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Typescript (photocopy) / xii, 149 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Soil Science, University of Adelaide, 1982

Orientador: Gelson Luis Adabo / Banca: Luis Geraldo Vaz / Banca: Ligia Antunes Pereira Pinelli / Banca: Ricardo Faria Ribeiro / Banca: Sicknan Soares da Rocha / Resumo: Este estudo teve por objetivo avaliar a topografia e a aderência de Streptococcus mutans na superfície do titânio após procedimentos que simularam 10 anos de uso de dentifrícios fluoretado e não-fluoretado. Corpos-de-prova na forma de discos (6 mm Ø X 4 mm) de Ti-6Al-4V (Grupo L, N = 36) e de titânio comercialmente puro (Ti cp, Grupo T, N = 36) foram polidos metalograficamente e subdivididos em seis subgrupos (n=6) de acordo com a imersão (I) ou escovação (E) em água destilada (A), água destilada + dentifrício não-fluoretado (D) ou água destilada + dentifrício fluoretado (1500 ppm, pH 6,3) (DF). Os discos dos subgrupos IA, ID e IDF permaneceram submersos em suas respectivas soluções durante 244 h ( 10 anos). A escovação dos discos dos subgrupos EA, ED e EDF foi realizada em uma máquina de escovação linear com escovas macias (244 h; 60 ciclos/min). A topografia superficial dos discos foi avaliada antes (pré-tratamento) e após (pós-tratamento) a imersão ou a escovação. Para tanto, os discos foram analisados em microscópio de força atômica (MFA), no qual foram obtidas imagens tri-dimensionais (3D) e valores de rugosidade média (Ra). Após os tratamentos, discos dos subgrupos IDF e EDF foram analisados em microscopia dispersiva de raios-X (EDX) para a identificação dos elementos químicos. No teste de aderência, os discos foram contaminados com cepa padrão de Streptococcus mutans (NTCC 1023) para determinação do número de unidades formadoras de colônia (UFC/mL) das bactérias aderidas. Para averiguação do padrão de aderência dos micro-organismos, os discos foram analisados em microscópio eletrônico de varredura (MEV). As comparações entre os subgrupos foram realizadas por meio da análise de variância (one way ANOVA) e teste de Tukey HSD (α=0,05). Os valores de Ra... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Titanium exposure to fluorides could degrade the metal surface, contributing to an increased roughness and providing additional sites to micro-organisms adhesion. The aim of this study was to contrasting titanium surface topography after procedures that simulated 10 years of brushing using toothpastes with or without fluoride. Ti-6Al-4V (Group L - N=36) and commercially pure titanium (cp Ti - Group T; N=36) disks (6mm Ø X 4mm) were mirror-polished and treated according to 6 subgroups (n=6) as a function of immersion (I) or brushing (B) using distilled water (W), distilled water + fluoride-free toothpaste (T) and distilled water + fluoride toothpaste (1,500 ppm; pH = 6.3) (FT). Specimens submitted to immersion were submerged in the vehicles without brushing for 244 h ( 10 years). For brushed specimens, procedures were carried out in a linear brushing machine with a soft-bristled toothbrush (244 h; 60 cycles/min). Surface topography was evaluated at baseline (pre-treatment) and post-treatment, using atomic force microscope in order to obtain three-dimensional (3D) images and mean roughness (Ra). IFT and BFT samples were analyzed under scanning electron microscope with dispersive spectrometer (EDX). For the adhesion test, the disks were contaminated with standard strain of S. mutans (NTCC 1023) and the adhesion was analyzed by the colony-forming unit counts (CFU/mL) of the adhered viable cell and by scanning electron microscopy (SEM) images. The subgroups were compared with one-way ANOVA and Tukey post-test (α=.05). Pre and post-treatment values of Ra were compared using the paired Student T test (α=.05). At baseline, there was no significant difference among the Ra values of L subgroups (p = .40), or among T subgroups (p = .99). No significant changes were seen after immersions... (Complete abstract click electronic access below) / Doutor

Thesis (M.Sc. (Microbiology)) -- Mahidol University, 1979. / Partial support by National Research Council.

