Showing papers in "Journal of Bacteriology in 1968"
TL;DR: Myeloperoxidase, at high concentrations, exerted an antibacterial effect on L. acidophilus in the absence of added halide, which also was temperature- and catalase-sensitive, and suggests that, under the conditions employed, the antibacterial properties of a weak acid extract of guinea pig leukocytes is due, in part, to its peroxid enzyme content, particularly if a halide is present in the reaction mixture.
Abstract: An antibacterial effect of myeloperoxidase, a halide, such as iodide, bromide, or chloride ion, and H2O2 on Escherichia coli or Lactobacillus acidophilus is described. When L. acidophilus was employed, the addition of H2O2 was not required; however, the protective effect of catalase suggested that, in this instance, H2O2 was generated by the organisms. The antibacterial effect was largely prevented by preheating the myeloperoxidase at 80 C or greater for 10 min or by the addition of a number of inhibitors; it was most active at the most acid pH employed (5.0). Lactoperoxidase was considerably less effective than was myeloperoxidase when chloride was the halide employed. Myeloperoxidase, at high concentrations, exerted an antibacterial effect on L. acidophilus in the absence of added halide, which also was temperature- and catalase-sensitive. Peroxidase was extracted from intact guinea pig leukocytes by weak acid, and the extract with peroxidase activity had antibacterial properties which were similar, in many respects, to those of the purified preparation of myeloperoxidase. Under appropriate conditions, the antibacterial effect was increased by halides and by H2O2 and was decreased by catalase, as well as by cyanide, azide, Tapazole, and thiosulfate. This suggests that, under the conditions employed, the antibacterial properties of a weak acid extract of guinea pig leukocytes is due, in part, to its peroxidase content, particularly if a halide is present in the reaction mixture. A heat-stable antibacterial agent or agents also appear to be present in the extract.
819 citations
TL;DR: The amino acid phenylalanine is shown to become incorporated intact into lipidic compounds which have been partially characterized and have been examined for their utility with these bacteria.
Abstract: The nature and quantity of the phospholipids of Salmonella typhimurium and Escherichia coli K-12 have been examined. The main classes of phospholipids, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin have been completely characterized. Four minor compounds have been detected: phosphatidylserine, phosphatidic acid, and two partially characterized lipids. The phospholipid composition of the two organisms is quite similar, the only difference is the absence of one of the minor components and a decreased level of all components in E. coli. A study of the turnover of the phosphate in the phospholipids demonstrated no turnover in phosphatidylethanolamine, a slow turnover in phosphatidylglycerol, and a slow turnover in cardiolipin with, possibly, a transfer of phosphate from phosphatidylglycerol to cardiolipin. The amino acid phenylalanine is shown to become incorporated intact into lipidic compounds which have been partially characterized. Methods for the isolation and separation of lipids have been examined for their utility with these bacteria.
604 citations
TL;DR: The term prostheca is proposed for the rigid appendages of procaryotic cells bounded by the cell wall, and is defined to include the structures on these new bacteria, as well as the stalks of the caulobacters and thehyphae of the hyphomicrobia.
Abstract: Direct microscopic examination of natural freshwater samples reveals a variety of small microorganisms having elaborate cellular appendages. Several strains have been isolated from crude cultures containing low concentrations of organic nutrients. All of the isolates are procaryotic. They are aerobic chemoorganotrophs that require vitamins for growth. Because they cannot be assigned to any of the existing bacterial genera, two new genera are proposed: Ancalomicrobium for organisms which have several long appendages and which reproduce by budding; Prosthecomicrobium for organisms which have many short appendages tapering toward a blunt tip and which reproduce by binary fission. Gas vacuoles have been found in strains of each genus. The term prostheca is proposed for the rigid appendages of procaryotic cells bounded by the cell wall, and is defined to include the structures on these new bacteria, as well as the stalks of the caulobacters and the hyphae of the hyphomicrobia.
551 citations
TL;DR: Neither the hydrolysis of gelatin nor acid production from aldose sugars was found to be a reliable index of strain affinities indicated by the phenotypic analysis, although both properties were of some use in distinguishing between the subgroups.
