Thesis (doctoral)--Kaiser-Wilhelms-Universität Strassburg, 1902? / Includes bibliographical references (p. 68-72).

No description available.

The Gram-positive bacterium, Rhodococcus sp. 33, was selected for further study to identify the characteristics conferring it with high tolerance to concentrations of benzene. Since most organic solvents, like benzene, are lipophilic, they tend to accumulate within lipid membranes where they express toxicity. The mechanisms conferring this Rhodococcus with resistance to benzene were hypothesised to be located within the subcellular region of this bacterium - cell wall, membrane, and cell-bound polymer. Therefore, this investigation was instigated to identify these mechanisms. To accomplish this, the development of methodologies to isolate highly purified cell wall and membrane fractions, from the organism, were required. To corroborate this investigation, a total of 6 benzene-sensitive mutants were prepared from Rhodococcus sp. 33 and their characteristics compared to those of the parent wild-type strain. 1-D PAGE analysis of proteins revealed various benzene-induced wall, membrane, and cytoplasmic proteins in the w-t. A protein band, with an approximate molecular weight of 58 kDa, was identified to be absent in the most sensitive mutant isolated (mutant M2b). Interestingly, much of this research showed that the benzene-catabolising enzymes played an insignificant role in tolerating the benzene. Gas chromatography and mass spectrometry of whole cell-derived fatty acids revealed that benzene induced an increase in the ratios of saturated/unsaturated fatty acids. Moreover, protein determinations revealed that benzene induced an increase in the concentration of total membrane protein. These increases are suggestive as possible mechanisms to decrease the fluidity of the cell membrane. This was further supported by the observed increase in the generalised polarisation (GP) of laurdan fluorescence in the membranes during growth of the organism with benzene, which is correlated with a decrease in membrane fluidity. The organism was also found to synthesise hexadecenoic acid, 16:1w6c (11 - 13% of total fatty acids), an uncommon fatty acid and previously unreported in other Rhodococcus spp. Analysis of the organism's cell-bound extracellular polymer revealed it to be composed of polysaccharide with biosurfactant-like properties. Its function is proposed to act as a surfactant layer outside the cell, concentrating the benzene within its matrix and reducing benzene's contact with the cell membrane.

No description available.

The Gram-positive bacterium, Rhodococcus sp. 33, was selected for further study to identify the characteristics conferring it with high tolerance to concentrations of benzene. Since most organic solvents, like benzene, are lipophilic, they tend to accumulate within lipid membranes where they express toxicity. The mechanisms conferring this Rhodococcus with resistance to benzene were hypothesised to be located within the subcellular region of this bacterium - cell wall, membrane, and cell-bound polymer. Therefore, this investigation was instigated to identify these mechanisms. To accomplish this, the development of methodologies to isolate highly purified cell wall and membrane fractions, from the organism, were required. To corroborate this investigation, a total of 6 benzene-sensitive mutants were prepared from Rhodococcus sp. 33 and their characteristics compared to those of the parent wild-type strain. 1-D PAGE analysis of proteins revealed various benzene-induced wall, membrane, and cytoplasmic proteins in the w-t. A protein band, with an approximate molecular weight of 58 kDa, was identified to be absent in the most sensitive mutant isolated (mutant M2b). Interestingly, much of this research showed that the benzene-catabolising enzymes played an insignificant role in tolerating the benzene. Gas chromatography and mass spectrometry of whole cell-derived fatty acids revealed that benzene induced an increase in the ratios of saturated/unsaturated fatty acids. Moreover, protein determinations revealed that benzene induced an increase in the concentration of total membrane protein. These increases are suggestive as possible mechanisms to decrease the fluidity of the cell membrane. This was further supported by the observed increase in the generalised polarisation (GP) of laurdan fluorescence in the membranes during growth of the organism with benzene, which is correlated with a decrease in membrane fluidity. The organism was also found to synthesise hexadecenoic acid, 16:1w6c (11 - 13% of total fatty acids), an uncommon fatty acid and previously unreported in other Rhodococcus spp. Analysis of the organism's cell-bound extracellular polymer revealed it to be composed of polysaccharide with biosurfactant-like properties. Its function is proposed to act as a surfactant layer outside the cell, concentrating the benzene within its matrix and reducing benzene's contact with the cell membrane.

Thesis (Ph. D.)--University of New South Wales, 1999. / Also available online.

Thesis (Ph. D.)--Lehigh University, 1997. / Includes vita. Bibliography: leaves 87-91.

Thesis (Ph. D.)--Dundee College of Technology, 1981. / Bibliography: leaves 357-416.