>Magister Scientiae - MSc / Drug-resistant infections are a global health crisis and drastically hinder the treatment options to effectively combat disease. Today, natural products remain an important source of novel drug candidates. Micro-organisms, in addition to being a source of bioactive natural products, represent a sustainable source of these compounds. As the marine environment is largely underexplored, the oceans represent a potential source of novel NPs. This study aimed at the discovery of novel NPs from bacteria associated with novel marine invertebrate species endemic to the South African coast, including a sponge Spongia (Spongia) sp. 001RSASPN and a tunicate, Pseudodistoma africanum Millar, 1954. The methodology comprised of culture-dependent and culture-independent strategies. The former involved the isolation of bacteria associated with the invertebrate species and subsequent screening for anti-microbial activity against a panel of indicator strains including a multi-drug resistant E. coli strain. Anti-bacterial activity was detected in 6.1% and 4% of bacterial isolates from the sponge and tunicate isolates respectively. The culture-independent strategy involved the use of PCR to select bioactive strains likely to contain novel NRPS or PKS secondary metabolite pathways. An NRPS A- domain exhibiting low sequence identity (65%) to reference sequences in the NCBI database was amplified from isolate PE8-15, a strain belonging to the genus Bacillus. This predicted a novel NRPS pathway within this strain. In addition, this isolate exhibited the most diverse anti-microbial profile including anti-bacterial and anti-fungal activity (A.fumigatus ATCC 46645). Therefore, as the most promising candidate, the genome of PE8-15 was sequenced following which 10 secondary metabolite pathways including bacteriocins (5), NRPS (3), siderophore (1) and a terpene pathway were identified. The A-domain amplified from PE8-15 originated from Cluster 4, and NRPS pathway predicted to encode a lipopeptide. Lipopeptides are an important class of compounds with a range of industrial applications in the pharmaceutical, cosmetic as well as food industry. The identification of potentially novel secondary metabolite pathways from even well- studied groups of organisms demonstrates the importance of sequence-based methods in natural product discovery. Furthermore, this study highlights the South African coast as a rich source of microbial natural products and should be exploited further for drug discovery.

One of the factors that maintains fruit quality is its microbial flora. Fruit holds a natural non-pathogenic epiphytic microflora but can become contaminated with pathogenic microorganisms during export, causing either postharvest decay or possibly resulting in a food safety risk. In order to study microbial dynamics on fruit surfaces and the environment fruit moves through in the export chain, fruit washings were made, surfaces were sampled and total populations and diversities determined per cm2. Hygiene and safety levels for fruit export environments were hereby determined by sampling various points along the apple export chain, which included two farms and a harbour in South Africa and two harbours, two repacking facilities and two retail centres in Europe. In this first study of its kind, all the surfaces that were sampled exceeded the international standard for cleaning efficacy of food-processing equipment that is <5 cfu/cm2, while several areas exceeded the maximum acceptable index level of microbial air contamination of 22 cfu/h in food industries. Washing of containers on a harbour in South Africa did not have a significant impact on microbial populations. Regarding fruit quality, it was determined that apple microflora fluctuate throughout the export process and that postharvest pathogens that are known to cause great economic losses in the apple industry, proved to be of little significance in this investigation. The presence of six foodborne pathogens i.e. Shigella sonnei, Salmonella muenchen, Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Staphylococcus epidermidi/s was monitored throughout the chain. Of these, only S. aureus and E. coli were recorded, although pathogenicity was not confirmed for the latter. Staphylococcus aureus was found in containers and at a retail centre in Europe, and S. aureus and S. epidermidis were recorded on apple surfaces for the first time. Escherichia coli was present in great numbers in fruit washing water on a farm in South Africa. Since the standard for food premises is very stringent and perhaps inapplicable for fresh fruit handling and holding facilities, future research should include development of a more realistic hygiene standard for fresh fruit environments. / Dissertation (MSc(Agric) : Plant Pathology)--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

The lethal effect of ultraviolet (UV) light on microorganisms is well known and many studies have been undertaken into the effects of UV induced damage. Most of this work has been experimental; by comparison relatively little theoretical work has been undertaken to analyse the kinetics of the UV inactivation process, or to develop quantitative methodologies to support the experimental work. This paper presents a new and simple model for quantifying the photolysis rate. A theoretical study is also presented in this paper which quantifies photolysis rates for E. coli O26 and E. coli O157:H7. This study uses experimental data collected by Tosa and Hirata, and reveals the photolysis rate for E. coil O26 during the UV irradiation process to be 4.69 x 10(-3) m2 J(-1). By comparison, E. coli O157:H7 is much more susceptible to UV induced damage than E. coli O26, having a photolysis constant of only 2.09 x 10(-3) m2 J(-1).

A biological investigation of the apparently intimate and mutually relationship exist­ing between certain plant-like micro-organisms and certain insects. The literature of the subject is briefly re­viewed and discussed and a critical appraisal of previous work is made. A problem, the association of certain micro-organisms with two species of grain feeding wee­vils, is discussed in greater detail and a method of approach is proposed and analysed. Studies of the micro-organisms in vivo and in vitro are described in conjunction with investigations, by experimental techniques, of the associa­tion of the micro-organisms and the weevils. Findings are discussed and conclusions are presented. / Thesis / Doctor of Philosophy (PhD)