Abstract: A number of nutritional and biochemical properties of more than 100 strains of the oxidase-negative moraxellas (the Mima-Herellea-Acinetobacter group of bacteria) were studied. These properties included the range of carbon sources that can support growth, the utilization of nitrate, the production of proteolytic and lipolytic enzymes, and the reactions involved in the oxidation of sugars and of aromatic compounds. No evidence could be obtained for the accumulation of either poly-beta-hydroxybutyrate or polysaccharide as intracellular reserve materials. Of 158 different compounds tested, the group as a whole could use 85 as sole carbon sources for growth. The nutritional spectra of the individual strains, however, differed widely, with a range of from 17 to 74 alternative substrates. On the basis of 56 selected nutritional and physiological characters used for a numerical analysis, the collection could be divided into two major groups of strains comprising at least seven less clearly defined clusters. Neither the hydrolysis of gelatin nor acid production from aldose sugars was found to be a reliable index of strain affinities indicated by the phenotypic analysis, although both properties were of some use in distinguishing between the subgroups. For reasons that are discussed, we propose that the oxidase-negative moraxellas be placed in the genus Acinetobacter Brisou and Prevot, for which a modified description is presented. A. calco-aceticus (Beijerinck) is proposed as the type species, of which anitratum is regarded as a synonym or variety. On the basis of the present studies and unpublished supporting evidence provided by M. Mandel on deoxyribonucleic acid (DNA) composition and by J. Johnson on DNA homologies, it is proposed that two other species in the genus, A. lwoffi (Audureau) and A. hemolysans (Henriksen), as well as one subspecies, A. hemolysans haemolyticus (Stenzel and Mannheim), be recognized provisionally.
428 citations
TL;DR: During 35 months of selective in vitro cultivation, Neisseria gonorrhoeae cells retained their virulence for humans and were shown to be closely related to a particular colonial morphology.
Abstract: During 35 months of selective in vitro cultivation, Neisseria gonorrhoeae cells retained their virulence for humans and were shown to be closely related to a particular colonial morphology. Saline-autoagglutinability was the only other characteristic distinguishing virulent from avirulent cells. Human responses to challenge with cells of the different colonial types were studied for their relationships to virulence or avirulence.
425 citations
TL;DR: The penicillinase plasmids, aseries of extrachromosomal resistance factors in Staphylococcus aureus, were found to carry determinants of resistance to a series of inorganic ions as well as resistance topenicillin and, in some cases, erythromycin, causing an increase in resistance by comparison with susceptible organisms of between 3- and 100-fold.
Abstract: The penicillinase plasmids, a series of extrachromosomal resistance factors in Staphylococcus aureus, were found to carry determinants of resistance to a series of inorganic ions as well as resistance to penicillin and, in some cases, erythromycin. Most of the ions involved were inhibitory but not lethal to the bacteria; the resistance markers conferred an increase in resistance by comparison with susceptible organisms of between 3- and 100-fold, depending on the ion involved. Separate genetic loci for resistance to arsenate, arsenite, lead, cadmium, mercuric, and bismuth ions were demonstrated. Resistance to antimony and resistance to zinc were also found but were not separated genetically from resistance to arsenite and cadmium, respectively. The ion resistance markers appeared to form a cluster on the plasmid, with no other known marker within it. Naturally occurring plasmids were observed that lacked one or more of these ion resistance markers, as well as penicillinase-negative strains that were resistant to one or more of the ions. The patterns of markers carried by these various strains may provide some understanding of the evolution of a plasmid linkage group.
412 citations
TL;DR: Comparisons of the numbers of Acinetobacter and of all bacteria capable of aerobic growth in a complex medium revealed that AcinetOBacter constituted no less than 0.001% of the total heterotrophic aerobic population in soil and water and was one of the predominant organisms in some water samples.
Abstract: An enrichment culture procedure for isolating members of the genus Acinetobacter from soil and water is described. It involves the use of vigorously aerated mineral media at relative low pH, supplemented with acetate or other suitable carbon source and nitrate as nitrogen source. With this method, virtually all samples of soil and water yielded representatives of this genus. Semiquantitative comparisons of the numbers of Acinetobacter and of all bacteria capable of aerobic growth in a complex medium revealed that Acinetobacter constituted no less than 0.001% of the total heterotrophic aerobic population in soil and water and was one of the predominant organisms in some water samples.
292 citations
TL;DR: A method has been devised for the rapid identification of nonsense mutations (UAG, UAA, UGA codons) in Salmonella by replica-printed onto lactose plates spread with lawns of tester strains containing nonsense mutations in the episomal Z gene.
Abstract: A method has been devised for the rapid identification of nonsense mutations (UAG, UAA, UGA codons) in Salmonella. The mutations to be tested are reverted, and the revertants are replica-printed onto lactose plates spread with lawns of tester strains. These tester strains contain F' lac episomes with nonsense mutations in the episomal Z gene. The revertants are infected with the episome from the tester strain lawn. Because S. typhimurium is unable to ferment lactose, only those revertants which have nonsense suppressors are able to grow on lactose. If colonies appear on the lactose plate, it may be concluded that the original strain carries a nonsense mutation, since nonsense suppressors suppress the mutant phenotype.
287 citations
TL;DR: Mutants that have simultaneously lost feedback inhibition by uridine triphosphate for carbamoyl phosphate synthetase and for aspartic transcarbamylase have been found and mapped in the gene ura-2.
