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No / The most important issue during synthesis of nanoparticles (NPs) is to avoid particle agglomeration and adhesion. There have been several attempts to use special substances such as organic surfactants, polymers and stable ligands for this purpose. In this study, silver NPs were synthesised with and without gelatin macromolecules, as a green natural biopolymer, which resulted in NPs with varying shapes and sizes. The effect of morphological characteristics on the antibacterial and antifungal properties of the synthesised NPs were studied, by comparing Gram-negative (Escherichia coli) versus Gram-positive (Staphylococcus aureus) bacteria as well as fungi (Candida albicans) by calculation of minimal inhibition concentration value. The results corresponded well with the assumptions on the effects of shape and size on the antibacterial and antifungal properties of the studied NPs.

M.S.

The feasibility of ensiling broiler litter alone, with added water or with high moisture corn grain was evaluated. Wood shaving based broiler litter was ensiled in small laboratory silos (about 4 liters) at moisture levels of 15.6 (no water added), 20, 30, 40 and 50%. Maximum fermentation was approached at 40% moisture as measured by silage pH and levels of lactic and acetic acids and water-soluble carbohydrates. Coliform bacteria were eliminated by ensiling at 20 to 50% moisture. In a subsequent study, litter was ground and 545 kg were ensiled alone (22% moisture) or with added water to elevate the moisture to 40%. Active fermentation occurred, and coliforms were eliminated in the silage containing 40% moisture. Twenty-four wethers and 12 steers were used in a metabolism study and a palatability study, respectively. Four rations were supplemented with: (1) dry heat processed litter [260 C at a depth of 1.3 cm for 30 min.]; (2) 22% moisture litter silage; (3) 40% moisture litter silage; or (4) soybean meal. Supplements supplied 50% of the dietary nitrogen in the metabolism trial. Nitrogen retention was lower (P<.01) for the ration supplemented with processed litter than for the other rations. Apparent digestibility was not significantly different among the three rations supplemented with litter, but digestion coefficients for dry matter and crude fiber were lower (P<.05) for the ration supplemented with soybean meal. Litter supplied 50% of the total ration dry matter in the palatability study. Dry matter intakes by cattle were similar for the two rations containing litter silage and were significantly (P<.01) lower than for cattle fed the conventional soybean meal supplemented ration. In another study, ground high moisture (26%) corn grain was ensiled alone or with ground litter in a 2 to 1 ratio in approximate 1 metric ton masses. The extent of fermentation in the corn-litter mixture was less than in corn ensiled alone. Twenty-four wethers were used in a metabolism trial and 12 steers were individually fed in two 15-day palatability trials. The four rations tested in both studies contained: (1) ensiled corn; (2) ensiled corn-litter mixture; (3) ensiled corn and dry heat processed litter [260 C at a depth of 1.3 cm for 30 min.]; or (4) ensiled corn and soybean meal. Nitrogen intake was similar for the three supplemented rations (2, 3, 4) fed in the metabolism study. Nitrogen retention was lowest (P<.01) for the unsupplemented ration (1). Retention was significantly higher (P<.01) for the soybean meal than for the litter-containing rations. This can be attributed mainly to lower fecal nitrogen excretion. Coefficients of apparent digestibility were usually significantly lower for the unsupplemented than for the supplemented rations. Apparent digestibility of crude protein was lower (P<.01) for both litter-containing rations than for the soybean meal supplemented ration. Digestion coefficients for dry matter, crude fiber, and NFE were not significantly different among rations 2, 3 and 4. Dry matter intakes tended to be higher for cattle fed litter than for those fed the soybean meal supplemented ration. Intake was lowest (P<.01) for the unsupplemented ration. / Ph. D.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: In this dissertation, I grapple with the problem of global drug resistance and moral responsibility which, as far as I am aware, has so far not been presented as a topic of ethical inquiry. It represents a conundrum involving three major factors: microbial adaptation and change, human social factors and environmental changes. Drug resistance is a phenomenon in which certain microorganisms, when exposed to antimicrobial agents, may acquire the beneficial trait of drug resistance which ensures a better potential for their survival. The acquired trait of drug resistance I argue renders such microorganisms 'supra-natural '. Supra-natural is a term I coin for entities that have been imposed upon nature by human design; they do not follow the natural evolutionary processes of adaptation and change. Drug resistance is classified as an emerging infectious disease. Human social factors and environmental change (particularly population growth, density and consumerist practices) enhance the rise of emerging infectious