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At least 469 records · Page 26Linked to original sources
PubMed1989

Dual translational initiation sites control function of the lambda S gene.

Lysis gene S of phage lambda has a 107 codon reading frame beginning with the codons Met1-Lys2-Met3. Genetic data have suggested that translational initiation occurs at both Met1 and Met3, generating two polypeptides, S107 and S105 respectively. We have proposed a model in which the proper scheduling of lysis depends on the partition of translational initiations between the two start codons. Here, using in vitro methods, we show that two stem-loop structures, one immediately upstream of the reading frame and a second approximately 10 codons within the gene, control the partitioning event. Utilizing primer-extension inhibition or 'toeprinting', we show that the two S start codons are served by two adjacent Shine-Dalgarno sequences. Moreover, the timing of lysis supported by the wild-type and a number of mutant alleles in vivo can be correlated with the ratio of ternary complex formation over Met1 and Met3 in vitro. Thus the regulation of the S gene is unique in that the products of two adjacent in-frame initiation events have opposing function.

Bacteriolysis↗
PubMed1976

Frog lysozyme. I. Its identification, occurrence as isozymes, and quantitative distribution in tissues of the leopard frog, Rana pipiens.

In the course of examining the etiology of the Lucké renal adenocarcinoma of the frog, Rana pipiens, it was found that organs of the normal adult contain bacteriolytic enzymes. These enzymes all satisfied the six criteria for the identification of lysozymes and at least eight forms were separable by polyacrylamide gel electrophoresis. Their qualitative and quantitative distribution was organ-specific. All eight isozymes were found in normal kidney, while liver and spleen contained seven forms; skin, six; ovarian egg, five; and serum, two. In quantitative assays using a radial diffusion test, spleen had the greatest lysozyme concentration, followed in descending order by kidney, liver, skin, and ovary. Serum contained very low amounts. In terms of enzyme activity per animal, ovary was the highest ranking organ. As such a large number of lysozyme isozymes has not been reported in any other organism, their origins and functions are considered in the context of their presence in an ectotherm.

Animals↗
PubMed2006

Characterization of bacteriocin HV219, produced by Lactococcus lactis subsp. lactis HV219 isolated from human vaginal secretions.

Bacteriocin HV219, produced by Lactococcus lactis subsp. lactis HV219, is active against Gram-positive and Gram-negative bacteria. Activity was lost when treated with proteolytic enzymes, SDS, Triton X-114 and Triton X-100, but not at pH 2.0 to 10.0 or after 20 min at 121 degrees C. Growth in the presence of yeast extract as sole nitrogen source yielded 3200 AU/ml. No bacHV219 activity was recorded in MRS broth with maltose, mannose, lactose or sucrose as sole carbohydrate, but fructose yielded 1600 AU/ml. K(2)HPO(4) at 10.0 g/l yielded 3200 AU/ml. Addition of 1.0 mg/l cyanocobalamin, l-ascorbic acid and thiamine to MRS broth yielded 3200 AU/ml, 1600 AU/ml and 1600 AU/ml, respectively. The mode of activity is bacteriolytic, as confirmed by atomic force microscopy.

Adult↗
PubMed1990

The virulent bacteriophage IRA of Salmonella typhimurium: cloning of phage genes which are potentially lethal for the host cell.

Morphological and biological properties of Salmonella typhimurium phage IRA were studied. The phage is a member of the Styloviridae family and exhibits a very wide spectrum of lytic activity. Molecular cloning of phage genes whose expression is lethal for the host cell has been performed and consequences of gene expression have been investigated. Expression of recombinant plasmid pKI71 causes structural changes of the cell wall and also degradation of host DNA while plasmid DNA remains intact. Expression of pKI72 blocks normal cell division. The possibility of applying such recombinant clones in marking pathways of microbial contamination in water areas is proposed.

Bacteriolysis↗
PubMed1975

A mild method for the isolation of folded chromosomes from Escherichia coli.

Until now it has not been possible to obtain nuclear bodies from Escherichia coli after treatment with rifampicin. It was generally assumed that the cross-connections between the DNA double strands which are sensitive towards ribonuclease are destroyed under the influence of inhibitors of RNA synthesis like rifampicin. In this paper a new lysis procedure is described for preparing nuclear bodies from E. coli. These particles differ in some respects, especially in salt sensitivity from those prepared by earlier methods. Using the new lysis method it is also possible to obtain folded chromosomes from cells after treatment with rifampicin. These nuclear bodies can be destroyed by ribonuclease. Therefore, it has to be postulated that a fraction of RNA being sufficient to hold the chromosome in the folded shape is not susceptible to the action of rifampicin.

Bacteriolysis↗
PubMed1975

Unfolding of the chromosome of Escherichia coli after treatment with rifampicin.

Until recently it has been assumed that the factors being responsible for the condensation of the DNA in the nucleoid of Escherichia coli are destroyed by rifampicin because it has been impossible to obtain folded chromosomes from cells treated with this inhibitor. In this paper it is shown by viscosity and sedimentation measurements that unfolding of the DNA does not take place during the process of the cell lysis as it should be predicted from this assumption, but is occurring distinctly afterwards. Since the observed unfolding process is too slow to be caused simply by molecular movements it is concluded that it is brought about by the action of salts or detergents of the lysis medium. The structure of the nucleoid is still intact in vivo despite inhibition of RNA synthesis by rifampicin.

Bacteriolysis↗
PubMed1983

Autolysis of Thermoactinomyces vulgaris spores lacking carbon dioxide during germination.