Abstract: Biochemical steps of the pyrimidine pathway have been found to be the same in yeast as in bacteria, and all except one step have been characterized. The activities of the first two enzymes, carbamoyl phosphate synthetase and aspartic transcarbamylase, are simultaneously controlled by feedback inhibition and repression. Moreover, these enzymes are coded by the same genetic region (ura-2) and seem to form a single enzymatic complex. The enzymes that follow later in the pathway are induced in a sequential way by the intermediary products and are insensitive to pyrimidine repression. The corresponding genes (ura-4, ura-1, ura-3) are not linked to each other or to ura-2, the gene for carbamoyl phosphate synthetase and aspartic transcarbamylase. Mutants that have simultaneously lost feedback inhibition by uridine triphosphate for carbamoyl phosphate synthetase and for aspartic transcarbamylase have been found and mapped in the gene ura-2.
280 citations
TL;DR: Determinations of the salt sensitivity of enzymes extracted from the halophilic alga Dunaliella viridis revealed that pentose phosphate isomersase, ribulose diphosphate carboxylase, glucose-6-phosphate dehydrogenase, and phosphohexose isomerase were inhibited by NaCl concentrations far lower than that in the growth medium.
Abstract: Determinations of the salt sensitivity of enzymes extracted from the halophilic alga Dunaliella viridis revealed that pentose phosphate isomerase, ribulose diphosphate carboxylase, glucose-6-phosphate dehydrogenase, and phosphohexose isomerase were inhibited by NaCl concentrations far lower than that in the growth medium (3.75 m). The inhibition was reversible and was not prevented by preparing the extracts in the presence of salt. Potassium, lithium, and cesium chlorides were equally inhibitory. In contrast, whole cells require rather high levels of NaCl for optimal growth, whereas growth is inhibited by low levels of the other cations. The results suggest a specific mechanism for the exclusion of sodium from the interior of the cell. Images
253 citations
TL;DR: As cultures of Escherichia coli progressed from the exponential growth phase to the stationary growth phase, the phospholipid composition of the cell was altered, and unsaturated fatty acids were converted to cyclopropane fatty acids, and phosphatidyl glycerol appears to have been converted to cardiolipin.
Abstract: As cultures of Escherichia coli progressed from the exponential growth phase to the stationary growth phase, the phospholipid composition of the cell was altered. Unsaturated fatty acids were converted to cyclopropane fatty acids, and phosphatidyl glycerol appears to have been converted to cardiolipin. With dual isotope label experiments, the kinetics of synthesis of cyclopropane fatty acid for each of the phospholipids was examined in vivo. The amount of cyclopropane fatty acid per phospholipid molecule began to increase in phosphatidyl ethanolamine at a cell density below the density at which this increase was observed in phosphatidyl glycerol or cardiolipin. The rate of this increase in phosphatidyl glycerol or in cardiolipin was faster than the rate of increase in phosphatidyl ethanolamine. After a few hours of stationary-phase growth, all the phospholipids were equally rich in cyclopropane fatty acids. It is suggested that the phospholipid alterations observed are a mechanism to protect against phospholipid degradation during stationary phase growth. Cyclopropane fatty acid synthetase activity was assayed in cultures at various stages of growth. Cultures from all growth stages examined had the same specific activity in crude extracts.
TL;DR: It is reasoned that addition of penicillin during the period from 0 to 120 min after readdition of amino acids in the presence of lactose ought preferentially to kill RC8sr cells and enrich for relaxed mutants.
Abstract: All previously described mutants showing relaxed control of ribonucleic acid (RNA) synthesis (RCrel strains) have been derived from a common ancestor, Escherichia coli strain W6 (L. Alfoildi, G. S. Stent, and R. C. Clowes, J. Mol. Biol. 5:348, 1962), first described by E. Borek, A. Ryan, and I. Rockenbach (J. Bacteriol. 69:460, 1955). We wish to describe the isolation of independent relaxed mutants and some of their properties. The method of selection was based on the observation (L. Alfoldi et al., Z. Vererbungslehre 94:285, 1963) that, when an RCrel strain was starved of a required amino acid for 200 min in the presence of glucose and subsequently shifted to the appropriate amino acid-supplemented medium with lactose as the sole energy source, these cells experienced a lag of up to 250 min before exponential growth resumed. On the other hand, strains with stringent control (RC8tr) subjected to similar treatment resumed growth after a lag of only 40 to 60 min. We reasoned that addition of penicillin during the period from 0 to 120 min after readdition of amino acids in the presence of lactose ought preferentially to kill RC8sr cells and enrich for relaxed mutants. Reconstruction experiments with mixtures of strain W6 (RCrel) and strain CP78 (RCstr), at a ratio of 1:106, showed this approach to be workable. A derivative of E. coli K-12 W677, strain CP78, F-, RCstr, requiring threonine, leucine, histidine, arginine, and thiamine, was used for the selection of relaxed mutants. It was grown in tris(hydroxymethyl)aminomethane (Tris)-glucose medium (G. Edlin and 0. Maal0e, J. Mol. Biol. 15:428, 1966) supplemented with the requirements mentioned above, treated with ultraviolet (UV) light or nitrous acid, and then subjected to five successive rounds of the selective procedure described above; 21 independent mutants were isolated by this method. Figure la shows the uptake of uracil by the parental RCstr strain in the presence and absence of a required amino acid. Uracil uptake for the mutants appeared to fall into two broad classes: the \"high-relaxed\" mutants synthesize as much
TL;DR: The intact Krebs cycle is therefore not required for vegetative growth of aerobic Bacillis subtilis, but it is indispensable for sporulation.
