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51.
Bareetseng AS Kock JL Pohl CH Pretorius EE Botes PJ Van Wyk PW Nigam S 《Canadian journal of microbiology》2005,51(1):99-103
Immunofluorescence microscopy exposed the presence of novel 3-hydroxy oxylipins on the surfaces of aggregated hat-shaped ascospores of Ascoidea africana. These compounds were confirmed by gas chromatography - mass spectrometry analysis. Only the complete structure of a novel 3-hydroxy 10:1 could be determined. 相似文献
52.
Isolates representing Cryptococcus laurentii and Cryptococcus podzolicus, originating from soil of a heathland indigenous to South Africa, were screened for the presence of enantioselective epoxide hydrolases for 2,2-disubstituted epoxides. Epoxide hydrolase activity for the 2,2-disubstituted epoxide (+/-)-2-methyl-2-pentyl oxirane was found to be abundantly present in all isolates. The stereochemistry of the products formed by the epoxide hydrolase enzymes from isolates belonging to the two species (11 isolates representing C. laurentii and 23 isolates representing C. podzolicus) was investigated. The enantiopreferences of the epoxide hydrolases for 2,2-disubstituted epoxides of these two species were found to be opposite. All strains of C. laurentii preferentially hydrolysed the (S)-epoxides while all C. podzolicus isolates preferentially hydrolysed the (R)-epoxides of (+/-)-2,2-disubstituted epoxides. These findings indicate that the stereochemistry of the products formed from 2,2-disubstituted epoxides by the epoxide hydrolase enzymes of these yeasts should be evaluated as additional taxonomic criterion within the genus Cryptococcus. Also, the selectivity of some epoxide hydrolases originating from isolates of C. podzolicus was high enough to be considered for application in biotransformations for the synthesis of enantiopure epoxides and vicinal diols. 相似文献
53.
BackgroundEmpirical studies and population-level policy simulations show the importance of voluntary medical male circumcision (VMMC) in generalized epidemics. This paper complements available scenario-based studies (projecting costs and outcomes over some policy period, typically spanning decades) by adopting an incremental approach—analyzing the expected consequences of circumcising one male individual with specific characteristics in a specific year. This approach yields more precise estimates of VMMC’s cost-effectiveness and identifies the outcomes of current investments in VMMC (e.g., within a fiscal budget period) rather than of investments spread over the entire policy period.Methods/FindingsThe model has three components. We adapted the ASSA2008 model, a demographic and epidemiological model of the HIV epidemic in South Africa, to analyze the impact of one VMMC on HIV incidence over time and across the population. A costing module tracked the costs of VMMC and the resulting financial savings owing to reduced HIV incidence over time. Then, we used several financial indicators to assess the cost-effectiveness of and financial return on investments in VMMC. One circumcision of a young man up to age 20 prevents on average over 0.2 HIV infections, but this effect declines steeply with age, e.g., to 0.08 by age 30. Net financial savings from one VMMC at age 20 are estimated at US$617 at a discount rate of 5% and are lower for circumcisions both at younger ages (because the savings occur later and are discounted more) and at older ages (because male circumcision becomes less effective). Investments in male circumcision carry a financial rate of return of up to 14.5% (for circumcisions at age 20). The cost of a male circumcision is refinanced fastest, after 13 y, for circumcisions at ages 20 to 25. Principal limitations of the analysis arise from the long time (decades) over which the effects of VMMC unfold—the results are therefore sensitive to the discount rate applied, and more generally to the future course of the epidemic and of HIV/AIDS-related policies pursued by the government.ConclusionsVMMC in South Africa is highly effective in reducing both HIV incidence and the financial costs of the HIV response. The return on investment is highest if males are circumcised between ages 20 and 25, but this return on investment declines steeply with age. 相似文献
54.
Sporangiospores of Mucor circinelloides f. circinelloides CBS108.16 could germinate and grow on a wide variety of carbon sources in synthetic liquid media. Growth was supported by aldoses which have the same configuration at carbon atom number two as glucose. Di- and trisaccharides consisting of D-glucopyranosyl moieties were assimilated, while polysaccharides like inuline and starch were also utilised. Various alcohols and organic acids could be assimilated, while the phenolic compounds tested could not support aerobic growth. The fungus was able to ferment carbohydrates consisting of D-glucopyranosyl moieties, grow in the absence of vitamins and in the presence of cycloheximide. It also liquefied gelatin and produced lipases and cellulolytic enzymes. It was found that the highest percentages polyunsaturated fatty acids were produced when acetic acid, glucose, mannitol, soluble starch or trehalose was used as carbon source. The absence of vitamins in the medium lowered the percentage of these fatty acids. 相似文献
55.
