Mycoplasmas conform most closely with the theoretical concept of 'minimum cells', existing as the smallest, free-living organisms capable of self-replication. They survive as parasites of plants, insects, animals or humans, with the most common human colonising species being Mycoplasma hominis. M. hominis has been characterised as a human pathogen responsible for a variety of infections, which pose a significant threat particularly to immunocompromised patients and neonates. However little has been elucidated about the cell physiology and molecular structure of this organism. Of interest to this study were the investigation of the heat shock response of M. hominis and the diagnostic assays used for its detection. The heat shock response is a ubiquitous physiological feature of all organisms and displays unprecedented conservation. This phenomenon is particularly evident in the 70 kDa family of heat shock proteins (hsp70) which exhibits a high degree of homology between different species. The hsp70 gene from M. hominis was cloned and preliminary partial sequencing indicated the similarity with other hsp70 homologs. The regulation of hsp70 expression at the transcriptional and translational levels was investigated. The level of hsp70 mRNA was found to increase correspondingly in response to heat shock, more visibly than the level of hsp70 protein. However imrnunochemical studies of the M. hominis hsp70 translation product demonstrated further the homology with other species. To facilitate rapid diagnosis of M. hominis infections, a PCR ELISA diagnostic assay was developed and optimised. The amplification of a conserved region of the M. hominis 16S rRNA gene was linked to subsequent hybridisation to an appropriate capture probe in a microtiter plate format. The sensitivity of the assay was comparable to other molecular assays although the PCR ELISA produces more rapid results and is less labour intensive. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

The increasing frequency of enterococci as a major cause of nosocomial infections and the transmission of these organisms amongst hospital patients demands a greater awareness of the Enterococcus. Therapy of enterococcal infections is complicated by the pathogens continually changing resistance patterns to many broad-spectrum antibiotics. In addition, the ability of enterococci to cause serious invasive infections including endocarditis and septicaemia with associated high mortality rates; prompted this study which was aimed at identifying the biological properties of enterococci isolated from blood cultures of patients admitted at King Edward VIII hospital, Durban. Enterococci were identified to species level by the API 20 Strep system which identified 68% and a conventional biochemical system of Facklam and Collins which identified 100% of the isolates.The emergence of beta-Iactamase producing enterococci in other countries encouraged the testing of all isolates for this enzyme. All were beta-Iactamase negative. The reported false susceptibility for aminoglycosides and cephalosporins with blood enriched media encouraged the testing of these antibiotics with and without the supplementation of 5% lysed blood. The results showed that an average false susceptibility of 55 % occurred for gentamicin and 35% for tobramycin and netilmicin. The cephalosporins affected, cefotaxime and cefuroxime showed a false susceptibility of 28% and 17% respectively. The choice of treatment for serious enterococcal infections is a syllergistic combination of a beta-Iactam antibiotic plus an aminoglycoside for enterococci with intrinsic low-level resistance. The development of high-level aminoglycoside resistance, MIC 22000,ug/ml results in loss of synergism. This study showed that 26.4 % of enterococcal isolates displayed high level aminoglycoside resistance i.e. to gentamicin and streptomycin. Time-kill study showed reduced killing rate for these organisms for the beta-Iactams and glycopeptides with low-level gentamicin resistance. The results confirmed that a cell-wall active agent combined with gentamicin can be successfully used for enterococcal therapy if the organism has intrinsic low-level resistance to this amino glycoside. Pulsed-field gel electrophoresis (PFGE) carried out on a selected number of Enterococcus faecalis and Enterococcus faecium with high-level aminoglycoside resistance showed a variability in the restriction endonucelase digestion patterns. This suggests independent development of high-level gentamicin resistance and not clonal expression. The ease and reliability with which enterococcal isolates may be typed using this technique to compare different strains represent a significant advance. / Thesis (M.Med.Sc.)-University of Natal, 1999.

