Biomedical subjects
Publications and source records attributed to J C de Bruyn.
The results of a confidential inquiry into mortality attributed to malaria in South Africa's Mpumalanga Province are being used to guide the design of strategies for improving the management of cases and reducing the probability of deaths from the disease.
The obligately autotrophic acidophile Thiobacillus ferrooxidans was grown on elemental sulfur in anaerobic batch cultures, using ferric iron as an electron acceptor. During anaerobic growth, ferric iron present in the growth media was quantitatively reduced to ferrous iron. The doubling time in anaerobic cultures was approximately 24 h. Anaerobic growth did not occur in the absence of elemental sulfur or ferric iron. During growth, a linear relationship existed between the concentration of ferrous iron accumulated in the cultures and the cell density. The results suggest that ferric iron may be an important electron acceptor for the oxidation of sulfur compounds in acidic environments.
Nuclepore polycarbonate filters floating on a liquid, FeSO(4)-containing medium (pH 1.6) were used to isolate a moderately thermophilic bacterium from a pyrite-oxidizing enrichment culture. The isolate failed to grow on any of the conventional solid media tried. To test the general applicability of the method, the enumeration of a fastidious acidophilic organism, Thiobacillus ferrooxidans, was carried out and the results compared with those obtained with other filters, solid media, and the most probable number technique. T. ferrooxidans showed better viability on the floating polycarbonate filters and grew in a much shorter time (4 to 5 days) than with the other techniques.
The relationship between the rates of methane and ethane oxidation by washed suspensions of methane-oxidizing bacteria has been investigated. Considerable differences between bacterial strains were observed. Two closely related Methylomonas strains which differed in their oxidizing capacity were further investigated. The low ethane oxidation rate of one strain could be strongly stimulated by the addition of oxidizable co-substrates and the presence of ethane stimulated formate oxidation. The other strain had a much higher ethane oxidation rate and stimulation by co-substrates was negligible. Differences between the levels of dissimilative enzymes in cell-free extracts could not be detected. Attempts to produce extracts with methane mono-oxygenase activity failed. When cells were made permeable with chitosan the results suggested that strains with a low ethane oxidizing capacity obtain the required reductant for the moo-oxygenase from endogenous respiration. In strains with a high ethane oxidation rate, the reductant appears to be derived from oxidation of ethanol or acetaldehyde.
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