Showing papers on "Lysis published in 1969"
TL;DR: It is infer that the complex comprises the specific portion of the cell membrane to which the DNA is attached within the cell, and this complex depends on the interaction of cell membrane components with the crystals of detergent.
239 citations
TL;DR: A mixture of hydrogen peroxide and ascorbic acid has been found to generate an antibacterial mechanism which is active against gram-negative bacteria and it is suggested that the effector mechanism involves the generation of short-lived free radicals which disturb the integrity of the cell wall.
Abstract: A mixture of hydrogen peroxide and ascorbic acid has been found to generate an antibacterial mechanism which is active against gram-negative bacteria. It results in bacterial death and renders the organism sensitive to lysis by lysozyme. Under the conditions used, horseradish peroxidase did not augment the antibacterial effect. It is suggested that the effector mechanism involves the generation of short-lived free radicals which disturb the integrity of the cell wall. This effect alone might kill bacteria by interfering with selective permeability, but in the presence of lysozyme a further bactericidal activity is accomplished by complete disruption of the cell. It is proposed that a transient antibacterial system such as that described could exist within phagocytic cells. Free radicals would be formed through the interaction of certain oxidizable substances and hydrogen peroxide, which is produced during the enhanced metabolic activity that accompanies ingestion of bacteria. Such a system would help to explain why macrophages, which are apparently devoid of preformed bactericidins, are nonetheless very efficient in killing most phagocytosed bacteria.
132 citations
TL;DR: The difference in the pH dependence of hydrolysis of chitin and cell walls appears to result from the presence of carboxyl groups in the latter substrate.
96 citations
TL;DR: A close similarity was observed between the effects of Mg-depletion on sensitivity to EDTA and to polymyxin; a relationship between their mechanisms of action is suggested.
Abstract: SUMMARY: Pseudomonas aeruginosa grown under conditions of Mg-depletion in batch eulture in simple salts medium lost sensitivity to polymyxin B, causing lysis, release of 260 nm. absorbing materials and loss of viability. The patterns of lysis and leakage produced by polymyxin were similar with regard to the effect of growth in different Mg concentrations and the inhibitory effect of high polymyxin concentrations. The rates of lysis and leakage for any one suspension were similar. There was decreased polymyxin uptake by insensitive bacteria. Addition of Mg or one of several cations restored sensitivity both to polymyxin and to EDTA to varying degrees, but only after several cell divisions had occurred. A close similarity was observed between the effects of Mg-depletion on sensitivity to EDTA and to polymyxin; a relationship between their mechanisms of action is suggested. It is proposed that cations are essential for the synthesis of sensitive components of the envelope and may themselves be involved in the structure of the component.
86 citations
TL;DR: Concentrated Sendai virus, when adsorbed to erythrocytes at 4 C, caused invaginations in the plasma membrane that led to dissolution of the virions and rupture of the cells.
Abstract: Concentrated Sendai virus, when adsorbed to erythrocytes at 4 C, caused invaginations in the plasma membrane. Following elevation of the temperature to 37 C, the plasma membrane became fused with the viral envelope before dissolution of the virions and rupture of the cells. Cell lysis was accompanied by rapid and total loss of hemoglobin to the extracellular space. Following aqueous pyridine extraction, the hemoglobin-free ghosts remaining were found to be devoid of N-acetylneuraminic acid and to have solubility properties different from those of normal erythrocyte ghosts. By the action of viral neuraminidase, bound N-acetylneuraminic acid was also liberated from purified virus receptor substance whose electrophoretic mobility was thereby substantially reduced. Cu++ selectively inhibited hemolysis and neuraminidase without interfering with hemagglutination and attachment. Neuraminidase appeared to be essential for Sendai virus hemolysis; viral particle size may also be a critical factor in this process.
79 citations
Journal Article•
TL;DR: The results suggest that human complement acted on the outer, lipoprotein—lipopolysaccharide layers of the bacterial cell wall and so gave lysozyme access to the deeper mucopeptide.