diseases. Through such increasing destructive practices, stress is placed on the environment. Environmental stress facilitates the rise of new and old infectious diseases and the spread of drug resistant supra-natural microorganisms. Thus, our ability to treat successfully illnesses and injuries in humans, animals and plants is increasingly impaired. Morally, we are responsible for the problem of global drug resistance. Drug resistant microorganisms exist in nature and concerning this, we can do nothing. At best, we can only try to control the problem using prudential measures. The problem of global drug resistance represents both a biomedical ethical and an environmental ethical issue. Is there a way out of the human-nature debate? Through Bryan Norton's enlightened anthropocentrism, I identify the ways in which his thesis may be applied to the problem of human and environmental concerns and show its applicability in broadening the parameters of biomedical ethics education to include environmental concerns. Key words: biomedical ethics, environmental ethics, drug resistance, Supra-natural' microorganisms, ethics education, enlightened-anthropocentrism. / AFRIKAANSE OPSOMMING: In hierdie proefskrif bespreek ek die probleem van die verskynsel dat mikroorganismes op 'n globale skaal weerstand begin bied teen mediese middels (globale middel-weerstandigheid) en die morele verantwoordelikheid wat dit oproep - 'n probleem wat, na my beste wete, nog nooit aangebied is as 'n tema van etiesfilosofiese ondersoek nie. Dit verteenwoordig 'n kompleks van drie belangrike oorwegings: mikrobiese aanpassings en veranderinge, menslike sosiale faktore, en omgewingsveranderinge. Middel-weerstandigheid is 'n verskynsel waarin sekere mikro-organismes, wanneer hulle blootgestel word aan antimikrobiese agente, die (vir hulself) voordelige kenmerk kan bekom van weerstandigheid teen die middel; iets wat 'n beter potensiaal vir hul eie oorlewing verseker. Hierdie bekomde kenmerk (middel-weerstandigheid) maak, volgens my argument, sulke mikro-organismes 'supra-natuurlik'. Supra-natuurlik is 'n term wat ek munt vir entiteite wat aan die natuur blootgestel is as gevolg van menslike ontwerp; hulle volg nie die natuurlike evolusionêre prosesse van adaptasie en verandering nie. Middel-weerstandigheid word geklassifiseer as 'n opkomende aansteeklike siekte. Menslike sosiale faktore en omgewingsveranderinge (veral bevolkingsgroei, -digtheid and verbruikerspraktyke ) vergroot die opkoms van aansteeklike siektes. Deur sodanige toenemende destruktiewe praktyke word stres geplaas op die omgewing. Omgewingstres fasiliteer die opkoms van nuwe en ou aansteeklike siektes asook die verspreiding van weerstandige supra-natuurlike mikro-organismes. Ons vermoë om siektes en beserings van mense suksesvol te behandel, word gevolglik toenemend ondermyn. Moreel gesproke is ons verantwoordelik vir die probleem van globale middelweerstandigheid. Middel-weerstandige mikro-organismes bestaan in die natuur, en aan daardie feit as sodanig kan ons niks doen nie. Ons kan, ten beste, probeer om die probleem te beheer deur middel van verstandige maatreëls. Die probleem van globale middel-weerstandigheid verteenwoordig sowel 'n biomedies-etiese as 'n omgewingsetiese kwessie. Is daar 'n uitweg uit die mens-natuur debat? Ek identifiseer, met 'n beroep op Bryan Norton se swak antroposentrisme, maniere waarop sy tese toegepas sou kon word op die probleem van menslike en omgewingsoorgwegings Ek wys ook op die toepaslikheid daarvan vir die verbreding van die parameters van biomediese etiek-opvoeding ten einde omgewingsoorwegings deel van lg. te maak. Kembegrippe: biomediese etiek, omgewingsetiek, middel-weerstandigheid, 'Supra- . natuurlike' mikro-organismes, etiek-opvoeding, swak antroposentrisme.

Antibiotic resistance profiles of fecal coliform isolated from unchlorinated and chlorinated secondary effluent were determined. Of 332 fecal coliforms isolated from chlorinated effluent a mean of 48% were multiply antibiotic resistant. In contrast, of 347 fecal coliforms isolated from unchlorinated effluent a mean of 29% were multiply antibiotic resistant. Resistance to ampicillin, cephalothin, and carbenicillin were significantly higher in the former than the latter. Randomly selected isolates survived and/or grew in sterile and unsterile effluent retaining resistance patterns for 40 days. Resistance factors were transferred in laboratory medium at frequencies from 0 to 1.2 x 10⁻² (number of recombinants/number of recipients) and in sterile neutralized tertiary effluent at frequencies from 0 to 1.0 x 10⁻⁴. Resuscitative techniques were necessary for optimal recovery of fecal coliforms from effluent using selective media. Antibiotic resistance patterns of fecal coliforms isolated from unchlorinated and chlorinated effluent was not associated with chlorine or heavy metal resistance. Multiply antibiotic resistant fecal coliforms from chlorinated effluent were significantly less sensitive to lytic phage than multiply antibiotic sensitive fecal coliforms from unchlorinated effluent (p < .05). Using group discriminate analysis of data, phage typing techniques were shown to be a potential tool for tracing fecal contamination of groundwater.

