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Biomedical subjects

U N Streips

Publications and source records attributed to U N Streips.

At least 37 records · Page 2Linked to original sources
PubMed1981

Transformation of a Bacillus subtilis L-form with bacteriophage deoxyribonucleic acid.

A stable L-form, sal-1, of Bacillus subtilis was transformed with deoxyribonucleic acid (DNA) from bacteriophages phi 25 and phi 29 to determine whether exogenous DNA can be introduced into this organism. The viral transformation (transfection) was successful with the use of polyethylene glycol. In the presence of the fusogen, bacteriophage phi 25 DNA initiated a single cycle of infection. When compared with transfection of competent cells of Bacillus subtilis, the appearance of viral particles was delayed and their production occurred over a longer time period. L-form cells were best able to support intracellular replication of phi 25 viral particles when in balanced growth in a rich medium. The addition of polyethylene glycol also induced infection of sal-1 with whole bacteriophage phi 25 particles which could not otherwise infect the L-form and enhanced infection by intact phi 29 particles. Primary recombination was shown to be required for polyethylene glycol-mediated phi 25 transfection, but not phi 29 transfection or for whole bacteriophage phi 25 infection mediated by polyethylene glycol. Successful transfection of sal-1 suggests that the L-form may be amenable to genetic modification with exogenous DNA.

Bacillus subtilis↗
PubMed1981

Effect of carcinogens and analogs on interferon induction.

Pretreatment of mouse embryo fibroblasts with several chemicals, including 7,12-dimethylbenz-(a)-anthracene, 2-aminofluorene, aflatoxin B1, benzo-(a)-pyrene, styrene oxide, and the No. 4 fraction of tobacco smoke condensate, resulted in severely reduced production of interferon when the cells were challenged with Newcastle disease virus. All of the above chemicals are proven or strongly suggested carcinogens. When the analogs methyl methanesulfonate, a potent carcinogen, and ethyl methanesulfonate, a weak carcinogen, were applied to cells, interferon induction was only inhibited by the methyl methanesulfonate. Therefore, carcinogens may directly inhibit the induction of interferon by Newcastle disease virus.

Animals↗
PubMed1980

R-factor responsible for an outbreak of multiply antibiotic-resistant Klebsiella pneumoniae.

Seven serotypes of Klebsiella pneumoniae isolated from different patients demonstrated resistance to the same eight antibiotics. A plasmid carrying resistance determinants to these antibiotics and mercury salts could be transferred in toto to a plasmidless strain of Escherichia coli. All E. coli transconjugants showed the same antibiotic resistance pattern. Digestion with restriction endonucleases yielded patterns that were identical for each of the R-factor transferred from the multiply resistant serotypes. Moreover, deoxyribonucleic acid-deoxyribonucleic acid hybridization demonstrated identity between the probe, pMAC20 (an R-factor from one serotype), and all R-factors isolated from the multiply resistant strains of K. pneumoniae and the E. coli transconjugants tested.

Anti-Bacterial Agents↗
PubMed1980

Extracellular proteases modify cell wall turnover in Bacillus subtilis.

The rate of turnover of peptidoglycan in exponentially growing cultures of Bacillus subtilis was observed to be sensitive to extracellular protease. In protease-deficient mutants the rates of cell wall turnover were greater than that of wild-type strain 168, whereas hyperprotease-producing strains exhibited decreased rates of peptidoglycan turnover. The rate of peptidogylcan turnover in a protease-deficient strain was decreased when the mutant was grown in the presence of a hyperprotease-producing strain. The addition of phenylmethylsulfonyl fluoride, a serine protease inhibitor, to cultures of hyperprotease-producing strains increased their rates of cell wall turnover. Isolated cell walls of all protease mutants contained autolysin levels equal to or greater than that of wild-type strain 168. The presence of filaments, or cells with incomplete septa, was observed in hyperprotease-producing strains or when a protease-deficient strain was grown in the presence of subtilisin. The results suggest that the turnover of cell walls in B. subtilis may be regulated by extracellular proteases.

Bacillus subtilis↗
PubMed1980

Chemical basis for selectivity of metal ions by the Bacillus subtilis cell wall.

The use of equilibrium dialysis techniques established that isolated cell walls of Bacillus subtilis possess selective affinities for several cations. The binding of these cations to the cell wall was influenced by the presence of various functional groups in the peptidoglycan matrix. Selective chemical modification of the free carboxyl and amino groups showed that when amino groups were replaced by neutral, bulky, or negatively charged groups, the sites available for cation complexing generally increased. Introduction of positive charges into the wall resulted in a marked decrease in the numbers of metal binding sites and usually a decrease in the apparent association constants. Both teichoic acid and peptidoglycan contribute to the sites available for interaction with metals. Hill plots of equilibrium dialysis data suggest that metal binding to cell walls involves negative cooperativity. Competition between various metals for binding sites suggested that the cations complex with identical sites on the cell walls. When the hydrogen ion concentration was increased, the affinity of the walls for metals decreased, but the numbers of metal binding sites remained constant, suggesting that cations and protons also compete for the same sites.

