- Volume 42, Issue 1, 1966
Volume 42, Issue 1, 1966
- Article
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Micro-Electrophoresis of Cowpox and Vaccinia Viruses in Molar Sucrose
More LessSUMMARY: Preparations of cowpox and vaccinia viruses, grown on rabbit skin and on chick chorioallantois, purified by methods involving Arcton treatment or centrifugation in sucrose density gradients gave electrophoretically reproducible materials. A micro-electrophoresis technique is described with which measurements may be made conveniently and reproducibly on individual virus particles suspended in buffered molar sucrose solutions. The viruses had a mobility of approximately —0.4 μ/sec./V./cm. in molar sucrose at pH 7 and ionic strength 0.05, their negative charge decreasing with decreasing pH value to give isoelectric points at pH 4.3 for cowpox, 3.7 for egg-grown vaccinia and 3.0 for rabbit-grown vaccinia; in greater acidities the viruses were positively charged. The results showed close reproducibility for the final preparations of cowpox of different origin and treatment, suggesting that the virus suspensions were relatively pure and free from adsorbed or extraneous material. Similar reproducibility was found for rabbit-grown vaccinia virus preparations, but there was some variation among different preparations of egg-grown vaccinia virus.
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Micro-Electrophoresis of Cowpox and Vaccinia Viruses in Molar Sucrose
More LessSUMMARY: Preparations of cowpox and vaccinia viruses, grown on rabbit skin and on chick chorioallantois, purified by methods involving Arcton treatment or centrifugation in sucrose density gradients gave electrophoretically reproducible materials. A micro-electrophoresis technique is described with which measurements may be made conveniently and reproducibly on individual virus particles suspended in buffered molar sucrose solutions. The viruses had a mobility of approximately —0.4 μ/sec./V./cm. in molar sucrose at pH 7 and ionic strength 0.05, their negative charge decreasing with decreasing pH value to give isoelectric points at pH 4.3 for cowpox, 3.7 for egg-grown vaccinia and 3.0 for rabbit-grown vaccinia; in greater acidities the viruses were positively charged. The results showed close reproducibility for the final preparations of cowpox of different origin and treatment, suggesting that the virus suspensions were relatively pure and free from adsorbed or extraneous material. Similar reproducibility was found for rabbit-grown vaccinia virus preparations, but there was some variation among different preparations of egg-grown vaccinia virus.
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Cell-Wall Deficiencies in L-forms of Staphylococcus aureus
More LessSUMMARY: Three strains of penicillin-induced and one strain of D-cycloserine-induced L-forms of Staphylococcus aureus were investigated for components of the normal bacterial cell wall. None of the 4 strains was found to contain more than 0.008% of its dry weight as muramic acid, indicating the lack of mucopeptide. These forms also lacked the cell-wall ribitol teichoic acid as shown by the failure to yield any material containing ribitol. Neither muramic acid nor ribitol was detected as acid-soluble nucleotides in the L-forms, and teichoic acid was not released into the supernatant medium. Serological evidence for polysaccharide A was not found, but there was serological identity between extracts of membranes obtained from staphylococci and extracts of membranes isolated from the L-forms.
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Cell-Wall Deficiencies in L-forms of Staphylococcus aureus
More LessSUMMARY: Three strains of penicillin-induced and one strain of D-cycloserine-induced L-forms of Staphylococcus aureus were investigated for components of the normal bacterial cell wall. None of the 4 strains was found to contain more than 0.008% of its dry weight as muramic acid, indicating the lack of mucopeptide. These forms also lacked the cell-wall ribitol teichoic acid as shown by the failure to yield any material containing ribitol. Neither muramic acid nor ribitol was detected as acid-soluble nucleotides in the L-forms, and teichoic acid was not released into the supernatant medium. Serological evidence for polysaccharide A was not found, but there was serological identity between extracts of membranes obtained from staphylococci and extracts of membranes isolated from the L-forms.