During fermentation, the yeast Saccharomyces cerevisiae produces a broad range of aroma-active esters that are important for the desirable complex flavour of beer. The sensory threshold levels of these esters in beer are low, ranging from 0.2 ppm for isoamyl acetate to 15-20 ppm for ethyl acetate. Although esters are only present in trace amounts in beer, they are extremely important as minor changes in their concentration may have dramatic effects on beer flavour. Therefore, optimization of the concentrations of these aroma-active esters in beer is of interest in beer brewing. The number and concentration of esters in beer may be influenced by the fermentation parameters, nutritional composition of fermentation medium and yeast strain type. Therefore, this study investigated the influence of fermentation temperature, pH, and wort nutritional supplements (amino acids and zinc) on the production of yeast-derived ester compounds. In addition, the overall fermentation performance was evaluated based on the reducing sugar and Free Amino Nitrogen (FAN) utilization, ethanol production and yeast cell density. These parameters were analysed using the Dinitrosalicyclic acid method, Ninhydrin assay, Gas Chromatography and standard spread plate technique. The concentration and stability of ethyl acetate, isoamyl acetate, phenyl ethyl acetate, ethyl hexanoate, ethyl decanoate and ethyl octanoate was monitored during storage at 4 °C and room temperature (RT), in the final beer by Chromatography. The expression levels of the ester synthetase genes under conditions that resulted in the highest increase in ester production were quantified by Real-Time PCR. For the lager beer, the best fermentation performance was achieved at RT (±22.5°C), resulting in the utilization of the highest amount of nutrients and production of 4.86% (v/v) ethanol. This was accompanied by the highest production of acetate and ethyl esters, which were 40.86% and 87.21%, respectively, higher than that of the control. Spent yeast density ranged from 2.492 to 3.358 mg/ml for all parameters tested, with the highest yield produced when wort was supplemented with 0.120 g/l zinc sulphate. Fermentations at 14 °C yielded the highest foam head stability and spent yeast viability with a foam head rating of 2.67 and a spent yeast viability of 3.85 × 107 cfu/ml. Ester compounds were relatively stable at 4 °C than at room temperature decreasing by only 7.93% after three months. Of all the volatile esters produced, ethyl decanoate was the least stable, with a 36.77% decrease in concentration at room temperature. For the ale beer, the best fermentation performance which resulted in the highest nutrient utilization was achieved when wort was supplemented with 0.75 g/l L-leucine resulting in the utilization of the highest amount of nutrients (51.25% FAN and 69.11% reducing sugar utilization) and production of 5.12% (v/v) ethanol. At the optimum fermentation pH of 5, 38.27% reducing sugars and 35.28% FAN were utilized, resulting in 4.32% ethanol (v/v) production. Wort supplemented with 0.12 g/l zinc sulphate resulted in 5.01% ethanol (v/v) production and 54.32% reducing sugar utilization. Spent yeast density ranged from 1.985 to 2.848 mg/ml for all parameters tested with the highest yield produced when wort was supplemented with 0.120 g/l zinc sulphate. This was also accompanied by the highest yeast viability of 2.12 × 107 cfu/ml achieved on day 3 of fermentation. Supplementation with 0.75 g/l L-leucine yielded the highest foam head stability with a rating of 2.67. Overall, ester compounds were relatively more stable at 4 °C than at RT decreasing by only 6.93% after three months, compared to a decrease of up to 16.90% observed at RT at the same time. Of all the volatile esters produced, ethyl octanoate was the least stable, with a 32.47% decrease in concentration at RT, phenyl ethyl acetate was the most stable ester at RT, decreasing by 9.82% after three months. Wort supplemented with 0.75 g/l L-leucine resulted in an increase in isoamyl acetate and phenyl ethyl acetate production by 38.69% and 30.40%, respectively, with a corresponding high expression of alcohol acetyltransferases, ATF2 (133.49-fold higher expression than the control). Elevation of fermentation temperature to RT resulted in the upregulation of ATF2 (27.11-fold), and producing a higher concentration of isoamyl acetate. These findings indicate that ester synthesis during fermentation is linked to both substrate availability and the regulation of gene expression. Therefore, it would be possible to manipulate the expression of certain ester synthestase genes to create new yeast strains with desirable ester production characteristics. Results from this study also suggest that supplementing wort with essential nutrients required for yeast growth and optimizing the fermentation conditions could be effective in controlling aroma-active ester concentrations to a desired level in beer. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