Includes bibliographical references. The aim of this work is the further characterisation of the citrus exocortis viroid (CEV) replication complex in a tomato host system. The study employed three approaches. i. To raise polyclonal antiserum against a putative catalytic component of the CEV replication complex, the second largest subunit of tomato RNA polymerase II--ii. To develop a cell-free system for CEV RNA synthesis--iii. To use the polyclonal antiserum to the second largest subunit of RNA polymerase II, and a commercially available monoclonal antibody to the largest subunit, for antibody inhibition and immunoprecipitation experiments using the cell-free system.

<i>Rhizobium leguminosarum</i> are well known for their ability to fix nitrogen (N). In addition, their capacity to solubilize phosphate has been receiving attention in recent years. The work presented in this thesis examined two aspects of screening and evaluating dicalcium phosphate (Pi) (CaHPO4) solubilizing <i> R. leguminosarum</i>. The objectives of this study were to: 1) identify a medium that is sensitive and effective as a screening tool for phospahte solubilizing <i>R. leguminosarum</i>; 2) determine the effect of N and carbon (C) on growth and P solubilization of <i>R. leguminosarum</i> isolates; 3) determine the relationship between the ability to solubilize CaHPO4 by <i>R. leguminosarum</i> isolates on solid medium and in liquid broth of same composition; and 4) assess and compare the ability of <i>R. leguminosarum</i> isolates to solubilize different P sources in soil under growth chamber conditions.<p>In this study, 30 <i>R. leguminosarum</i> isolates were evaluated for phosphate solubilization in broth and solid formulations of three different media, Yeast Mannitol Extract (YEM), Botanical Research Institute Phosphate Nutrient medium (MNBRI) and Pikovskaya Phosphate medium (PVK). All media contain CaHPO4 as the only phosphorus (P) source. The <i>R. leguminosarum</i> isolates were selected on the basis of their different plasmid profiles, indicative of genetically distinct isolates. <p>All 30 isolates increased the Pi concentration in solution to varying degrees in liquid cultures but performance varied from one medium to another. The highest average solution Pi concentration achieved by the 30 <i>R. leguminosarum</i> isolates was obtained from PVK cultured broth. CaHPO4 solubilization by <i>R. leguminosarum</i> isolates in liquid was associated with a decrease in pH. Among the three tested media, the lowest pH by the thirty <i>R. leguminosarum</i> isolates was obtained in PVK. Ability of the isolates to solubilize CaHPO4 on the solid media was not comparable to the performance of the isolates grown in liquid because only fewer <i>R. leguminosarum</i> isolates showed visible P solubilization on the solid media.<p>The composition and formulation of medium influence the ability of the <i>R. leguminosarum</i> isolates to solubilize CaHPO4. Effects of N and C concentrations on the growth and CaHPO4 solubilization by nine <i>R. leguminosarum</i> isolates were examined in liquid formulation. Ammonium N had a greater influence on the growth and CaHPO4 solubilization by <i>R. leguminosarum</i> isolates than C at the tested levels. The growth of isolates was inhibited by ammonium N at 0.5 g L-1 as (NH4)2SO4 meaning there were less viable cells in this N concentration than were of ammonium N at 0.1 g L-1. The ability of isolates to solubilize Pi however was not affected by ammonium N at 0.5 g L-1 as (NH4)2SO4. The media containing low N (0.1 g (NH4)2S04 L-1) both Pi solubilization and growth of <i>R. leguminosarum</i> isolates were not affected.<p><i>R. leguminosarum</i> isolates were tested for their effects on growth and P uptake of canola plants in P-deficient soils amended with different P sources. <i>R. leguminosarum</i> isolates were selected separately based on their ability to solubilize CaHPO4 from the three screening media. A quadrant model was used based on the ability of the 30 <i>R. leguminosarum</i> isolates to solubilize CaHPO4 on both solid and liquid formulations within a medium. The effect of <i>R. leguminosarum</i> on canola dry mass, tissue Pi content and total Pi uptake varied from one isolate to another, but was not different from the controls. The quadrant model failed to correlate isolates able to solubilize CaHPO4 in laboratory screening to isolates able to solubilize P in the growth chamber. Despite the influence of the medium composition and formulation, none of tested media predicted Pi solubilization ability by the <i>R. leguminosarum</i> isolates in soils under growth chamber conditions, from their Pi solubilization of laboratory screenings. <p>The work of this thesis demonstrates that phosphate solubilization is a complex process that depends on both organism and soil. Growth condition is an important factor for a <i>R. leguminosarum</i> isolate to express its ability to solubilize CaHPO4. Liquid media screenings illustrate an isolates ability to solubilize CaHPO4 under nonstressful conditions, but solid media screenings demonstrate the P solubilization result of an isolate under more stressful conditions. The lack of relationship in P solubilization ability by <i>R. leguminosarum</i> isolates, between laboratory methods to soil test, means neither liquid or solid media can provide a definitive selection process. Additional parameters should be investigated to modify the soil bioassay protocols and ultimate selection procedures. These include pH conditions, isolate colonization, growth, and survival on plants and rhizosphere.