Abstract: Suspensions of Escherichia coli were not affected by lysozyme alone, but in solutions of appropriate pH and ionic strength some lysozyme was bound to the bacterial surface and remained available for action if the bacteria were subsequently treated with antibody and complement. In the presence of antibody, complement had a relatively prolonged action on E. coli ending in lysis. However, from an early stage in the reaction this lysis could be accelerated by adding lysozyme. The results suggest that human complement acted on the outer, lipoprotein—lipopolysaccharide layers of the bacterial cell wall and so gave lysozyme access to the deeper mucopeptide.
When the number of bound lysozyme molecules per bacterium was less than 10,000–20,000 the lysozyme effect decreased rapidly. However, many of these molecules may have been inactivated by K antigen.
78 citations
TL;DR: It appears that death is due to the defective synthesis of some cellular structure during phospholipid deficiency, and general damage to the membrane did not occur, and it could be that most, if not all, described effects were due to defective de novo membrane synthesis.
Abstract: The effects of oleate starvation on an oleate auxotroph of Escherichia coli K-12 were investigated. Following removal of oleate from the mutant growing in a minimal glycerol-peptone medium, the cells stopped making deoxyribonucleic acid, ribonucleic acid, protein, and phospholipids; they began to die exponentially and finally lysed. During oleate starvation in minimal medium minus peptone, inhibition of macromolecular syntheses and death occurred; however, lysis did not follow. When growth ceased, no further dying was observed. It is shown that none of the early effects (inhibition of macromolecular syntheses and death) can be due to leakiness of the cells, induction of a prophage or a colicin, or lack of energy sources. The cause of inhibition of macromolecular syntheses remained unknown. Since the rate of death was the same as the generation time under different conditions, it appears that death is due to the defective synthesis of some cellular structure (quite possibly, cytoplasmic membrane) during phospholipid deficiency. Lysis was found to require protein synthesis; electron microscopy revealed a peculiar type of “lysis from within”; i.e., the shape of the cells did not change but fragmentation of the inner layer of the cell envelope occurred. The murein was found to be unaltered. Most likely, lysis was a consequence of the cell's attempt to synthesize cytoplasmic membrane with altered phospholipid composition or during phospholipid deficiency. Several membrane functions (respiration, adenosine triphosphate formation, permeability) existing before oleate removal were not lost during starvation. Therefore, general damage to the membrane did not occur, and it could be that most, if not all, described effects were due to defective de novo membrane synthesis.
76 citations
TL;DR: Electron microscopy on thin sections of three different extremely halophilic Halobacterium species showed that their cell envelopes were of similar general construction: an inner membrane and an outer layer, consistent with the contention that high concentrations of sodium ions stabilize thecell envelopes of these organisms by neutralizing the negative charges of the protein.
Abstract: SUMMARY: Electron microscopy on thin sections of three different extremely halophilic Halobacterium species showed that their cell envelopes were of similar general construction: an inner membrane and an outer layer. The outer layer stains most strongly in the outermost part. When the NaCl concentration of the environment was lowered from the optimal of 4.3 M to 2.2 M the outer layer of the cell envelope of Halobacterium salinarium strain 1 became frayed; in many cells a release of material from the outer layer appeared to take place. When the cells were exposed to distilled water the outer layer of the envelope appeared to dissolve completely and the cell membrane disintegrated into tiny flakes. Fragments of the cell envelope produced by mechanical disintegration of the cells in 4.3 M-NaCl formed closed vesicles very rapidly; some of the cytoplasmic material became trapped inside the vesicles. Detergents appeared to slow down the closing of the vesicles and also to cause a release of material from the outer layer of the cell envelope. The cell envelope vesicles were mainly composed of protein and lipid; their content of amino sugar was low compared with the cell envelope of other Gram-negative bacteria. The cell envelope vesicle also contained nucleic acids; most of these were probably parts of the cytoplasmic material trapped inside the vesicles. The amino acid composition showed that the protein of the cell envelope vesicles was quite acidic, consistent with the contention that high concentrations of sodium ions stabilize the cell envelopes of these organisms by neutralizing the negative charges of the protein. Upon centrifugation at high speed of the lysate obtained by dialysis of the cell envelope vesicles against distilled water, the fragments of the cell membrane sedimented whereas most of the protein, presumably from the outer layer of the cell envelope, stayed in the supernatant fraction. Carotenoids and cytochromes were contained in the sediment with the membrane fragments. Most of the amino sugar-containing components stayed in the supernatant fraction; in the presence of 10-25 mM salt most of the amino sugar-containing components sediment with the membrane fragments.