Abstract: Sporulation mutants that were unable to incorporate uracil during the developmental period recovered this capacity with the addition of ribose and in most cases with the addition of glutamate. Of the mutants that responded to both ribose and glumate, all but three also responded to citrate, and all but five responded to acetate. One of the exceptional strains was deficient in aconitase and another one in aconitase and isocitrate dehydrogenase; both required glutamate for growth. For the mutants which did not respond to glutamate, the products made from (14)C-glutamate were determined by thin-layer chromatography. Significant differences were found which enabled the identification of mutant blocks. The deficiency of the corresponding enzyme activity was verified. Several mutants were deficient in alpha-ketoglutarate dehydrogenase, and one lacked succinic dehydrogenase. These mutants could still grow on glucose as sole carbon source, but not on glutamate. The intact Krebs cycle is therefore not required for vegetative growth of aerobic Bacillis subtilis, but it is indispensable for sporulation.
TL;DR: The affinity of M. pneumoniae for respiratory tract epithelium, unique among the mycoplasmas that infect man, may play a role in virulence, since this type of attachment provides an unusual opportunity for peroxide, secreted by the organism, to attack the tissue cell membrane without being rapidly destroyed by catalase or peroxidase present in extracellular body fluids.
Abstract: Monkey, rat, and chicken tracheal epithelial cells, as well as monkey, rat, guinea pig, and chicken erythrocytes, adsorbed firmly to colonies of Mycoplasma pneumoniae and M. gallisepticum. Colonies of M. pulmonis also adsorbed erythrocytes but with less avidity than M. pneumoniae or M. gallisepticum; unlike the latter organisms, M. pulmonis did not adsorb tracheal epithelial cells. Colonies of M. orale type 1 and M. orale type 3 adsorbed only chicken red cells. Other mycoplasma species tested, including four of human origin and one of animal origin, did not adsorb red cells or epithelial cells. M. pneumoniae and M. gallisepticum appeared to attach to erythrocytes or tracheal epithelial cells by neuraminic acid receptors on these cells, whereas M. orale types 1 and 3 and M. pulmonis seemed to utilize another type or other types of receptors. Pretreatment of red cells or tracheal epithelial cells with receptor-destroying enzyme, neuraminidase, or influenza B virus removed the adsorption receptors for M. pneumoniae. Similarly, pretreatment of M. pneumoniae colonies with neuraminic acid-containing materials prevented adsorption of erythrocytes or respiratory tract cells. The adsorption sites on M. pneumoniae were specifically blocked by homologous but not heterologous antisera. This property made it possible to study the nature of the mycoplasma adsorption sites by testing the capacity of different fractions of the organism to block the action of adsorption-inhibiting antibodies. Such studies suggested that the mycoplasma binding sites were probably lipid or lipoprotein in nature. The glycerophospholipid hapten was implicated as one such site, since this serologically active hapten blocked the action of hemadsorption-inhibiting antibodies in M. pneumoniae rabbit antiserum. The affinity of M. pneumoniae for respiratory tract epithelium, unique among the mycoplasmas that infect man, may play a role in virulence, since this type of attachment provides an unusual opportunity for peroxide, secreted by the organism, to attack the tissue cell membrane without being rapidly destroyed by catalase or peroxidase present in extracellular body fluids.
TL;DR: Application of fluorescent-antibody (FA) techniques to the study of rhizobia as free-living soil bacteria was explored and Antiserum to a particular strain of Rhizobium japonicum proved specific in both agglutination and FA tests.
Abstract: Application of fluorescent-antibody (FA) techniques to the study of rhizobia as free-living soil bacteria was explored. Antiserum to a particular strain of Rhizobium japonicum proved specific in both agglutination and FA tests. Within the R. japonicum group, 2 of 12 strains were stained by the conjugate and these fluoresced brightly; all others were entirely negative. FA tests were negative for 7 strains of R. meliloti, 9 strains of R. leguminosarum, 9 strains of R. trifolii, 6 strains of R. phaseoli, and 65 unidentified bacteria isolated from 12 soils. R. japonicum grew in autoclaved soil and was readily detectable by FA examination of contact slides. The FA technique also detected antibody-reacting bacteria in a field soil whose rhizobial content was unknown. Fluorescent cells were probably R. japonicum, since nodules developed on soybean plants grown in the same soil sample and FA preparations of the crushed nodules proved positive. Autofluorescence was not a problem, but nonspecific adsorption of conjugate restricted observations to microscopic fields free from soil particles. Nonspecific adsorption was substantial, irrespective of the soil used. Images
TL;DR: The nitrate reductase of Escherichia coli K-12 was localized in a particulate fraction of the cell and it sedimented as if it were bound to a large substructure that is subject to fragmentation during cell disruption procedures, interpreted as evidence for the existence of a redox-sensitive repressor which mediates nitrate reduction regulation.
