for the WTRs, high costs of transportation, and potential liability for
landfill clean-up. Therefore, land disposal (or land treatment) presents a popular
alternative disposal method based on the principle that the physical, chemical,
and microbial properties of the soil can be used to assimilate applied waste
without inducing any negative effects on soil quality.
The objective of this study was to investigate the effects of land disposal of the
WTR generated by Umgeni Water, a local water treatment authority, on soil
quality. These effects were investigated using depth samples from soil profiles of
Westleigh and Hutton soil forms at field trials located at Ukulinga Research Farm,
near Pietermartizburg and Brookdale Farm, Howick, KwaZulu-Natal, South
Africa, respectively. Four rates of WTR (0, 80, 320, and 1280Mg ha-1
incorporated into the soil) were investigated at both trials, in addition to mulched
treatments at rates of 320 and 1280Mg ha-1 at Brookdale only. Sampling of plots
was carried out in September 2001 and May 2002, and all treatments were
investigated under fallow and grassed cultivation. Laboratory measurements
used to assess soil quality included pH, electrical conductivity (EC), organic
carbon (QC), and microbial activity using f1uorescein diacetate (FDA) hydrolysis.
At both trials in September 2001 WTR-amended plots displayed higher pH in the
0-200mm soil in comparison to the controls, whereas by May 2002 pH had
returned to the condition of the controls. Addition of WTR at Ukulinga resulted in
higher QC in September 2001, but in May 2002 this was similar to the controls.
However, at Brookdale QC was unaffected by WTR. At Ukulinga and Brookdale the effect of WTR on EC was variable, and microbial activity in the soil profile
was unaffected by WTR addition.
Observations at Ukulinga and Brookdale reflected long term changes (3 and 5
years, respectively) to soil quality following WTR addition. To examine the initial
changes in soil quality a laboratory experiment was set up using the field trial
soils. Research objectives were also extended to include WTRs from Rand
Water (Johannesburg), Midvaal Water Company (Stilfontein), Amatola Water
(East London), and two samples from the Faure Water Treatment Plant (near
Cape Town). The second Faure sample (Faure2
) was collected when blue green
algal problems were experienced at the plant. The measurements used to
investigate these short term effects on soil quality were soil pH, EC, and
microbial activity as indicated by respiration rate.
Each of the WTRs added to the Hutton and Westleigh soils increased soil pH by
varying increments, and the higher the WTR application rate, the higher was the
pH recorded. With the exception of the Rand and Umgeni WTRs that clearly
increased soil EC, the effect of the otherWTRs on EC was variable. The Faure1
and Amatola WTRs appeared to have no effect on microbial activity, whereas the
Umgeni, Rand, Midvaal, and Faure2 WTRs stimulated microbial activity by Day 2
following the addition of WTR, but this had declined by Day 14. As for pH, higher
microbial activity was recorded at higher WTR application rates.
Changes in microbial community structure of the Hutton soil only, following the
addition of WTR were examined using denaturing gradient gel electrophoresis
(DGGE) analysis. Community profiles of the different WTRs proved to be
markedly different. However, WTR-amended soil retained banding patterns
consistent with the control soil indicating that dominant populations in the Hutton
soil had been retained. The field trials indicated that long term effects of land disposal of WTR were not
detrimental to the measured indicators of soil quality namely, pH, EC, QC, and
microbial activity. The laboratory assessments of the short term response of the
Hutton and Westleigh soil forms to WTR addition suggested that the tested
variables were altered by WTR, but not significantly changed to the detriment of
soil quality. Microbial community analysis indicated that the community structure
of the Hutton soil was not significantly altered by WTR amendments. Present
findings provide no evidence to suggest that land disposal of WTR is detrimental
to soil quality. It is therefore regarded as a feasible disposal option although
there are some aspects that should be investigated further. These include
investigations into rhizosphere/microbial interactions and the feasibility of
growing cash crops. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.
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