Adine Oosthuizen Johan L. F. Kock Piet. J. Botes Pieter M. Lategan 《Applied microbiology and biotechnology》1987,26(1):55-60
Summary The cellular long-chain fatty acids of 69 strains of yeasts, representing 29 species associated with the brewing industry, were extracted by saponification and analyzed asmethyl esters by gas chromatography. The strains were characterized by the presence of palmitic, palmitoleic, stearic, oleic, linoleic and linolenic acid as the major fatty acids. The strains were divided into six groups on the basis of their fatty acid content. With this method it was possible to differentiate between the yeasts on species and, in some instances, on strain level. 相似文献
56.
Snake venom toxins. The amino acid sequences of toxins and from Naja nivea venom and the disulfide bonds of toxin 总被引:4,自引:0,他引:4
D P Botes 《The Journal of biological chemistry》1971,246(23):7383-7391
57.
Snake venom toxins. The amino acid sequences of toxins b and d from Naja melanoleuca venom 总被引:1,自引:0,他引:1
D P Botes 《The Journal of biological chemistry》1972,247(9):2866-2871
58.
59.
M. P. Roux J. L. F. Kock A. Botha J. C. du Preez G. V. Wells P. J. Botes 《World journal of microbiology & biotechnology》1994,10(4):417-422
Lipid analyses were performed on 28 strains of various species of the genus Mucor. In shake flasks with glucose as carbon source, the gamma-linolenic acid (GLA) content in the neutral lipid (NL) fraction of some Mucor species was up to 38 mg GLA/g dry biomass. Some Mucor species produced more than 20% (w/w) stearic acid (18:0) and more than 60% of their NL content as symmetrical triacylglycerols (SUS-TAGs) which corresponded to those of cocoa butter. Three Mucor species were evaluated in terms of the production of SUS-TAGs and GLA in pH-stat, fed-batch cultures in an air-lift fermenter with acetic acid as titrant and carbon source. Mucor circinelloides f. circinelloides CBS 108.16 accumulated 27% 18:0 in the NL fraction, which constituted approximately 40% of the dry biomass. In this case, the NL fraction contained more than 70% (w/w) SUS-TAGs.M.P. Roux, J.L.F. Kock, A. Botha, J.C. du Preez and P.J. Botes are with the Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein 9300, South Africa; G.V. Wells is with Sasol Waxes, P.O. Box 1, Sasolburg, South Africa. 相似文献
60.
Leeuw NJ Swart CW Ncango DM Pohl CH Sebolai OM Strauss CJ Botes PJ van Wyk PW Nigam S Kock JL 《Antonie van Leeuwenhoek》2007,91(4):393-405
Interesting distribution patterns of acetylsalicylic acid (ASA, aspirin) sensitive 3-hydroxy (OH) oxylipins were previously
reported in some representatives of the yeast genus Eremothecium—an important group of plant pathogens. Using immunofluorescence microscopy and 3-OH oxylipin specific antibodies in this
study, we were able to map the presence of these compounds also in other Eremothecium species. In Eremothecium cymbalariae, these oxylipins were found to cover mostly the spiky tips of narrowly triangular ascospores while in Eremothecium gossypii, oxylipins covered the whole spindle-shaped ascospore with terminal appendages. The presence of these oxylipins was confirmed
by chemical analysis. When ASA, a 3-OH oxylipin inhibitor, was added to these yeasts in increasing concentrations, the sexual
stage was found to be the most sensitive. Our results suggest that 3-OH oxylipins, produced by mitochondria through incomplete
β-oxidation, are associated with the development of the sexual stages in both yeasts. Strikingly, preliminary studies on yeast
growth suggest that yeasts, characterized by mainly an aerobic respiration rather than a fermentative pathway, are more sensitive
to ASA than yeasts characterized by both pathways. These data further support the role of mitochondria in sexual as well as
asexual reproduction of yeasts and its role to serve as a target for ASA antifungal action. 相似文献