Abstract: The nitrate reductase of Escherichia coli K-12 was localized in a particulate fraction of the cell and it sedimented as if it were bound to a large substructure that is subject to fragmentation during cell disruption procedures. Soluble enzyme, exhibiting a homogenous profile in sucrose gradients, was released from this fraction by an alkaline-heat treatment. Less than 1.5% of total active nitrate reductase apparently occurred in this soluble form during the course of formation of the particulate enzyme. Enzyme synthesis was repressed by aeration in the presence or absence of nitrate. Under anaerobic conditions, nitrate reductase was synthesized at a rate that could be increased 20-fold by the addition of nitrate. When enzyme synthesis was initiated by induction with nitrate or anaerobiosis, biphasic kinetics were obtained. We interpreted the results as evidence for the existence of a redox-sensitive repressor which mediates nitrate reductase regulation.
TL;DR: Seven mutants of Haemophilus influenzae were isolated by the criterion of sensitivity to ultraviolet (UV) inactivation of colony formation and the influence of acriflavine on the survival of UV-irradiated transforming DNA with these strains as recipients showed some, but by no means complete, correlation from one type of sensitivity characterization to another.
Abstract: Seven mutants of Haemophilus influenzae were isolated by the criterion of sensitivity to ultraviolet (UV) inactivation of colony formation. These mutants and the wild type were characterized with regard to X-ray inactivation of colony formation, UV induction of division inhibition, the ability of the eight strains to act as recipients to UV-irradiated H. influenzae phage and transforming deoxyribonucleic acid (DNA), and the influence of acriflavine on the survival of UV-irradiated transforming DNA with these strains as recipients. The photoreactivable sector of transforming DNA with yeast photoreactivating enzyme was measured for the most UV-sensitive mutant and was found to be greater than that of wild type. Judged by the above criteria, the order of the strains' sensitivities shows some, but by no means complete, correlation from one type of sensitivity characterization to another, indicating that a minimum of two variables is needed to explain the differences in the strains. Acriflavine increases the UV sensitivity of transforming DNA except in the most sensitive mutant. This effect is usually, but not always, more pronounced in the case of the more UV-resistant marker. The acriflavine effect is postulated to be the result of at least two factors: (i) interference with repair of transforming DNA in the host cell, and (ii) interference with the probability of recombination between transforming DNA and host DNA.
TL;DR: The results indicate that calculations from cotransfer of unlinked markers overestimates the degree of competence in highly competent populations of B. subtilis, whereas the number of plaques obtained in transfection is an under-estimate of the actual level of competence.
Abstract: Cultures of Bacillus subtilis developed competence for the uptake of deoxyribonucleic acid in a chemically defined medium with a predictable, reproducible pattern. The gross effects of individual amino acids were determined. Seven amino acids, most of which are reported to be major components of the cell wall, were shown to impair the development of maximal levels of competence. When the synthetic growth medium was supplemented with a mixture of the nine amino acids which we found to stimulate the development of competence, the level of transfection was increased to 10 to 15% of the population. The actual level of competence in these populations was assayed by transformation of unlinked bacterial markers and by two different transfection assays. The results indicate that calculations from cotransfer of unlinked markers overestimates the degree of competence in highly competent populations of B. subtilis, whereas the number of plaques obtained in transfection is an under-estimate of the actual level of competence. The results are interpreted to indicate that neither method of analysis gives a true estimate of the competent population, but that more than 80% of the cells may be competent.
TL;DR: The enzyme pattern of Saccharomyces cerevisiae was followed during batch growth and in continuous culture in a synthetic medium limited for glucose under aerobic conditions and showed to depend on the rate of substrate consumption as well as on the type of metabolism and to be correlated with the budding cycle.