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On the Nature of Mixed Cultures of Chlorella Pyrenoidosa TX 71105 and Various Bacteria
More LessSUMMARY: The growth of several selected micro-organisms in rapidly dividing cultures of Chlorella pyrenoidosa TX 71105 was studied. Bacterial proliferation was a function of algal growth and bacterial growth occurred, at least in part, as a result of the excretion of organic substances into the culture medium by rapidly dividing algae. These substances capable of supporting bacterial oxidation and growth were varied in kind and were utilized selectively by the different bacteria. Only a small fraction of the soil and air bacteria grew in the algal cultures. The majority of soil and air bacteria survived in mixed culture for several days but did not increase in numbers. On the other hand, 6 out of 8 bacteria pathogenic for man died promptly in cultures of Chlorella pyrenoidosa; but Salmonella typhi and S. paratyphi grew well for extended periods of time. Fungi capable of producing macrocolonies on potato glucose agar at pH 3.5 did not increase in numbers during 8 days. Yeasts and actinomycetes were not detected by the methods used; bacteriophages were observed with some regularity.
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On the Nature of Mixed Cultures of Chlorella Pyrenoidosa TX 71105 and Various Bacteria
More LessSUMMARY: The growth of several selected micro-organisms in rapidly dividing cultures of Chlorella pyrenoidosa TX 71105 was studied. Bacterial proliferation was a function of algal growth and bacterial growth occurred, at least in part, as a result of the excretion of organic substances into the culture medium by rapidly dividing algae. These substances capable of supporting bacterial oxidation and growth were varied in kind and were utilized selectively by the different bacteria. Only a small fraction of the soil and air bacteria grew in the algal cultures. The majority of soil and air bacteria survived in mixed culture for several days but did not increase in numbers. On the other hand, 6 out of 8 bacteria pathogenic for man died promptly in cultures of Chlorella pyrenoidosa; but Salmonella typhi and S. paratyphi grew well for extended periods of time. Fungi capable of producing macrocolonies on potato glucose agar at pH 3.5 did not increase in numbers during 8 days. Yeasts and actinomycetes were not detected by the methods used; bacteriophages were observed with some regularity.
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The Role of Cellular Lipid in the Resistance of Gram-positive Bacteria to Penicillins
More LessSUMMARY: It has been shown that when the Gram-positive micro-organisms Bacillus subtilis, Staphylococcus aureus and Streptococcus faecalis were grown under conditions in which their cellular lipid was increased a corresponding increase in their resistance to the penicillins benzylpenicillin, cloxacillin, methicillin and quinacillin was produced. Likewise cell-wall lipid depletion caused a corresponding increase in sensitivity.
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The Role of Cellular Lipid in the Resistance of Gram-positive Bacteria to Penicillins
More LessSUMMARY: It has been shown that when the Gram-positive micro-organisms Bacillus subtilis, Staphylococcus aureus and Streptococcus faecalis were grown under conditions in which their cellular lipid was increased a corresponding increase in their resistance to the penicillins benzylpenicillin, cloxacillin, methicillin and quinacillin was produced. Likewise cell-wall lipid depletion caused a corresponding increase in sensitivity.
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Variations in Mycoplasma Morphology Induced by Long-chain Fatty Acids
More LessSUMMARY: Addition of unsaturated long-chain fatty acids to tryptose broth improved growth of Mycoplasma laidlawii and induced the formation of very long and highly branched filaments by this organism. Most filaments were composed of small coccoid bodies. The saturated long-chain fatty acids, in a similar concentration, did not produce this effect; palmitic and stearic acids inhibited growth. Similar, but less striking results were obtained with M. gallisepticum and Mycoplasma sp. strain 14. The possibility that the morphological variations reflect changes in the lipid composition of the cell membrane is discussed.