<i>Rhizobium leguminosarum</i> are well known for their ability to fix nitrogen (N). In addition, their capacity to solubilize phosphate has been receiving attention in recent years. The work presented in this thesis examined two aspects of screening and evaluating dicalcium phosphate (Pi) (CaHPO4) solubilizing <i> R. leguminosarum</i>. The objectives of this study were to: 1) identify a medium that is sensitive and effective as a screening tool for phospahte solubilizing <i>R. leguminosarum</i>; 2) determine the effect of N and carbon (C) on growth and P solubilization of <i>R. leguminosarum</i> isolates; 3) determine the relationship between the ability to solubilize CaHPO4 by <i>R. leguminosarum</i> isolates on solid medium and in liquid broth of same composition; and 4) assess and compare the ability of <i>R. leguminosarum</i> isolates to solubilize different P sources in soil under growth chamber conditions.<p>In this study, 30 <i>R. leguminosarum</i> isolates were evaluated for phosphate solubilization in broth and solid formulations of three different media, Yeast Mannitol Extract (YEM), Botanical Research Institute Phosphate Nutrient medium (MNBRI) and Pikovskaya Phosphate medium (PVK). All media contain CaHPO4 as the only phosphorus (P) source. The <i>R. leguminosarum</i> isolates were selected on the basis of their different plasmid profiles, indicative of genetically distinct isolates. <p>All 30 isolates increased the Pi concentration in solution to varying degrees in liquid cultures but performance varied from one medium to another. The highest average solution Pi concentration achieved by the 30 <i>R. leguminosarum</i> isolates was obtained from PVK cultured broth. CaHPO4 solubilization by <i>R. leguminosarum</i> isolates in liquid was associated with a decrease in pH. Among the three tested media, the lowest pH by the thirty <i>R. leguminosarum</i> isolates was obtained in PVK. Ability of the isolates to solubilize CaHPO4 on the solid media was not comparable to the performance of the isolates grown in liquid because only fewer <i>R. leguminosarum</i> isolates showed visible P solubilization on the solid media.<p>The composition and formulation of medium influence the ability of the <i>R. leguminosarum</i> isolates to solubilize CaHPO4. Effects of N and C concentrations on the growth and CaHPO4 solubilization by nine <i>R. leguminosarum</i> isolates were examined in liquid formulation. Ammonium N had a greater influence on the growth and CaHPO4 solubilization by <i>R. leguminosarum</i> isolates than C at the tested levels. The growth of isolates was inhibited by ammonium N at 0.5 g L-1 as (NH4)2SO4 meaning there were less viable cells in this N concentration than were of ammonium N at 0.1 g L-1. The ability of isolates to solubilize Pi however was not affected by ammonium N at 0.5 g L-1 as (NH4)2SO4. The media containing low N (0.1 g (NH4)2S04 L-1) both Pi solubilization and growth of <i>R. leguminosarum</i> isolates were not affected.<p><i>R. leguminosarum</i> isolates were tested for their effects on growth and P uptake of canola plants in P-deficient soils amended with different P sources. <i>R. leguminosarum</i> isolates were selected separately based on their ability to solubilize CaHPO4 from the three screening media. A quadrant model was used based on the ability of the 30 <i>R. leguminosarum</i> isolates to solubilize CaHPO4 on both solid and liquid formulations within a medium. The effect of <i>R. leguminosarum</i> on canola dry mass, tissue Pi content and total Pi uptake varied from one isolate to another, but was not different from the controls. The quadrant model failed to correlate isolates able to solubilize CaHPO4 in laboratory screening to isolates able to solubilize P in the growth chamber. Despite the influence of the medium composition and formulation, none of tested media predicted Pi solubilization ability by the <i>R. leguminosarum</i> isolates in soils under growth chamber conditions, from their Pi solubilization of laboratory screenings. <p>The work of this thesis demonstrates that phosphate solubilization is a complex process that depends on both organism and soil. Growth condition is an important factor for a <i>R. leguminosarum</i> isolate to express its ability to solubilize CaHPO4. Liquid media screenings illustrate an isolates ability to solubilize CaHPO4 under nonstressful conditions, but solid media screenings demonstrate the P solubilization result of an isolate under more stressful conditions. The lack of relationship in P solubilization ability by <i>R. leguminosarum</i> isolates, between laboratory methods to soil test, means neither liquid or solid media can provide a definitive selection process. Additional parameters should be investigated to modify the soil bioassay protocols and ultimate selection procedures. These include pH conditions, isolate colonization, growth, and survival on plants and rhizosphere.