Bacillus subtilis↗
PubMed1980

Genetic transformation with cell wall-associated deoxyribonucleic acid in Bacillus subtilis.

Cell walls from bacillus subtilis 168 were prepared by conventional methods and found to contain deoxyribonucleic acid (DNA). In transformation assays, after autolysis, it was found that two major regions of the chromosome were selectively enriched in the wall preparations. One region clustered around the replication origin and is represented by the markers purA16, ts8132, thiC5, sacA321, and hisA1. The other region included the replication terminus with representative loci metB10, citK5, gltA292, and pyrA1. All other (internal) loci which were examined showed no statistical enrichment. The two areas of enrichment were similar to but more extensive than those reported for membrane-DNA complexes. The wall preparations also contained protein and lipid, indicating a possible membrane involvement. Analyses of the cell walls revealed that the fatty acid composition of the membrane component was not typical of the for B. subtilis protoplast membranes or for lipoteichoic acids. In addition, radioiodination of cell wall autolysates, followed by gel electrophoresis and autoradiography, demonstrated the presence of proteins not readily detectable in bulk protoplast membranes or on the surfaces of intact cells. These data suggest that a unique component of the membrane and regions of the B. subtilis genome involved in DNA replication events are tightly associated with cell walls. The binding of DNA-membrane complexes to the "rigid" cell wall and the replication of the wall could be a mechanism by which the segregation of growing chromosomes occurs.

Bacillus subtilis↗
PubMed1979

Selective association of the chromosome with membrane in a stable L-form of Bacillus subtilis.

A stalbe L-form (Sal-1) of Bacillus subtilis was found to have retained a markedly modified chromosome-membrane association when compared to intact cells. The membrane-deoxyribonucleic acid complex of the L-form was similar to that of its parental strain in quantity and stability. Genetic analysis of the L-form membrane-deoxyribonucleic acid complex revealed enrichment for markers close to the replication origin, but not for internal markers, indicating preferential attachment of the origin of chromosomal replication to the membrane. These results are in close agreement with those found for the parental bacterial form. In contrast, the replication termius region was not preferentially attached to the membrane of the L-form, even though it is enriched in the bacterial form. The association of the chromosome with the membrane at the replication terminus does not appear to be necessary for cell growth and separation, but because the L-form divides aberrantly, it may be one of the factors required for normal deoxyribonucleic acid segregation and septation.

Bacillus subtilis↗
PubMed1977

Selective enrichment for genetic markers in DNA released by competent cultures of Bacillus subtilis.

Deoxyribonucleic acid is released into the growth medium by Bacillus subtilis at the time of competence. This DNA is enriched for the genetic markers which have previously been demonstrated to be elevated in membrane-DNA preparations and more recently in cell wall-DNA complexes. Furthermore, the purA16/leu-8 relative marker enrichment varies with time, reaching its highest point at the time of maximal competence. Enrichment remains elevated for at least 60 min further in the competence regimen. Thr results suggest that certain genetic markers of the B. subtilis chromosome are preferentially more available to the external medium as the development of competence proceeds.

Bacillus subtilis↗
PubMed1976

Vinyl chloride mutagenicity via the metabolites chlorooxirane and chloroacetaldehyde monomer hydrate.

Mutagenicity tester strains of Bacillus and Salmonella were used to assay vinyl chloride in nutrient broth at a practical concentration level. Also screened without exogenous activation were seven potential metabolites of vinyl chloride in their pure forms as well as the related epichlorohydrin. Chlorooxirane, chloroacetaldehyde, chloroacetaldehyde monomer hydrate, chloroacetaldehyde dimer hydrate, chloroacetaldehyde trimer, and epichlorohydrin produced significant mutagenic acitivity in Salmonella typhimurium strains sensitive to base-pair mutation. A recombination repair deficient strain of Bacillus subtilis was inhibited in growth by these compounds, whereas excision repair deficient and wild type strains of Bacillus subtilis were relatively unaffected. On the basis of these assays a working hypothesis for the vinyl chloride carcinogenesis mechanism is proposed which involves chlorooxirane and chloroacetaldehyde monomer hydrate as the ultimate carcinogenic metabolites of vinyl chloride.

Acetaldehyde↗
PubMed1976

Comparison of various procedures for removing proteins and nucleic acids from cell walls of Bacillus subtilis.

Several procedures were used in an attempt to prepare clean cell walls from Bacillus subtilis. The results indicate that protein and nucleic acids are tightly bound to the walls. The cleanest wall preparations were found following trichloroacetic acid extraction at 60 degrees or by extraction with 0.1N NaOH under a nitrogen atmosphere for 10 hrs. Protein denaturants, such as sodium dodecyl sulfate and concentrated guanidine hydrochloride were relatively ineffective in removing proteins and nucleic acids from the cell walls. Cell wall-bound DNA was biologically active in transformation assays.