L’écotoxicité de nanoparticules de dioxyde de cérium (CeO2 NP) en milieu dulçaquicole a été évaluée à l’aide (i) d’essais monospécifiques standardisés et (ii) de chaînes trophiques expérimentales exposées en microcosme. Aucune toxicité n’a été observée chez Nitzschia palea et Chironomus riparius en conditions monopsécifiques. Une inhibition de croissance a été observée chez les amphibiens Xenopus laevis et Pleurodeles waltl., ainsi qu’une toxicité aiguë chez le xénope et une génotoxicité dose-dépendante chez le pleurodèle. Les expositions en microcosme ont mis en évidence une toxicité aiguë chez le pleurodèle, des modifications des communautés bactériennes, une diminution de la décomposition de la litière, ainsi que des effets tératogènes chez le chironome. Les effets observés varient suivant la nature des CeO2 NP étudiées. L’utilisation d’un système biologique complexe permet l’étude des mécanismes de toxicité dans des conditions plus représentatives des conditions environnementales. / The ecotoxicity of cerium dioxide nanoparticles (CeO2 NPs) was studied on freshwater organisms (i) in standardized monospecific conditions and (ii) on experimental trophic chains exposed in microcosms. No toxicity was observed on Nitzschia palea and Chironomus riparius in monospecific conditions. Growth inhibition was observed on the amphibian species Xenopus laevis and Pleurodeles waltl., as well as acute toxicity and dose-dependent genotoxicity observed on Xenopus and Pleurodeles, respectively. Microcosm experiments revealed acute effects on Pleurodeles, changes in bacterial communities, a decrease in leaf litter decomposition and teratogenicity on chironomids. The observed effects vary depending on the type of CeO2 NPs. The use of complex biological system enables the study of toxicity mechanisms in environmentally relevant conditions.

O presente trabalho teve por objetivo realizar experimentos de incorporação de precursores isotopicamente marcados em produtos naturais isolados do meio de cultura de duas espécies de fungos do gênero Penicillium, de maneira a se verificar a rota de biossíntese dos compostos produzidos pelas linhagens P. citrinum F53 e P. oxalicum F30. Para tanto, os meios de cultura utilizados na fermentação das linhagens foram enriquecidos com os seguintes precursores: [1-13C1]acetato de sódio, [1,2-13C2]acetato de sódio, [2,3-13C2]propionato de sódio, [metil-13C1]metionina, [1-13C1]glicose, [U-13C5]ornitina, [U-13C6]lisina, [U-13C5]prolina, [U-13C6]histidina, [2-indol-13C1]triptofano e [U-13C6]ácido antranílico, separadamente. Ao final do período de fermentação, as culturas foram separadamente submetidas à extração em fase sólida e analisadas por CLAE/UV/EM/IES. Os experimentos de incorporação que apresentaram resultados positivos tiveram seus produtos purificados por CLAE/UV e analisados por RMN de 13C. Os resultados obtidos mostraram que dois dihidropirrois produzidos por P. citrinum F53 são formados por uma rota biossintética mista, oriunda de um resíduo de ornitina, um grupo metila derivado da metionina e uma cadeia policetídica derivada do acetato. Os alcaloides citrinalina B e 17-hidroxicitrinalina B, também produzidos por P. citrinum F53, são ambos derivados de dois resíduos de aminoácidos, ornitina e triptofano (via ácido antranílico), e dois grupos isopreno derivados da glicose (via mevalonato). Os alcaloides oxalina e meleagrina, produzidos por P. oxalicum F30, são formados a partir de uma via biossintética mista derivada de dois resíduos de aminoácidos, histidina e triptofano (via ácido antranílico), e grupos metila derivados da metionina. / The present investigation aimed to carry out feeding experiments for the incorporation of isotopic labeled precursors on natural products isolated from the culture media of two fungal species belonging to the Penicillium genus, in order to verify the biosynthetic pathway of the compounds produced by the P. citrinum F53 and P. oxalicum F30 fungal strains. Culture media used in the fermentation of the fungal strains were enriched with the following isotopic labeled precursors: [1-13C1]sodium acetate, [1,2-13C2]sodium acetate, [2,3-13C2]sodium propionate, [methyl-13C1]methionine, [1-13C1]glucose, [U-13C5]ornithine, [U-13C6]lysine, [U-13C5]proline, [U-13C6]histidine, [2-indol-13C1]tryptophan, and [U-13C6]anthranilic acid, separately. At the end of the fermentation period, culture media were separately subjected to solid phase extraction and analyzed by LC/UV/ESI/MS. The incorporation experiments that showed positive results were purified by HPLC/UV, and the pure compounds labeled in different positions were then analyzed by 13C-NMR. The results demonstrated that two dihydropyrroles produced by P. citrinum F53 were formed via a mixed biosynthetic route, derived from ornithine, a methyl group derived from methionine, and a polyketide chain derived from acetate. The alkaloids citrinalin B and 17-hydroxycitrinalin B, also produced by P. citrinum F53, are both derived from two amino acid residues, ornithine and tryptophan (via anthranilic acid), and two isoprene units derived from glucose via the mevalonate pathway. The alkaloids oxaline and meleagrine, produced by P. oxalicum F30, are formed via a mixed biosynthetic pathway by two amino acid residues, histidine and tryptophan (via anthranilic acid), and methyl groups derived from methionine.