- Volume 5, Issue 2, 1951
Volume 5, Issue 2, 1951
- Article
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The Adsorption of Cetyltrimethylammonium Bromide by Bacteria, its Action in Releasing Cellular Constituents and its Bactericidal Effects
More LessSUMMARY: The form of the uptake curve of cetyltrimethylammonium bromide (CTAB) by Staphylococcus aureus and Escherichia coli is that of an adsorption isotherm. Tested on six different bacteria, the maximum amounts of CTAB adsorbed showed variations from one organism to another.
When ceils of Staphylococcus aureus. Streptococcus faecalis, Escherichia coli or Salmonella pullorum are suspended in water, the ultra-violet spectrum of the supernatant liquid has a maximum absorption at a wave-length of 260 mμ. The height of this maximum is greatly increased when the cells are suspended in CTAB solutions instead of water. Free purines and pyrimidines contribute to this maximum.
There is a parallel relationship between the leakage of 260 mμ.-absorbing material, glutamic acid and inorganic phosphorus from two CTAB-treated Gram-positive bacteria, when their release is followed during the initial rapid phase of leakage. There is a similar relationship for Each. coli. although no glutamic acid is released. Release of cell constituents from CTAB-treated Staph. aureus continues slowly for some time after the initial process and is accompanied by a decrease in dry weight of the cells and a gradual change from positive to negative in their Gram-staining reaction. The rate of release of cellular constituents was increased by raising the temperature or by treatment with high concentrations of CTAB.
Treatment of suspensions with sufficient CTAB to sterilize them released amounts of cell constituents comparable to those released by placing the cells in boiling water. When smaller amounts of CTAB were used, a quantitative relationship was found between the amount of CTAB present, the proportion of cells killed and the amount of 260 mμ.-absorbing material released.
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Electron Microscopy of Bacteria treated with Cetyltrimethylammonium Bromide
More LessSUMMARY: When viewed in the electron microscope, cells of Staphylococcus aureus, Streptococcus faecalis and Escherichia coli changed markedly when suspended in cetyltrimethylammonium bromide (CTAB) solutions instead of distilled water; the cytoplasm contracts away from the cell wall. The proportion of cells showing such contraction, in the case of Esch. coli, can he correlated with the proportion of cells killed by the treatment. High concentrations of CTAB appear to strip off the cell envelopes.
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Observations on the Value of the Bordet-Gengou Medium for the Cultivation of Haemophilus pertussis
More LessSUMMARY: No significant improvement has been made on the medium first described for the primary culture of Haemophilus pertussis by Bordet & Gengou in 1906. An explanation for this was sought in the experiments described, and it was found to be most probable that potato extract provides optimal concentrations of amino-acids and peptides required for growth. Although serum can be used to replace whole blood in this medium, the latter is essential for maximal growth; for that reason the retention of the term haemophilus is justified.
Many peptones, especially the more digested ones, inhibit growth of H. pertussis in concentrations normally used in bacteriological media. In the absence of peptone, meat extract agar can be used as the base of a satisfactory medium, especially when used in conjunction with horse instead of rabbit blood.
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The Assay of Vitamin B12: I. Factors affecting the Response of Lactobacillus lactis Dorner ATCC 8000 to Vitamin B12
More LessSUMMARY: For maximal zones of ‘exhibition’ in the plate test for vitamin B12 with Lactobacillus laclis Dorner ATCC 8000, using the media described, the presence of both oxygen and vitamin B12 is necessary. Under anaerobic conditions the vitamin is not an essential growth factor and under highly aerobic conditions growth does not occur even in its presence. Under the conditions of maintenance used variant strains were not detected.
When grown in the presence of vitamin B12 the bacteria may store sufficient of the vitamin to render measurements of growth useless for assay purposes: when grown under anaerobic conditions the culture obtained is unsuitable for use as an inoculum. A technique for preparing satisfactory inocula of the test organisms and the conditions necessary for well-defined responses to vitamin B12 are described.
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- Corrigendum
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