Abstract: The enzyme pattern of Saccharomyces cerevisiae was followed during batch growth and in continuous culture in a synthetic medium limited for glucose under aerobic conditions. Seven enzymes were measured: succinate-cytochrome c oxidoreductase, malate dehydrogenase, nicotinamide adenine dinucleotide-linked glutamate dehydrogenase, malate synthase, isocitrate lyase, aldolase, and nicotinamide adenine dinucleotide phosphate (NADP+)-linked glutamate dehydrogenase. During fermentation of glucose and high growth rate (μ) during the first log phase in batch experiments, the first five enzymes (group I) were repressed, and aldolase and NADP+-linked glutamate dehydrogenase (group II) were derepressed. During growth on the accumulated ethyl alcohol and lower μ, the group I enzymes were preferentially formed and the other two were repressed. A sequence of derepression of the group I enzymes was found during the shift from glucose to ethyl alcohol metabolism, which can be correlated with a strong increase in the percentage of single (nonbudding) cells in the population. A correlation between the state of cells in the budding cycle and enzyme repression and derepression is suggested. In continuous culture, the enzyme pattern was shown to be related to the growth rate. The group I enzymes were repressed at high growth rates, while the group II enzymes were derepressed. Each enzyme exhibits a different dependence. The enzyme pattern is shown to depend on the rate of substrate consumption as well as on the type of metabolism and to be correlated with the budding cycle. The enzyme pattern is considered to be controlled by changes of intracellular catabolic or metabolic conditions inherent in the division cycle.
TL;DR: It was concluded that completion of a round of replication is a necessary and sufficient condition of DNA synthesis for cell division.
Abstract: When cultures of Escherichia coli B/r growing at various rates were exposed to ultraviolet light, mitomycin C, or nalidixic acid, deoxyribonucleic acid (DNA) synthesis stopped but cell division continued for at least 20 min. The chromosome configurations in the cells which divided were estimated by determining the rate of DNA synthesis during the division cycle. The cultures were pulse-labeled with 14C-thymidine, and the amount of label incorporated into cells of different ages was found by measuring the radioactivity in cells born subsequent to the labeling period. The cells which divided in the absence of DNA synthesis were those which had completed a round of chromosome replication prior to the treatments. It was concluded that completion of a round of replication is a necessary and sufficient condition of DNA synthesis for cell division.
TL;DR: It was shown that bifidobacteria convert mannitol to fructose-6-phosphate by an inducible polyol dehydrogenase and fructokinase and the phosphoroclastic enzyme could not be demonstrated in cell-free extracts.
Abstract: For six strains of Bifidobacterium bifidum (Lactobacillus bifidus), fermentation balances of glucose, lactose, galactose, mannitol, and xylose were determined Products formed were acetate, l(+)-lactate, ethyl alcohol, and formate l(+)-Lactate dehydrogenase of all strains studied was found to have an absolute requirement for fructose-1,6-diphosphate The phosphoroclastic enzyme could not be demonstrated in cell-free extracts Cell suspensions fermented pyruvate to equimolar amounts of acetate and formate Alcohol dehydrogenase was shown in cell-free extracts Possible explanations have been suggested for the differences in fermentation balances found for different strains and carbon sources By enzyme determinations, it was shown that bifidobacteria convert mannitol to fructose-6-phosphate by an inducible polyol dehydrogenase and fructokinase For one strain of B bifidum, molar growth yields of glucose, lactose, galactose, and mannitol were determined The mean value of Y (ATP), calculated from molar growth yields and fermentation balances, was 113
TL;DR: A method for effective elimination of drug resistance (R) and sex (F) factors in Escherichia coli K-12 strains by treatment with sodium dodecyl sulfate (SDS) is presented and abnormal F(+) cells which retained mating ability but showed resistance to M12 phage were isolated.
Abstract: A method for effective elimination of drug resistance (R) and sex (F) factors in Escherichia coli K-12 strains by treatment with sodium dodecyl sulfate (SDS) is presented. Growth of E. coli harboring R or F factors in Penassay Broth containing SDS led to the loss of all or part of these genetic elements. Appearance of drug-susceptible or F(-) cells among survivors was observed after the culture reached the stationary phase. Drug-susceptible cells which had lost all of their resistance markers by SDS treatment could be efficiently infected with R or F factors. Among isolated segregants which came from resistant cells, tetracycline-susceptible cells were the major segregant class. Drug-susceptible cells gave no revertants to drug resistance. By treatment of F(+) cells with SDS, unusual F(+) cells which retained mating ability but showed resistance to M12 phage were also isolated, together with mutants of another type which lost mating ability but retained sensitivity to M12 phage. Since SDS is more toxic to R(+) cells than R(-) cells, the isolation of drug-susceptible or F(-) cells under these conditions may be partly attributable to selective growth of drug-susceptible or F(-) cells in SDS-Penassay Broth.
TL;DR: Radioactive carbon assimilated by vegetative cells of Anabaena cylindrica in the light passed via an intrafilamentous route into heterocysts in the dark and after several hours, label per heterocyst approximated label per vegetative cell.
Abstract: Radioactive carbon assimilated by vegetative cells of Anabaena cylindrica in the light passed via an intrafilamentous route into heterocysts in the dark. After several hours, label per heterocyst approximated label per vegetative cell. Much of the label entering heterocysts was not available for diffusional exchange back into vegetative cells.