73 citations
TL;DR: Velocity sedimentation at high ionic strength, of DNA released from M13-infected bacteria lysed under gentle conditions, provides a simple method for separating phage-specific DNA components from bacterial DNA.
73 citations
TL;DR: The studies presented here indicate that activation of the complement (C') system by a foreign protein will cause membrane injury and passive lysis of unsensitized erythrocytes present at the time of the reaction, and that the lysis-inducing and C'-inhibiting activity of the CV factor appear to result from similar interactions with the complement system.
Abstract: The studies presented here indicate that activation of the complement (C′) system by a foreign protein will cause membrane injury and passive lysis of unsensitized erythrocytes present at the time of the reaction. These observations suggest that in addition to the classical antibody-C′-induced cytolysis, there are alternative pathways or mechanisms for activation and participation of the terminal C′ components in the production of cell membrane injury.
We have shown that a substance derived from cobra venom and eluted from a single protein band on polyacrylamide can promote lysis of unsensitized autologous or heterologous erythrocytes in the presence of fresh guinea pig serum and that this lysis-inducing activity and C′-inhibiting activity appear to reside in the same fractions. The lytic activity is prevented by several agents known to impair classical C′3 activity, but is unaffected by certain procedures which interfere with the function of C′ components C′1 and C′2, a suggestion that this reaction involves chiefly C′3-C′9. Further, the cobra venom (CV) factor depletes C′ activity in cobra serum, and the CV factor (with its 5S serum cofactor) converts purified C′3 to its inactive form,1 indicating that the reaction of this complex with the complement system occurs without participation of antibody. Therefore, since the lysis-inducing and C′-inhibiting activity of the CV factor appear to result from similar interactions with the complement system, these observations suggest that cell membrane damage and cell lysis can be accomplished through activation of the complement system by a mechanism involving little or no participation of classical antibody or C′ components C′1, 4, or 2.
69 citations
TL;DR: By the use of polyacrylamide gel electrophoresis, the presence of five φX174 specific proteins has been shown in ultraviolet-irradiated φ X-infected cells and an additional protein is resolved by electrophoreis of dissociated phage particles.
TL;DR: The findings support the hypothesis that damage to the cell wall alone does not kill bacteria but an increase in permeability allows entry of the bactericide.
Abstract: Summary
The bactericidal potency of groups of biguanides, phenols and detergents has been compared with that of the bis-biguanide, chlorhexidine, and related to measurable effects of the compounds on bacteria. Biguanides, like chlorhexidine, precipitated bacterial cytoplasm and also lysed spheroplasts over a limited concentration range: higher concentrations prevented lysis. Certain phenols and detergents which lysed spheroplasts did not precipitate cytoplasm. All the compounds released radioactivity from isotopically labelled bacteria; at suitable concentrations, biguanides released more radioactivity than chlorhexidine, but at higher concentrations the amount of radioactivity released was reduced. Bactericidal activity correlated with both the ability to lyse spheroplasts and to precipitate cytoplasm from solution. The findings support the hypothesis that damage to the cell wall alone does not kill bacteria but an increase in permeability allows entry of the bactericide. Action of compounds on the cell wall is discussed in relation to a model of its ultrastructure.