Made available in DSpace on 2015-07-08T12:28:18Z (GMT). No. of bitstreams: 2 4.pdf: 1791166 bytes, checksum: e18bbf1db8c3f87f4338a15297302f69 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2014 / Fundação Oswaldo Cruz. Instituto Nacional de Controle de Qualidade em Saúde / Casos de infecções invasivas por corinebactérias, colonizadoras do ambiente e da microbiota humana ou de animais, tem sido crescentes em decorrência de melhor sobrevivência de indivíduos imunocomprometidos. Além da fenotipagem, métodos moleculares tem sido fundamentais na identificação de bastonetes Gram positivos irregulares(BGPI). O presente estudo teve como objetivo a caracterização fenotípica e genotípica de estirpes de corinebactérias isoladas de sítios intravenosos de pacientes internados em um hospital universitário no Rio de Janeiro. Neste sentido, 60 estirpes de microrganismos Gram positivos foram analisadas por metodologia enotípica convencional, sistemas API Coryne e Vitek 2 (bioMérieux) e análise das sequências dos genes 16S rRNA e rpoB, utilizada como metodologia de referência para avaliação dos sistemas fenotípicos. Os dados indicaram o isolamento de Corynebacterium striatum (44,68 %), Corynebacterium amycolatum (31,91 %), Corynebacterium jeikeium (8,51 %), Corynebacterium urealyticum (6,39 %), Corynebacterium diphtheriae (4,26%), Corynebacterium simulans (2,12%) e Corynebacterium minutissimum (2,12%) do sangue de pacientes fazendo o uso ou não de dispositivos invasivos. As espécies predominantes C. striatum e C. amycolatum apresentaram 8 e 9 perfis de resistência aos agentes antimicrobianos, respectivamente. O perfil de resistência com sensibilidade apenas à tetraciclina, linezolida e vancomicina, foi prevalente durante um surto epidêmico de C. striatum ocorrido em 2010. Este mesmo perfil foi observado para C. amycolatum, C. jeikeium e C. urealyticum. A identificação definitiva da maioria das estirpes de C. striatum, C. amycolatum, C. jeikeium, C. simulans e C. minutissimum só foi possível pela genotipagem. Interessantemente, a análise das sequências do gene 16S rRNA permitiu a identificação de outros microrganismos como Abiotrophia defectiva (6,67%), Arthrobacter (1,67%), Brevibacterium (11,67%) e Microbacterium (1,67%). / Cases of invasive infections corynebacteria , colonizing the environment and human and animal microbiota, has been increasing due to better survival of immunocompromised individuals. Besides phenotyping, molecular methods have been of great value in the identification of Gram positive irregular rods (BGPI). The present study aimed to phenotypic and genotypic characterization of isolates from corynebacteria isolated of intravenous sites of patients at a university hospital in Rio de Janeiro. Thus, 60 isolates of Gram positive microrganisms were analyzed by conventional phenotype methodology, and Vitek and API Coryne 2 systems (bioMérieux) and by sequence analysis of 16S rRNA and rpoB genes. The genotypic identification was used as reference methods for evaluation of phenotypic systems. The data indicated the isolation of Corynebacterium striatum (44,68 %), Corynebacterium amycolatum (31,91 %), Corynebacterium jeikeium (8,51%), Corynebacterium urealyticum (6,39 %), Corynebacterium diphtheriae (4,26%), Corynebacterium simulans (2.12%) and Corynebacterium minutissimum (2,12%) from the blood of patients making use or not of invasive devices. The predominant species C. striatum and C. amycolatum presented 8 and 9 profiles of resistance to antimicrobial agents, respectively. The resistance profile with sensitivity just to tetracycline, linezolid and vancomycin, was prevalent during an outbreak of C. striatum occurred in 2010. The same profile was observed for C amycolatum, C. jeikeium and C. urealyticum. The definitive identification of most strains of C. striatum, C. amycolatum, C. jeikeium, C. simulans and C. minutissimum was possible only by genotyping . Interestingly, the sequence analysis of the 16S rRNA gene allowed the identification of other microorganisms such as Abiotrophia defectiva (6,67%), Arthrobacter (1,67 %), Brevibacterium (11.67 %) and Microbacterium (1.67 %). In conclusion, BGPI isolates from invasive infections should not be neglected and sequence analysis of 16S rRNA and rpoB genes can contribute to the definitive identification of the species of Gram positive microorganisms, including corynebacteria involved in these infections.

published_or_final_version / Dentistry / Master / Master of Dental Surgery