Bacillus subtilis↗
PubMed1975

Distribution of teichoic acid in the cell wall of Bacillus subtilis.

Hydrolysis of the cell wall of Bacillus subtilis 168 by autolysins or lysozyme resulted in the exposure of glucosylated teichoic acid molecules as evidenced by increased precipitation of [14C] concanavalin A. The number of concanavalin A-reactive sites increased significantly after only limited enzymatic digestion of the walls. Quantitative analyses of [14C] concanavalin A-treated wall or wall hydrolysate complexes indicate that approximately one-half of the teichoic acid molecules are surface-exposed, whereas the remainder are probably embedded within the peptidoglycan matrix. Treatment of the cell walls with sodium dodecyl sulfate or Triton X-100 did not result in new concanavalin A-reactive sites. Partial autolysis diminished the ability of the cell walls to adsorb bacteriophage phi25. Fluorescein-labeled concanavalin A bound intensely over the entire surface of growing B. subtilis 168 cells, suggesting that teichoic acid molecules are located on the total solvent-exposed surface area of the bacteria.

Adsorption↗
PubMed1975

Soluble macromolecular complexes involving bacterial teichoic acids.

Cell wall and membrane teichoic acids from several bacteria formed soluble complexes with polysaccharides and bovine plasma in alkyl alcohol solutions. Polysaccharides which contain different monomeric units and anomeric configurations complexed with the teichoic acids, suggesting that the interaction is relatively nonspecific. Teichoic acids complexed glycogen or bovine plasma albumin in 50 to 97% ethanol solutions. The macromolecular association between teichoic acids and polysaccharides or proteins was independent of teichoic acid size over a threefold molecular weight range. Glycerol phosphates or an acid hydrolysate of teichoic acid would not complex to either glycogen or bovine plasma albumin in ethanol. The optimal interaction between glycogen and the Bacillus subtilis lipoteichoic acid occurred between pH 4.5 and 8.2. The ability of teichoic acids to bind polysaccharides and proteins in moderate dielectric constant solvents suggests that these polymers may serve as complexing agents for hydrophilic molecules found in membranes.

Bacillus subtilis↗
PubMed1974

Polyelectrolyte nature of bacterial teichoic acids.

Several physicochemical properties of the teichoic acid of Bacillus subtilis 168 have been determined. The teichoic acid partial specific volume was found to be 0.57 ml/g. The apparent weight-average molecular weight of the polymer was 24,800. Sedimentation was strongly dependent on solvent. The sedimentation coefficient of the teichoic acid was found to have a value of s(20.w) (0) = 1.90S. In dilute buffers and distilled water, the teichoic acid possessed a rigid rod or extended conformation. Salts induced a loss of secondary structure in the polymer, resulting in a random coil configuration. Salt-induced structural changes in the teichoic acid were determined by viscosities, ultraviolet difference spectra, and inhibition of precipitation with concanavalin A. Divalent cations such as Mg(2+) had little effect on the teichoic acid structure. The salt-induced structural changes were reversible, as evidenced by return of the original properties upon dialysis of the teichoic acid against water. Sodium chloride inhibited the adsorption of bacteriophage ø25 to B. subtilis cell walls. Teichoic acid conformation may have a significant influence on the physiology of bacteria.

Adsorption↗
PubMed1971

Mode of action of the competence-inducing factor of Bacillus stearothermophilus.

Development of competence in the noncompetent mutant of Bacillus stearothermophilus 4S requires a soluble competence-inducing factor (CF). This study describes several observations that define the mechanism of action of this factor. (i) CF interacts with cells, protoplasts, or cytoplasmic membranes in a temperature-dependent reaction; incubation of CF with cells alters the sedimentation properties of the cells. (ii) Association between CF and the cytoplasmic membrane appears to be the first and rate-limiting step in the process of transfection with deoxyribonucleic acid (DNA) from bacteriophage TP-IC. (iii) The membrane-CF complex is capable of removing infectious DNA from the supernatant fraction in vitro. (iv) Twenty phage-resistant mutants are unable to undergo the above reactions. A model is developed in which CF serves as a dynamic mediator of the reaction between the transfecting DNA and the cell surface.

Agar↗
PubMed1971

Competence-inducing factor of Bacillus stearothermophilus.

An incompetent mutant (4S Com(-)) does not release competence-inducing factor (CF) into the culture medium and is not infected with TP-1C phage deoxyribonucleic acid (DNA) unless CF is added to the transfection assay. A TP-1C phage-resistant mutant (4S Ton-r) releases relatively large amounts of CF into the culture medium but is not infected with TP-1C phage DNA, even in the presence of CF. The production of CF by the wild type or Ton-r mutant and the ability of the wild type or Com(-) mutant to react with CF does not occur after these cultures have grown at 67 C for 1 hr or longer. A preliminary characterization of the CF is described. The autolytic enzyme or the temperate phage of the wild type and the Ton-r and Com(-) mutants do not have competence-inducing activity.

Bacillus↗