TL;DR: It was shown that this free fatty acid is produced by the breakdown of the cellular phospholipid, not by the release of cell wall fatty acid or by the de novo synthesis of fatty acid.
TL;DR: Viral DNA continued to be synthesized up to the time of cell lysis, even though synthesis of infectious virus stopped long before this time, and cellular DNA remained stable and there was considerable, but reduced, synthesis of cellular RNA throughout the course of infection.
TL;DR: Cellular autolysis is a reflection of the level of active enzyme and not of latent enzyme, and autolysin is synthesized and mainly located in the cytoplasm as an inactive latent precursor (proenzyme) which is transported to sites on the cell wall associated with wall biosynthesis, where it becomes activated.
Abstract: A 10-hr starvation of Streptococcus faecalis ATCC 9790 for the amino acids methionine and threonine results in cells which are resistant to autolysis and which contain greatly reduced quantities of both active and latent (proteinase activable) forms of the autolytic enzyme (an N-acetyl-muramide glycanhydrolase). Cell walls were isolated from cells harvested at various times during the recovery from such starvation and were assayed for active and latent forms of the autolysin. Within 10 min of recovery the latent enzyme began to increase. Only after 30 to 60 min did the active enzyme begin to increase; after a similar lag, the cells' proneness to lysis markedly increased. The intracellular localization of both forms of the autolysin was examined, using as an experimental tool the ability of added cell wall to bind autolysin. 14C-lysine-labeled, inactivated cell walls were added to exponential-phase cells, which were then disrupted, and the mixed wall population was isolated. Measurement of the 14C release during wall autolysis indicated that the active enzyme in the cells was not available for binding to the added 14C-labeled walls and was therefore wall-bound in vivo. In contrast, up to 85% of latent autolysin activity was found to have been efficiently bound to the added 14C walls. The results obtained suggest (i) cellular autolysis is a reflection of the level of active enzyme and not of latent enzyme, and (ii) autolysin is synthesized and mainly located in the cytoplasm as an inactive latent precursor (proenzyme) which is transported to sites on the cell wall associated with wall biosynthesis, where it becomes activated.
TL;DR: It is indicated that milk lysozomes may play a significant role in the inherent anti-bacterial activity of milk.
TL;DR: Results indicate that a histidine residue or imidazolium group and a sulf-hydryl group might participate in the enzymatic hydrolysis of p-nitrophenyl β-d-xylopyranosides and lower xylo-oligosaccharide derivatives.
Abstract: A highly specific β-d-xylosidase with absolute glycon-substrate specificity was induced in Bacillus pumilus 12 by xylose. It was purified 34-fold by a procedure involving lysis of the cells with lysozyme, ammonium sulfate fractionation, G-75 Sephadex gel filtration and hydroxylapatite chromatography. The optimal activity was in the pH region 7.0–7.3. The isoelectric point was found to be 4.4. In contrast to its broad complexing affinity, the hydrolytic activity was restricted to aryl β-d-xylopyranosides and lower xylo-oligosaccharide derivatives. From the dependence of Km and Vmax on pH, it could be deduced that two dissociable groups were necessary for catalytic activity. The enzyme was competitively inhibited by Tris at pH 7.2 and proved sensitive to ionic environment. p-Chloromercuribenzoate and other SH-reagents were inhibitory but substrate analogs and competitive inhibitors protected the enzyme against inactivation by p-chloromercuribenzoate. The results indicate that a histidine residue or imidazolium group and a sulf-hydryl group might participate in the enzymatic hydrolysis of p-nitrophenyl β-d-xylopyranoside.
TL;DR: The majority of PBSH DNA molecules show a sedimentation behavior dependent on ionic strength, and it is inferred that most of the DNA molecules are less hydrodynamically rigid than native DNA having a similar average base composition and molecular weight.