Eucalyptus, pine and wattle are the predominant exotic wood species used in the production of dissolving pulp in South Africa. On entering the mill, wood is chipped and stored in outdoor piles where it becomes vulnerable to microbial degradation and spontaneous combustion. Major losses of stored chips are due to high temperatures and combustion caused by heat energy released by microbial fermentation. Changes in the chemistry of the wood chips caused by the metabolic activity of indigenous microflora combined with the inherent chemical characteristics of each wood species could have a potential impact on final pulp quality and yield. Therefore the objective of this study was to analyse the microbial (bacteria and fungi) communities present in commercial wood chip piles and correlate this with changes in the chemistry of the wood in summer and winter. The molecular fingerprinting technique of Denaturing Gradient Gel Electrophoresis (DGGE) was optimized for the detection of microbial diversity in commercial wood chips. Wood chips were collected from an industrial wood yard and milled to different specifications. A total of four primer sets with GC-clamps were tested in nested PCR for DGGE analysis. 16S and 18S rRNA genes were amplified using 338f-GC/518r; 933F-GC/1387R (bacteria) and NS26/518R-GC; EF4F/518R-GC (fungi), respectively. Several gel gradients were examined to determine optimal separation of bacterial (40/60%, 35/50%, 30/60%) and fungal (35/50%, 20/45%, 25/50%) PCR-DGGE products. Comparison of the DGGE profiles revealed greater diversity in the milled wood chips amplified using primer sets; 338F-GC/518R (16S) and NS26/518R-GC (18S) with gradients of 30/60% (16S) and 25/50% (18S). Once optimized, this standardized protocol was tested against five samples to assess its applicability to woodyard samples. 16S and 18S DGGE profiles were generated and amplicons excised from gels, re-amplified, sequenced and the microorganism from which the DNA originated was determined. In the second phase a cross-sectional study of wood chip piles from a commercial dissolving pulp mill was conducted with sample collected in summer and winter using the optimized PCR-DGGE technique. Microbial strains were identified after sequencing of 16S and 18S rRNA amplicons separated by DGGE. Chemical characteristics of the wood chips were evaluated by conducting extractive analyses using HPLC. Due to unpredictable combinations of different wood species in commercial wood chip piles, the third phase involved the investigation of individual Eucalyptus species. The microflora indigenous to the two Eucalyptus species (E. dunnii and E. nitens) and a combination of the two were subjected to winter and summer simulations for one month during which samples were tested for wood chemistry properties, microflora and the final samples were used to generate dissolving pulp. Using the PCR-DGGE method eighteen bacterial and twelve fungal species were identified from the five samples collected from the commercial wood chip pile, compared to the ten bacterial and nine fungal isolates which were identified using the culturing technique and standard 16S and 18S rRNA gene sequence analysis. Predominant genera in the optimization phase of this study were Klebsiella spp. (×3), Bacillus spp. (×2), Pantoea spp. (×2), Pseudomonas spp. (×2) and Paecilomyces spp. (×2). Application of the optimized DGGE technique to samples collected from the commercial pulping mill in summer and winter revealed variable profiles indicating a range of bacterial and fungal strains that varied in intensity in the areas and seasons sampled. Seventy nine (45 in summer and 34 in winter) and 29 (20 in summer and 9 in winter) distinct amplicons representing bacteria and fungi, respectively, were visualized. Predominant genera in summer were Pantoea rodasii, Inquilinus limosus, Streptococcus sp., Klebsiella spp., Diversispora sp., Boletaceae sp., Scutellospora sp., and Ophiostoma bicolour. In winter the prevailing genera were Leuconostoc palmae, Streptococcus sp., Bacillus spp., Diversispora sp., Boletaceae sp., and Bullera sp. Lower cellulose levels in summer correlated significantly with high microbial loads and the predominance of Bacillus spp., suggesting that in warm humid environments storage should not exceed 1-2 weeks. No correlations were determined between the decreased hot water levels in winter and microbial activity, however they were correlated to increased exposure of those samples to environmental factors. Chemistry data on the wood chips imparts the quality of the wood which only permitted projection of final pulp quality. This inadequacy was addressed in the third phase which included identification of microbial strains, originating from the individual Eucalyptus species, after sequencing of 16S and 18S rRNA amplicons separated by DGGE. Fungal and bacterial species were also isolated, cultured, identified and screened for lignocellulolytic enzyme activity. Ninety two and 88% of the fungi isolated were capable of producing cellulase and xylanase, respectively. Significant correlations exist between the microflora, seasons (greater diversity and loading in summer) and the chemical and physical properties of wood chips (lower cellulose and viscosity in summer) as well as Eucalyptus species (significantly higher cellulose and viscosity for the combination and E. nitens). Indigenous microflora of each wood species may be one of the contributing factors to poor/good pulp quality, as significant correlations were made between enzyme production of microorganisms and wood chemistry which ultimately has an impact on the final pulp quality and yields. This investigation provides proof of concept that combining wood species with different deterioration rates results in an overall improvement in pulp quality and thus paves the way for a practical and applicable approach to managing quality of chips. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.