Spores of thermophilic bacilli are a common concern during the manufacture of milk powder. Spores are believed to occur in high numbers in milk powder due to their ability to survive pasteurisation, attach to stainless steel surfaces, germinate, grow as biofilms and subsequently enter the product stream and thereby contaminate the final product. In this study, thirty one thermophilic bacilli isolates were obtained from a New Zealand milk powder production line and identified as either Anoxybacillus flavithermus or Geobacillus spp. using random amplified polymorphic DNA (RAPD) and species-specific PCR. Sporulation media and a polyethylene glycol two-phase separation system were modified to produce high yields of spores free from debris. The spores of four Geobacillus spp. isolates (CGT-8, D4, E7 and E11) were characterised in terms of structure (electron microscopy), surface charge (zeta potential), hydrophobicity (contact angle and microbial adhesion to hexadecane) and attenuated total reflectance infrared spectroscopy (ATR-IR). Spores from three of the four isolates possessed an exosporium while the fourth did not. However the integrity of the exosporium varied over time. The spores were negatively charged (-10 to -20 mV) at neutral pH and high ionic strength (0.1 M KC1). Both hydrophobicity assays revealed that the spores of the four isolates were relatively hydrophilic while ATR-IR revealed the spores' surfaces consisted of protein and polysaccharides. The influence of these spore characteristics on adhesion to a variety of substrata under high flow rates was examined using the extended Derjaguin, Landau, Verwey and Overbeek (XDLVO) theory. Spores generally attached in higher numbers to hydrophobic surfaces compared to hydrophilic surfaces, however this observation was more prevalent for isolate D4. This result indicated that a single mechanism could not describe the adhesion of spores from different strains. A series of glass surfaces with modified characteristics were produced in order to test the antifouling properties on the adhesion of D4 spores. Spores suspended in a high ionic strength medium (0.1 M KC1) attached in greater numbers (1 Log₁₀ CFU cm⁻�) to positively charged and hydrophobic surfaces compared with negatively charged and hydrophilic surfaces. A clean in place (CIP) procedure, reduced spore numbers on hydrophobic and hydrophilic surfaces by 1.5 and by 2.0 Log₁₀ CFU cm⁻�, respectively. When spores were suspended in milk, there was little difference in the number of spores attaching to the different surfaces (ie. 3.5 to 3.8 Log₁₀ CFU cm⁻�), and spore removal from surfaces via a CIP regime was unchanged (1.5 to 2.0 Log₁₀ CFU cm⁻� reduction) compared with spores that attached in simple 1:1 electrolyte media. The effects of a caustic wash on spore surface characteristics and adhesion was determined. There was a significant reduction in spore viability (2 Log₁₀ CFU mL⁻�) after a 30 min caustic wash at 65 �C in the current study, however surviving spores displayed a greater propensity to attach to stainless steel. Surface characterisation results revealed an increase in hydrophobicity and a greater negative charge on the spores' surface after treatment with NaOH. Surviving spores could potentially recontaminate sections of the plant which are cleaned with this recycled caustic wash solution, thereby seeding surfaces with spores at the beginning of the next processing run. In conclusion, while surfaces that reduce spore adhesion and enhance removal can be produced, exposure to complex solutions such as milk can reduce the anti-fouling effectiveness of such surfaces to spore adhesion.