Abstract: PBSH, a defective phage of Bacillus subtilis strain 168, is described. Conditions are given for optimal induction of the prophage with mitomycin C. After a latent period of 90 min, cells were lysed and phage-like particles were released with a burst size of approximately 100 to 400 phage per bacterium. Since no known host supports phage replication after infection, burst size was determined by electron microscope count. Purification procedures and criteria for purity are described. The molecular weight of deoxyribonucleic acid (DNA) extracted from PBSH was estimated by length measurement and sedimentation. No circular DNA molecules were found by either technique. PBSH DNA molecules are linear, double-stranded, and of homogeneous molecular weight, about 12 × 10 6 daltons. There is no evidence for single-strand breaks. The majority of PBSH DNA molecules show a sedimentation behavior dependent on ionic strength. It is inferred that most of the DNA molecules are less hydrodynamically rigid than native DNA having a similar average base composition and molecular weight. Possible reasons for the sedimentation behavior are discussed. Images
TL;DR: The experiments suggest that, after enzyme digestion, the cytoplasmic membrane retains a coating which is rigid in the prospheroplast but which loses rigidity when the cell is transformed into a spheroplasts.
Abstract: A strain of Saccharomyces cerevisiae which produced elongated cells under our growth conditions was investigated. By digestion of the cell walls with snail enzyme, the cells became spheroplasts after a transient state which we termed “prospheroplast.” The prospheroplast could be lysed like the spheroplast, but it retained the shape of the original yeast cell if osmotically protected. Prospheroplasts and spheroplasts were prepared, and thin sections of samples taken throughout the process of wall removal were studied in the electron microscope, at regular intervals up to the time of complete conversion to spheroplasts. In addition, cell wall remnants recovered from spheroplast preparations were shadow cast for electron microscopy. This material revealed structures resembling bud scars with attached membranous matter. The kinetic studies showed that after a certain period of time all cells were transformed into prospheroplasts, whereas spheroplast formation started later, depending on the enzyme concentration. In sections, the prospheroplasts appeared to be formed by detachment of the cell walls. Both the prospheroplasts and the spheroplasts showed asymmetric cytoplasmic membranes in which the outer leaflets appeared coated with a dense fibrillar layer. The experiments suggest that, after enzyme digestion, the cytoplasmic membrane retains a coating which is rigid in the prospheroplast but which loses rigidity when the cell is transformed into a spheroplast. Images
TL;DR: Suspensions of Streptococcus faecium, prepared by washing with and resuspending in water, were lysed slowly if sodium chloride was added prior to lysozyme; however, if brief incubation with ly sozyme was followed by addition of sodium chloride, lysis was immediate and extensive.
Abstract: Suspensions of Streptococcus faecium, prepared by washing with and resuspending in water, were lysed slowly if sodium chloride was added prior to lysozyme; however, if brief incubation with lysozyme was followed by addition of sodium chloride, lysis was immediate and extensive. Relatively lysozyme-resistant strains of S. faecalis could be lysed readily by adding lysozyme first. The primary addition of lysozyme apparently resulted in a “sensitized” cell with a damaged wall, as evidenced by N-acetylhexosamine release. Anionic detergents could replace sodium chloride in lysing these sensitized cells. The difference in activity associated with the order of addition probably involved a competition for reactive sites on the cell surface.
TL;DR: It appeared that whole spores resisted lysis because peroxide sensitive bonds were masked by compact tertiary molecular structures, and that the sensitizing agents were able to loosen these structures sufficiently to expose bonds sensitive to H2O2.