Darbo tikslas: įvertinti Lietuvos rinkoje esančių razinų mikrobinę taršą. Tyrimo objektas: buvo tiriamos šešių skirtingų gamintojų (importuotojų) Sultana rūšies razinos. Iš viso surinkti 42 razinų mėginiai, iš kurių 28 mėginiai buvo paimti iš supakuotų razinų ir 14 razinų mėginiai sudarė sveriamos razinos. Mielių ir pelėsinių grybų skaičiui (KSV/g) nustatyti naudotas YGC (Yeast Extract Glucose Chloramphenicol) agaras. E.coli auginimui naudota chromogeninė terpė Chromocult coliform agar. Visuose tirtų skirtingų gamintojų (importuotojų) razinų mėginiuose buvo aptikta mielių ir pelėsinių grybų tarša. / The aim of work: to analyze micriobiological contamination in raisins of Lithuanian market. The object of work: six different Sultana raisin producers were examined. 42 samples were collected, 28 were collected from packed raisins and 14 from unpacked. YGC (Yeast Extract Glucose Chloramphenicol) agar was used to count yeasts and molds number. For E. coli identification was used Chromocult coliform agar. In every raisin sample yeasts and molds were identified.

Extreme environments created through natural and anthropogenic processes harbor microbes with diverse physiologies capable of catalyzing chemical reactions which are environmentally beneficial on local and global scales. This work focused on two unique environments, the Gulf of Mexico (GoM) submarine mud volcano systems and the subsurface soils at the Department of Energy s (DOE) Field Research Center (FRC) located in the Oak Ridge National Laboratory Reservation (Oak Ridge, TN). In addition to the physical and chemical extremes present within mud volcano sediments and FRC subsurface soils, these environments are sources of greenhouse gases as well as metal/radionuclide contaminants, respectively. Within the previously uncharacterized mud volcano cold seep sediments, culture-independent analyses of microbial community structure via DNA and RNA clone libraries indicated Gammaproteobacteria and anaerobic methane oxidizing Archaea as the dominant methane oxidizing taxa. Culture-dependent studies of FRC subsurface Arthrobacter and Bacillus isolates demonstrated extensive lateral gene transfer of the PIB-type ATPase metal resistance genes. Additionally, FRC Bacillus and Rahnella isolates demonstrated U(VI) sequestration capabilities as up to 95% soluble U(VI) was immobilization via biogenic phosphate mineral production resulting from constitutive nonspecific phosphohydrolase activity. Findings from these studies identify the prokaryotic diversity within aquatic and terrestrial sediments that contribute to the geochemical cycling of carbon, metals, and radionuclides.

Includes bibliography / xiii, 126 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.)--University of Adelaide, 1989

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Lic.-avh. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 2 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2010. / Härtill 5 uppsatser.