Ultrathin sections of early germinating endospores of Thermoactinomyces vulgaris were studied by electron microscope. Only spores aerated with an air-CO2 mixture (5% CO2) grow out, while spores aerated with air (0.03% CO2) lyse by the 25th min of inoculation. The lysis is due to progressive, unlimited degradation of the spore integuments and a lack of cell wall formation around the spore protoplast. The requirement of CO2 for outgrowth could not be replaced by oxaloacetate. CO2 seems to be needed to energize the dormant cytoplasmic membrane of the spore to render it capable of initiating active transport processes and of synthesizing the germ cell wall.

Bacteriolysis↗
PubMed1994

Inorganic pyrophosphatase-based detection systems. II. Detection and quantification of cell lysis and cell-lysing activity.

A novel technique, useful for detection of cell lysis and cell-lysing activity, has been developed. The method can be used for detection of cell lysis, both induced and natural, in all types of cells. The technique can be used for detection and quantification of all types of cell-lysing activities, e.g., cell wall hydrolases, toxicants, phospholipases, and antibiotics. The method relies on the detection, by a very sensitive enzymatic luminometric inorganic pyrophosphate detection assay (ELIDA; P. Nyrén and A. Lundin (1985) Anal. Biochem. 151, 504-509) of an enzyme, inorganic pyrophosphatase, which is constitutively expressed in all cells. The fraction of lysed cells in a sample can be assessed by determining the activity in the absence and in the presence of total lysing activity. The technique was used for determination of the effect of storage conditions on the intactness of two different cells, Micrococcus luteticus and Saccharomyces cerevisiae. In a model system, the approach was also used for detection of cell-lysing activity. The activity of a cell wall hydrolase (lysozyme) and a surfactant (Triton X-100) was quantified. M. luteticus cells were incubated with a specific buffer containing the lysing activity and inorganic pyrophosphate. The amount of unhydrolyzed PPi was determined by the ELIDA. The amount of PPi hydrolyzed was proportional to the amount of lysozyme present. The sensitivity of the assay was dependent on several factors, such as amount of cells used, incubation time, and incubation temperature. Lysozyme at concentrations below 5 ng/ml (< 50 pg) could be detected. The possibility of using the approach for detection of other types of cell-lysing activities is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriolysis↗
PubMed1999

A method for extraction of high-quality and high-quantity genomic DNA generally applicable to pathogenic bacteria.

In this study, we report a modified procedure for extraction of high-quality genomic DNA that is rapid, simple, biologically nonhazardous, and generally applicable to pathogenic bacteria. Bacterial cells were pretreated with 70% ethanol prior to enzymatic digestion with lysozyme. Exposure of bacterial cells to 70% ethanol sterilized the cultures, making the process biologically safe and increased the susceptibility of the cells to lysozyme-induced lysis. Consistently high yields of genomic DNA (mean average yield, 0.5-2.5 mg/ml) were obtained from 465 isolates representing over 30 clinically important bacterial species. Genomic DNA obtained was determined to be suitable for further analysis, including bacterial fingerprinting techniques like restriction endonuclease analysis, Southern hybridization, and repetitive PCR. Availability of a generally applicable procedure for extraction of high-quality and high-quantity genomic DNA would be immensely beneficial for laboratories engaged in molecular surveillance of nosocomial and community-based outbreaks.

Bacteriolysis↗
PubMed1998

Mechanism of action of the antimicrobial peptide buforin II: buforin II kills microorganisms by penetrating the cell membrane and inhibiting cellular functions.

The mechanism of action of buforin II, which is a 21-amino acid peptide with a potent antimicrobial activity against a broad range of microorganisms, was studied using fluorescein isothiocyanate (FITC)-labeled buforin II and a gel-retardation experiment. Its mechanism of action was compared with that of the well-characterized magainin 2, which has a pore-forming activity on the cell membrane. Buforin II killed Esche-richia coli without lysing the cell membrane even at 5 times minimal inhibitory concentration (MIC) at which buforin II reduced the viable cell numbers by 6 orders of magnitude. However, magainin 2 lysed the cell to death under the same condition. FITC-labeled buforin II was found to penetrate the cell membrane and accumulate inside E. coli even below its MIC, whereas FITC-labeled magainin 2 remained outside or on the cell wall even at its MIC. The gel-retardation experiment showed that buforin II bound to DNA and RNA of the cells over 20 times strongly than magainin 2. All these results indicate that buforin II inhibits the cellular functions by binding to DNA and RNA of cells after penetrating the cell membranes, resulting in the rapid cell death, which is quite different from that of magainin 2 even though they are structurally similar: a linear amphipathic alpha-helical peptide.

Anti-Bacterial Agents↗
PubMed1996

Inhibition of neutrophil function by human milk.

Human colostrum, the first product of lactation, has antioxidant properties and inhibits selected enzyme and bactericidal activities of human neutrophils. We examined the subsequent product of lactation, mature human milk, with respect to its antioxidant activities, its effects on neutrophil enzyme activities (myeloperoxidase, beta-glucuronidase, and lysozyme), and its effects on neutrophil bactericidal and phagocytic activities. Mature human milk displayed antioxidant characteristics similar to those of human colostrum, reducing cytochrome c and consuming H2O2. Mature milk also displayed colostrum-like characteristics in depressing neutrophil myeloperoxidase and beta-glucuronidase activities, but not in altering lysozyme activity. Neutrophil bactericidal activity against Staphylococcus aureus was depressed by both mature milk and colostrum, without dramatic effects on phagocytic activity. These data show that mature milk shares characteristics with human colostrum that may result in anti-inflammatory effects, but the magnitude of these effects is generally smaller.

Antioxidants↗