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Variations in Mycoplasma Morphology Induced by Long-chain Fatty Acids
More LessSUMMARY: Addition of unsaturated long-chain fatty acids to tryptose broth improved growth of Mycoplasma laidlawii and induced the formation of very long and highly branched filaments by this organism. Most filaments were composed of small coccoid bodies. The saturated long-chain fatty acids, in a similar concentration, did not produce this effect; palmitic and stearic acids inhibited growth. Similar, but less striking results were obtained with M. gallisepticum and Mycoplasma sp. strain 14. The possibility that the morphological variations reflect changes in the lipid composition of the cell membrane is discussed.
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The Chemical Composition of the Cell Walls of Some Thermophilic Bacilli
More LessSUMMARY: The chemical compositions of the cell walls of one strain each of Bacillus stearothermophilus and B. coagulans prepared from organisms grown at 37° and 55° are compared. The higher temperature of cultivation resulted in an increased proportion of mucopeptide and a decreased proportion of teichoic acid in the walls of both organisms. A higher lipid content than is usual in Gram-positive organisms was found in these walls. The teichoic acid from B. stearothermophilus walls was a glycerophosphate polymer substituted with glucose and alanine; evidence suggesting the presence of 2,3-phosphodiester linkages in this polymer is presented. The teichoic acid from B. coagulans walls was also a glycerophosphate polymer, substituted with two neutral sugars, glucose and galactose, but lacking amino acid substituents hitherto reported as characteristic of teichoic acids.
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The Chemical Composition of the Cell Walls of Some Thermophilic Bacilli
More LessSUMMARY: The chemical compositions of the cell walls of one strain each of Bacillus stearothermophilus and B. coagulans prepared from organisms grown at 37° and 55° are compared. The higher temperature of cultivation resulted in an increased proportion of mucopeptide and a decreased proportion of teichoic acid in the walls of both organisms. A higher lipid content than is usual in Gram-positive organisms was found in these walls. The teichoic acid from B. stearothermophilus walls was a glycerophosphate polymer substituted with glucose and alanine; evidence suggesting the presence of 2,3-phosphodiester linkages in this polymer is presented. The teichoic acid from B. coagulans walls was also a glycerophosphate polymer, substituted with two neutral sugars, glucose and galactose, but lacking amino acid substituents hitherto reported as characteristic of teichoic acids.
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The Regulation of Cystathionine Formation in Escherichia coli
More LessSUMMARY: The amounts of cystathionine-forming enzymes (homoserine O-trans-succinylase and cystathionine synthetase) of Escherichia coli were decreased by growth with methionine, and therefore enzymic repression applied to all the enzymes of the methionine biosynthetic pathway. Enzyme resynthesis occurred when ‘inactive’ organisms (organisms grown with methionine) were suspended in methionine-free culture fluid. Although the formation of all the enzymes of the pathway appears to be controlled by a single regulator gene, co-ordinate repression and de-repression were not observed. Methionine also regulates its own synthesis by inhibition of the activity of homoserine O-trans-succinylase, the inhibitory effect being more marked with intact organisms than with cell-free extracts. Methionine did not influence the activity of cystathionine synthetase or the subsequent methionine-forming enzymes.
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The Regulation of Cystathionine Formation in Escherichia coli
More LessSUMMARY: The amounts of cystathionine-forming enzymes (homoserine O-trans-succinylase and cystathionine synthetase) of Escherichia coli were decreased by growth with methionine, and therefore enzymic repression applied to all the enzymes of the methionine biosynthetic pathway. Enzyme resynthesis occurred when ‘inactive’ organisms (organisms grown with methionine) were suspended in methionine-free culture fluid. Although the formation of all the enzymes of the pathway appears to be controlled by a single regulator gene, co-ordinate repression and de-repression were not observed. Methionine also regulates its own synthesis by inhibition of the activity of homoserine O-trans-succinylase, the inhibitory effect being more marked with intact organisms than with cell-free extracts. Methionine did not influence the activity of cystathionine synthetase or the subsequent methionine-forming enzymes.
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