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At least 595 records · Page 33Linked to original sources
PubMed1961

Effects of deoxyribonucleic acid products on deoxyribonucleic acid synthesis of virulent and avirulent pneumococci.

Firshein, W. (Wesleyan University, Middletown, Conn.). Effects of deoxyribonucleic acid products on deoxyribonucleic acid synthesis of virulent and avirulent pneumococci. J. Bacteriol. 82:169-180. 1961.-Cell suspensions of virulent pneumococci synthesize a greater amount of deoxyribonucleic acid (DNA) per cell in the presence of DNA + deoxyribonuclease + mixtures of deoxynucleosides and deoxynucleotides (supplement-1) than unsupplemented suspensions. Under identical conditions, avirulent and weakly virulent pneumococci do not respond to these DNA breakdown products. Glucose and casitone must be present for maximal effects to occur.A DNA turnover occurs in virulent cells. This has been demonstrated by a decrease in specific activity of H(3)-DNA extracted from virulent (S) cells exposed to nonradioactive supplement-1.

DNA↗
PubMed1961

Effects of deoxyribonucleic acid products on respiration of virulent and avirulent pneumococci.

Firshein, W. (Wesleyan University, Middletown, Conn.). Effects of deoxyribonucleic acid products on respiration of virulent and avirulent pneumococci. J. Bacteriol. 82:181-186. 1961.-In the presence of deoxyribonucleic acid (DNA) + deoxyribonuclease + mixtures of deoxynucleosides and deoxynucleotides (supplement-1) which had previously been shown to enhance DNA synthesis in virulent (S) pneumococci without affecting such synthesis in avirulent (R) pneumococci, a significant enhancement of glucose oxidation was observed over control levels in S cells of types I, II, and III. In contrast, this supplement either depressed oxygen uptake or had no effect when R or weakly virulent (I) pneumococci were present. In the absence of glucose, S cells were unable to oxidize supplement-1 extensively, whereas R cells exhibited definite activity in this respect. Supplement-1 enhanced glucose oxidation specifically and was not oxidized in the process. The selective advantage produced by the DNA products in S cells could not be explained on the basis of nitrogen content, since a substance containing twice as much of this element as that found in the entire supplement did not enhance oxygen uptake to the extent that was observed with supplement-1.

Cell Respiration↗
PubMed1961

Genetic modifiers of streptomycin resistance in Pneumococcus.

Bryan, Betty E. (University of Rochester, Rochester, N. Y.). Genetic modifiers of streptomycin resistance in pneumococcus. J. Bacteriol. 82:461-470. 1961.-Streptomycin-resistant mutants arising spontaneously in pneumococcus vary widely with respect to the maximal concentrations of streptomycin which they resist. A small random sample of these mutations tested for linkage are allelic or closely linked. One single-step mutant resisting a relatively low level of streptomycin undergoes the following changes: (i) replacement (by a secondary mutation) of the original mutation by an allele conferring a high level of resistance; (ii) reversion to complete sensitivity by back mutation at the originally mutated site; (iii) enhancement by an unlinked modifier gene which confers no resistance by itself but raises the level of resistance of the mutant strain approximately 10-fold. This modifier may have some specificity in its action on the different mutations occurring at a gene locus.The possibility is discussed that multi-step resistance may often originate by acquisition of modifiers.

Drug Resistance, Microbial↗
PubMed1961

Immunochemistry of pneumococcal types II, V, and VI. II. Inhibition tests in the type VI precipitating system.

Rebers, Paul A. (Rutgers University, New Brunswick, N. J.), Esther Hurwitz, and Michael Heidelberger. Immunochemistry of pneumococcal types II, V, and VI. II. Inhibition tests in the type VI precipitating system. J. Bacteriol. 82:920-926. 1961.-As in other immune systems involving polysaccharides, rabbit antibodies but not those engendered in the horse were found sensitive to degradation of type VI pneumococcal (Pn) polysaccharide (SVI), and were readily inhibited by fragments of SVI. Large amounts, 30 to 111 mumoles, of most sugars gave up to 15% inhibition, while sugar and polyol phosphates inhibited as much as 25%, with little relation to their presence or absence in SVI. The phosphate-free repeating unit of SVI was a good inhibitor, its phosphate monoester was better, and the "trimer" still better. The "trimer" precipitated most of the antibodies from horse anti-Pn VI.Although inhibition of precipitation of SVI anti-Pn horse sera could not be demonstrated with fragments of SVI, cross-reactions of antibodies in the horse sera could be inhibited. Precipitation of SII was inhibited by low concentrations of l-rhamnose, while even high concentrations of the other sugar components of SII and SVI were ineffective. Precipitation by guar gum was inhibited by galactose and alpha- and beta-methyl-galactopyranosides, also by rhamnose, although guar gum does not contain this sugar, while SVI, the antigenic determinant, does.