TL;DR: Neither diacetyl nor acetoin was formed when the otherwise complete reaction system was modified by using boiled extract or by omitting the extract, pyruvate, TPP, or the metal ions, and the ability to produce di acetyl was restored by the addition of acetyl-CoA.
Abstract: Pyruvate was shown to be the precursor of diacetyl and acetoin in Streptococcus diacetilactis, but dialyzed cell-free extracts of S. diacetilactis and Leuconostoc citrovorum that had been treated with anion-exchange resin to remove coenzyme A (CoA) formed only acetoin from pyruvate in the presence of thiamine pyrophosphate (TPP) and Mg++ or Mn++ ions. The ability to produce diacetyl was restored by the addition of acetyl-CoA. Acetyl-phosphate did not replace the acetyl-CoA. Neither diacetyl nor acetoin was formed when the otherwise complete reaction system was modified by using boiled extract or by omitting the extract, pyruvate, TPP, or the metal ions. Free acetaldehyde was not involved in the biosynthesis of diacetyl or acetoin from pyruvate, dialyzed cell-free extracts of the bacteria produced only acetoin (besides CO2) from α-acetolactate, and acetoin was not involved in the biosynthesis of diacetyl. Only one of the optical isomers present in racemic α-acetolactate was attacked by the extracts, and there was no appreciable spontaneous decarboxylation of the α-acetolactate at the pH (4.5) used in experiments.
TL;DR: On the basis of colony morphology, Gram reaction, and motility, the organism is classified as a new species of methanogenic bacterium, and the name Methanobacterium mobilis sp.
Abstract: A methanogenic bacterium, present in bovine rumen contents at concentrations of approximately 2 x 10(8) cells per ml, has been isolated in pure culture. The organism is a strictly anaerobic, weakly motile, nonsporeforming, gram-negative rod (0.7 mu x 1.5 to 2.0 mu) with rounded ends. There is a single polar flagellum. The organism grows at temperatures between 30 and 45 C, with an optimum at 40 C, and at pH values between 5.9 and 7.7, with optimal growth between pH 6.1 and 6.9. Of the 17 substrates tested, only formate and H(2) plus CO(2) supported growth. An unidentified, heat-stable factor(s) was required by the organism. The factor, which was not one of the common ones, was present in rumen fluid, mixed rumen bacteria, and yeast extract. On the basis of colony morphology, Gram reaction, and motility, the organism is classified as a new species of methanogenic bacterium, and the name Methanobacterium mobilis sp. n. is proposed.
TL;DR: The E. coli and S. aureus enzymes have been compared and it is concluded that they are identical with respect to molecular weight and pH optimum, but differ withrespect to heat stability, substrate affinity, electrophoretic mobility, and immunological reactivity.
Abstract: Chloramphenicol-resistant strains of Staphylococcus aureus contain an inducible enzyme which inactivates chloramphenicol by acetylation in the presence of acetyl coenzyme A. The products of acetylation are chromatographically indistinguishable from those obtained with chloramphenicol-resistant Escherichia coli harboring an R factor. The kinetics of induction of chloramphenicol acetyltransferase are complicated by the inducer's effect on protein biosynthesis and its fate as chloramphenicol 3-acetate, which is not an inducer of the enzyme. The E. coli and S. aureus enzymes have been compared, with the conclusion that they are identical with respect to molecular weight (approximately 78,000) and pH optimum (7.8), but differ with respect to heat stability, substrate affinity, electrophoretic mobility, and immunological reactivity. Antiserum prepared against enzyme from E. coli contains precipitating antibody, which inactivates the E. coli enzyme, but neither precipitates nor neutralizes the activity of S. aureus enzyme.
TL;DR: Six sites of 2-deoxyglucose (2DG)-induced lysis on three yeasts coincided with the regions of growth of their glucan layers, suggesting a mechanism of attack by 2DG or by its derivatives.
Abstract: Six sites of 2-deoxyglucose (2DG)–induced lysis on three yeasts (Schizosaccharomyces pombe, Pichia farinosa, and Saccharomyces cerevisiae) coincided with the regions of growth of their glucan layers. Identification of the glucan layer as the site of lysis suggests a mechanism of attack by 2DG or by its derivatives. It is proposed that the glucan layer grows by addition of glucose into internal breaks of polysaccharide molecules. 2DG inhibited resynthesis (insertion of glucose) of the broken glycosidic linkage.
TL;DR: The keratinolytic activities of dermatophytes which parasitize skin, nails, and hair have been described previously and the isolation of a keratinase from these organisms has not yet been reported.