Abstract: Summary
Spores of Bacillus cereus were made sensitive to lysis with H2O2 by treatment with reagents which break disulphide bonds (e.g. thioglycollic acid), by incubation with reagents which break hydrogen bonds (e.g. urea and lithium bromide) or by incubation at high temperatures. However, treated spores lost viability in the presence of H2O2 at the same rate as did untreated spores. Lysis was optimal at high pH values and in the presence of metal ions, e.g. Cu2+, suggesting that lysis was caused by free radicals formed by metal catalysed decomposition of the peroxide. Isolated spore coats, in contrast to whole spores, were lysed by H2O2 even when not pretreated. and the immediate products of spore coat lysis were soluble proteins; on continued incubation with H2O2 these proteins were degraded to low MW peptides and amino acids. It appeared that whole spores resisted lysis because peroxide sensitive bonds were masked by compact tertiary molecular structures, and that the sensitizing agents were able to loosen these structures sufficiently to expose bonds sensitive to H2O2.
TL;DR: Differences between the catalytic activities of λ-lysozyme and egg white lysozyme on a limited group of substrates have been observed.
TL;DR: The enzymes isolated from two selected cultures of thermophilic actinomycetes-Thermomonospora fusca and Thermoactinomyces vulgaris-possess proteolytic activity were purified and showed three bands each upon cellulose acetate electrophoresis at several pH values.
Abstract: The enzymes isolated from two selected cultures of thermophilic actinomycetes—Thermomonospora fusca (A 29) and Thermoactinomyces vulgaris (A 60)—possess proteolytic activity. The enzymes were purified more than 35- to 40-fold and showed three bands each upon cellulose acetate electrophoresis at several pH values. Based upon Sephadex gel filtration, molecular weights of 21,500 and 23,800 were calculated for the active peaks of the enzymes. The purified enzymes lysed heat-killed cells of gram-positive and gram-negative bacteria, mycobacteria, and fungi and also hydrolyzed casein. The enzymes were most active between a temperature range of 60 and 70 C and pH 8.0 and 9.0, and were significantly inhibited by potassium permanganate, potassium ferricyanide, and iodine.
TL;DR: This work describes an attempt to isolate and study naturally occurring mRNA-DNA complexes from bacteria, and shows that the sedimentable mRNA fraction was the precursor for mRNA chains which appeared later in the cytoplasmic fraction.
TL;DR: Observations described here strongly suggest that cell nuclei of liver and ventral prostate have at least two forms of RNA polymerase with different specificities toward DNA templates and requirements for divalent cations.
Abstract: Widnell and Tata1 and others2,3 found that the RNA synthesizing properties of isolated mammalian cell nuclei vary depending on whether the assay system contains Mg++ (in the absence of ammonium sulphate) or Mn++ and ammonium sulphate. It is not known whether the differential effect is caused by the presence of different species of RNA polymerase or by a salt effect which may alter the action of inhibitory substances associated with nuclear DNA4 or with the polymerase5–7. Recently, we showed that liver nuclei contain a large amount of soluble RNA polymerase which can be released at 0° C without concomitant release of DNA or lysis of nuclear membranes8. During the purification of this enzyme, we observed that the ratio of the RNA polymerase activity measured in the presence of Mn++ (but no ammonium sulphate) to that determined in the presence of Mg++ was not constant among the various enzyme fractions. This and other observations described here strongly suggest that cell nuclei of liver and ventral prostate have at least two forms of RNA polymerase with different specificities toward DNA templates and requirements for divalent cations.
TL;DR: It is suggested that MMS-induced damage can be repaired but in order for cell recovery to accompany this repair, the synthesis of new DNA must be delayed until after the repair process is complete.
TL;DR: It was characteristic for the hemolysis of HK red cells by the M-antiserum the all HK cells were ultimately hemolyzed at suboptimal antibody concentrations, provided the time of incubation at 37 °C was sufficiently long, and theM-antigen appears to be expressed on all red cells of an individual HK sheep.