Animals↗
PubMed1962

Immunochemistry of the pneumococcal types II, V, and VI. III. Tests with derivatives of the specific polysaccharides of types II and VI.

Rebers, P. A. (Rutgers, The State University, New Brunswick, N. J.), E. Hurwitz, M. Heidelberger, and S. Estrada-Parra. Immunochemistry of the pneumococcal types II, V, and VI. III. Tests with derivatives of the specific polysaccharides of types II and VI. J. Bacteriol. 83:335-342. 1962.-The type-specific pneumococcal polysaccharides, S II and S VI, were oxidized with periodate, and the capacity of the derivatives for precipitation by antibodies and adsorption by erythrocytes was studied. The derivatives were further modified by reduction, oxidation, and condensation with urea. Oxidation of S VI with periodate reduced its precipitation of homologous antibodies much less than did similar treatment of S II. About one-half of the components are attacked in both cases, but in S II, glucuronic acid end groups, the chief determinants of specificity, are destroyed by periodate, whereas in S VI, the structures responsible for specificity are either less affected or yield derivatives with almost as much affinity for antibody as the original polysaccharide. S II and S VI are not adsorbed by washed rabbit or human erythrocytes, but their periodate-oxidized derivatives are readily taken up, presumably owing to their newly formed reactive aldehyde groups, giving high titers in passive hemagglutination. The method should be applicable to other polysaccharides which do not adsorb readily on red cells.

Animals↗
PubMed1962

Effect of manganese and enzymatic deoxyribonucleic acid digests on population changes and respiration of Pneumococci.

Firshein, William (Wesleyan University, Middletown, Conn.). Effect of manganese and enzymatic deoxyribonucleic acid digests on population changes and respiration of pneumococci. J. Bacteriol. 84:478-484. 1962.-Deoxyribonucleic acid (DNA; Na salt) treated with deoxyribonuclease and Mn(++) (as MnSO(4)) stimulated R (avirulent) to S (virulent) population changes in vitro. Under certain environmental conditions and with certain strains, Mn(++) alone elicited these changes, but, in most cases, both digested DNA and Mn(++) were necessary for maximal effect. These population changes were due to a selective stimulation of the multiplication of S cells and a delay in S-cell lysis, with either a slight inhibitory effect or no effect against the multiplication of R cells. The magnitude of the population change depended upon the presence of digested DNA, the level of Mn(++), the strain, and the concentration of basal medium. Mn(++) enhanced respiration of S cells while inhibiting that of R cells.

DNA↗
PubMed1963

BACTERIAL NUCLEOTIDASES.

Kohn, J. (Queen Mary's Hospital, London, England) and J. L. Reis. Bacterial nucleotidases. J. Bacteriol. 86:713-716. 1963.-The 3- and 5- nucleotidase activity in various bacterial species was investigated. Both enzymes were found in bacterial extracts in varying proportions. The nucleotidases were found to be very active in Proteus vulgaris, in which organism they were studied in detail. The relative activities, the pH optima, and the effect of metal ions were investigated. It was concluded that bacterial 3- and 5-nucleotidases are distinct and separate enzymes.

Bacillus cereus↗
PubMed1964

GENETIC LINKAGE OF MUTATIONAL SITES AFFECTING SIMILAR CHARACTERS IN PNEUMOCOCCUS AND STREPTOCOCCUS.

Ravin, Arnold W. (University of Rochester, Rochester, N.Y.), and Joscelyn D. H. De Sa. Genetic linkage of mutational sites affecting similar characters in pneumococcus and streptococcus. J. Bacteriol. 87:86-96. 1964.-By interspecific transformation, deoxyribonucleic acid (DNA) determinants conferring resistance to high levels of streptomycin in pneumococcus were found to be allelic with DNA determinants conferring low levels of streptomycin resistance in the Challis and NBSI strains of streptococcus. The reciprocal transformation (low resistance pneumococcus x high resistance streptococcus) led to the same conclusion. In addition, determinants controlling resistance to erythromycin in pneumococcus and the Challis strain of streptococcus were found to become closely linked after interspecific transformation. Modifier genes influencing the phenotype conferred by mutations at the streptomycin-resistance locus differentiate species to a certain extent. The results demonstrate that transformations between pneumococcus and streptococcus are not due to episomes, but involve recombinational events in which genetic material of the host species is replaced by homologous material that performed a similar function in the donor species.

DNA↗