Abstract: The keratinolytic activities of dermatophytes which parasitize skin, nails, and hair have been described previously (1, 3, 6, 8); however, the isolation of a keratinase from these organisms has not yet been reported. Trichophyton mentagrophytes var. granulosum (T. granulosum Sabouraud, 1909) was grown in a keratin medium composed of (per liter): horse hair, 2.5 g; glucose, 0.9 g; MgSO4.7H20, 0.6 g; thiamine, 0.01 g; pyridoxine 0.01 g; and inositol, 0.05 g in 0.028 M phosphate buffer (pH 7.8). Media ingredients were sterilized at 121 C and 15 psi for 20 min. After inoculation, the cultures were allowed to stand for 5 days at 25 C and then were shaken for 7 days. At the end of the growth period, the mycelium and residual hair were removed from the culture fluid by filtration. Keratinolytic activity was assayed by a modification of the method of J. J. Noval and W. J. Nickerson (4). The substrate was white guinea pig hair, Hartley strain, extracted with chloroform-methanol and air-dried. The unsterilized hair (1 to 3 mm long, 50 mg) was suspended in 0.028 M phosphate buffer containing 1 mm MgSO4 (pH 8.0) to which 45 ,ug of enzyme material was added; the final volume was 5 ml. Each assay included the following controls: (i) enzyme material in buffer solution, and (ii) hair in buffer solution. The reaction vessels, all tubes in duplicate, were incubated at 37 C for 1 hr and then were immersed in ice water for 5 min. The remaining hair was removed by filtration. Corrected absorbance values at 280 nm were con verted to keratinase units (1 KU = 0.100 corrected absorbance), and the specific activity was expressed as KU per milligram of protein. Protein contents of solutions were determined spectrophotometrically from the absorbance at 280 and at 260 nm according to the method of Layne (2). The purification of the keratinase is summarized in Table 1. The culture filtrate was passed through a diethylaminoethyl (DEAE) cellulose column (Whatman DEI) and the effluent, adjusted to pH 6.5, was transferred onto a carboxymethyl (CM) cellulose column (What-
TL;DR: Parameters affecting deoxyribonucleic acid duplex (DNA-DNA) formation on membrane filters were evaluated and the difference in thermal stabilities of heterologous and homologous DNA complexes (DeltaT'(m)) may provide a measure of divergence in nucleotide sequences.
Abstract: Parameters affecting deoxyribonucleic acid duplex (DNA-DNA) formation on membrane filters were evaluated. The reference strains used were Cytophaga succinicans strain 8, which has a guanine plus cytosine (GC) content of 38%, and Myxococcus xanthus strain FB, which has a GC content of 70%. Both organisms are gliding bacteria classified among the myxobacteria. Among the parameters evaluated, the incubation temperature used during duplex formation was found to be the most important in terms of the physical nature of the reaction product. When an incubation temperature 25 C below the melting point (Tm) of the native DNA was used, homologous duplexes exhibited a thermal stability similar to that of native DNA. At 35 C below the Tm, a considerable proportion of the duplexes were of much lower stability; at 40 C below the Tm, most of the duplexes were of much lower stability. Similar duplexes of low stability were also formed between DNA molecules from morphologically and nutritionally diverse organisms, provided the GC percentages of the DNA preparations were similar. Competition between unlabeled and labeled DNA fragments for binding sites on immobilized DNA was also greatly influenced by the incubation temperature. Heterologous DNA-DNA complexes exhibited thermal stabilities which correlated with measurements of DNA homology in experiments involving competition. In addition, the difference in thermal stabilities of heterologous and homologous DNA complexes (ΔT′m) may provide a measure of divergence in nucleotide sequences.
TL;DR: Results indicate that the formation of the assimilatory enzyme complex and that of the respiratory enzyme complex are regulated differently, and suggest that both complexes have a different composition, but that the nitrate reductase in both cases is the same protein.
Abstract: The influence of growth conditions on assimilatory and respiratory nitrate reduction in Aerobacter aerogenes was studied. The level of nitrate reductase activity in cells, growing in minimal medium with nitrate as the sole nitrogen source, was much lower under aerobic than anaerobic conditions. Further, the enzyme of the aerobic cultures was very sensitive to sonic disintegration, as distinct from the enzyme of anaerobic cultures. When a culture of A. aerogenes was shifted from anaerobic growth in minimal medium with nitrate and NH(4) (+) to aerobiosis in the same medium, but without NH(4) (+), the production of nitrite stopped instantaneously and the total activity of nitrate reductase decreased sharply. Moreover, there was a lag in growth of about 3 hr after such a shift. After resumption of growth, the total enzymatic activity increased again slowly and simultaneously became gradually sensitive to sonic disintegration. These findings show that oxygen inactivates the anaerobic nitrate reductase and represses its further formation; only after a de novo synthesis of nitrate reductase with an assimilatory function will growth be resumed. The enzyme in aerobic cultures was not significantly inactivated by air, only by pure oxygen. The formation of the assimilatory enzyme complex was repressed, however, by NH(4) (+), under both aerobic and anaerobic conditions. The results indicate that the formation of the assimilatory enzyme complex and that of the respiratory enzyme complex are regulated differently. We suggest that both complexes have a different composition, but that the nitrate reductase in both cases is the same protein.