Abstract: Red cells of all high-potassium-type (HK) sheep and of more than one half of all low-potassium-type (LK) sheep contained the M-antigen and were hemolyzed by iso-immune anti-M antiserum in presence of a guinea pig serum complement. It was characteristic for the hemolysis of HK red cells by the M-antiserum the all HK cells were ultimately hemolyzed at suboptimal antibody concentrations, provided the time of incubation at 37 °C was sufficiently long. Thus, the M-antigen appears to be expressed on all red cells of an individual HK sheep. The M-antibody was absorbed by HK red cells and their membranes with a high affinity, whereas M-negative LK red cells and their membranes did not bind the antibody. The ratio of the number of antibody units absorbed per cell or membrane to the number of antibody units required for lysis approached unity. The amount of antibody absorbed per membrane was unaffected by ouabain in the presence of ATP, Mg++, Na+, and K+. The M-antigen activity depends on the integrity of the red cell membrane and was not detectable after lyophilization of HK membranes or in the membrane protein solubilized by n-butanol. The major M-antibody activity was found among the high molecular weight plasma proteins and may be attributed to the β2 M globulins. Heterogeneity within the antibody fraction cannot be excluded since some hemolytic activity was detected in a chromatographic fraction containing predominantly γ-globulin. The relationship between the M-antigen and the Na+−K+ transport system in sheep red cell membranes is discussed.
TL;DR: Comparative studies on a terrestrial pseudomonad with a multilayered envelope indicated that preexposure to NaCl did not enhance the susceptibility of this cell to lysis in distilled water, and the lytic susceptibility of the marine bacterium is considered to be the consequence of competition between specific monovalent cations and Mg(++) for electrostatic interactions with components of the cell envelope of this organism.
Abstract: The susceptibility of a marine bacterium, designated isolate c-A1, to lysis in distilled water and in salt solutions has been found to be a function of Na(+) concentration Optical densities of cells pre-exposed to 005 m MgCl(2) were maintained in 10 m KCl, whereas those of cells pre-exposed to 10 m NaCl were not maintained at any KCl concentration tested Cells transferred from MgCl(2) to low concentrations of NaCl underwent more extensive lysis than did those transferred to distilled water The degree of disruption of cells transferred to distilled water from mixtures of 005 m MgCl(2) and NaCl (0 to 10 m) was dependent on the concentration of NaCl; similar results were obtained with LiCl, but not with KCl In electron micrographs of thin sections, c-A1 cell envelopes consisted of two double-track layers which fractured and peeled apart on lysis after pre-exposure to NaCl-MgCl(2) mixtures Envelope eruptions or "hernias" occurred only in lysed cells pre-exposed to NaCl alone No evidence for a functional lytic enzyme was found Comparative studies on a terrestrial pseudomonad with a multilayered envelope indicated that preexposure to NaCl did not enhance the susceptibility of this cell to lysis in distilled water The lytic susceptibility of the marine bacterium is considered to be the consequence of competition between specific monovalent cations and Mg(++) for electrostatic interactions with components of the cell envelope of this organism
TL;DR: High concentrations of Mg2+ in the culture medium inhibit lysis of OX174-infected Escherichia coli C bacteria, thus yielding a 5–10-fold higher phage production, resulting in a 2–3-foldHigher phage yield.
TL;DR: Chinese hamster cells begin to die and degrade their DNA within 6 to 8 hours after 140 erg/mm2 of u.v. light, and the acid-soluble fraction of the cells contains polynucleotides, phosphorylated derivatives of thymidine and thymine.
Abstract: SummaryChinese hamster cells begin to die and degrade their DNA within 6 to 8 hours after 140 erg/mm2 and 700 erg/mm2 of u.v. light. Cell lysis releases macromolecular double-strand DNA and DNA degradative enzymes into the medium. Extracellular DNA degradation leads to an accumulation of thymidine and thymine in the medium. Intracellular degradation also occurs, and the acid-soluble fraction of the cells contains polynucleotides, phosphorylated derivatives of thymidine and thymine. Specific excision of thymine dimers in an acid-soluble form does not occur, and the contribution of DNA repair mechanisms to the observed degradation products is probably insignificant. No detectable amounts of DNA-degradation products (i.e. less than 0·05 per cent of total cellular DNA) were used for post-irradiation DNA synthesis.