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A J Garro

Publications and source records attributed to A J Garro.

At least 37 records · Page 2Linked to original sources
PubMed1978

Correlated genetic and EcoRI cleavage map of Bacillus subtilis bacteriophage phi105 DNA.

The seven previously identified EcoRI cleavage fragments of phi 105 DNA were ordered with respect to their sites of origin on the phage genome by marker rescue. One fragment, H, did not carry any determinants essential for replication. This fragment was totally missing in a deletion mutant which exhibited a lysogenization-defective phenotype. There is a nonessential region on the phi 105 genome which begins in fragment B, spans fragment H, and ends in fragment F. The size of the nonessential region, as estimated by alterations observed in the fragmentation patterns of deletion mutant DNAs, is approximately 2.7 X 10(6) daltons. Two new EcoRI cleavage fragments with molecular weights of approximately 0.2 X 10(6) were detected by autoradiography of 32P-labeled DNA. These small fragments were not located on the cleavage map.

Bacillus subtilis↗
PubMed1977

Fragmentation of Bacillus bacteriophage phi105 DNA by complementary single-stranded DNA in the cohesive ends of the molecule.

The structure of DNA from the temperate Bacillus subtilis phage phi105 was examined by using the restriction endonuclease EcoRI and by sedimentation analysis. The DNA contains six EcoRI cleavage sites. Although eight DNA fragments were identified in the EcoRI digests, the largest of these was shown to consist of the two fragments that carry the cohesive ends of the phage DNA. In neutral gradients, the majority of whole phi105 DNA sedimented as nicked circles and the remainder as oligomers. No unit-length linear structures were detected. The associated cohesive ends could be sealed by DNA ligase from Escherichia coli and could be cleaved by S1 nuclease. On the basis of these results and previously reported studies, it appears that, as isolated from phage particles, phi105 DNA is a circular molecule that is formed from the linear structure by the association of complementary single-stranded DNA.

Bacillus subtilis↗
PubMed1976

Effects of cytochrome p-448 and p-450 inducers on microsomal dimethylnitrosamine demethylase activity and the capacity of isolated microsomes to activate dimethylnitrosamine to a mutagen.

The relationship between microsomal dimethylnitrosamine (DMN) demethylase activity and the capacity of isolated hepatic microsomes to activate DMN to a mutagen was examined using microsomes from C57 and DBA/2 mice which had been exposed to three different types of microsomal enzyme inducers: phenobarbital, which induces cytochrome P-450, 3-methylcholanthrene, which induces cytochrome P-448, and the polychlorinated biphenyl, Aroclor 1254 which appears to induce both types of cytochromes. DNM induced mutagenesis was assayed by a Salmonella auxotroph reversion test. With the C57 mice all three inducers increased both the activity of microsomal DMN demethylase and the capacity of the microsomes to activate DMN mutagenicity. In each case, however, the increase in mutagenicity was disproportionately greater than the increase in DMN demethylase activity. This was particularly evident with microsomes prepared from Aroclor induced mice. Microsomes from 3-methylcholanthrene treated DBA/2 mice were not induced for DMN demethylase or the activation of DMN mutagenicity. In addition the capacity of Aroclor to function as an inducer was relatively poor in this strain. Both DMN demethylation and mutagenesis were inhibited by the addition of either SKF 525-A or benzo (a)pyrene to the reaction mixtures. Thus microsomal activation of DMN to a mutagen and DMN demethylase appear to involve both cytochromes P-450 and P-448.

Animals↗
PubMed1976

Vinyl chloride dependent mutagensis: effects of liver extracts and free radicals.

The mutagenic effects of vinyl chloride (VC) on Salmonella typhimurium strain TA1530 are enhanced by mouse or rat liver extracts. The extracts prepared from mice pretreated either with vinyl chloride or the microsomal enzyme inducer, Aroclor 1254, did not produce any greater stimulation of VC-dependent mutagenesis than extracts from untreated animals. These same extracts, however, differed markedly in their capacity to stimulate the mutagenicity of dimethylnitrosamine (DMN), a compound which is converted to a mutagen by an NADPH dependent microsomal mixed function oxidase. The order of activity of the extracts with DMN was Aroclor pretreated is greater than untreated is greater than VC pretreated. Furthermore, the stimulatory effect of the liver extracts on VC mediated mutagenesis did not require NADPH and was still evident in liver extracts in which the microsomal mixed function oxidase system had been heat inactivated. The mutagenic activity of VC also was found to be stimulated by riboflavin in the presence of light suggesting that free radicals may be involved in VC dependent mutagenesis.

Aroclors↗
PubMed1975

Cytochrome P-450 in the activation and inactivation of carcinogens.

The capacity of isolate mouse liver microsomes to alter the mutagenicity for bacteria of the primary carcinogen N-methyl-N'-nitro-N-nitrosoguanisine (MNNG) and the secondary one dimethylnitrosamine (DMN) was studied. Microsomal activation of DMN and inactivation of MNNG were decreased by protein- and protein-cholinedeficient diets and were increased by pretreatment with microsomal enzyme inducers. The decrease and increase paralleled the content of cytochrome P-450 present in the different microsomal preparations. With human liver microsomes of differing cytochrome P-450 contents similar correlation was obtained, whereas normal rat liver microsomes did not activate or inactivate DMN or MNNG. Oxidative demethylation of DMN by mouse liver microsomes and the activation of DMN to a mutagen followed similar kinetics. Both reactions were inhibited by carbon monoxide and the inhibition was maximally reversed by monochromatic light at 450 nm. These observations indicate that at least some carcinogens are activated or inactivated by the unspecific cytochrome P-450 dependent enzyme system, suggesting that the extent of this biotransformation may be one factor influencing human carcinogenesis.

Animals↗
PubMed1975

Bacteriophage-specific protein synthesis during induction of the defective Bacillus subtilis bacteriophage PBSX.

Particles of PBSX, a defective, noninfectious phage which is inducible from strains of Bacillus subtilis 168, contain at least seven structural proteins resolvable by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Five of these proteins are associated with the phage tail and two with the phage head. An eighth protein, which also may be coded for by the PBSX prophage, has been identified in cells derepressed for PBSX replication.

Autoradiography↗
PubMed1975

Isolation and characterization of prophage mutants of the defective Bacillus subtilis bacteriophage PBSX.

Bacillus subtilis mutants with lesions in PBSX prophage genes have been isolated. One of these appears to be a regulatory mutant and is defective for mitomycin C-induced derepression of PBSX; the others are defective for phage capsid formation. All of the PBSX structural proteins are synthesized during induction of the capsid defective mutants; however, several of these proteins exhibit abnormal serological reactivity with anti-PBSX antiserum. The two head proteins X4 and X7 are not immunoprecipitable in a mutant which fails to assemble phage head structures. In the tail mutant, proteins X5 and X6 are not immunoprecipitable, tails are not assembled, and a possible tail protein precursor remains uncleaved. The noninducible mutant does not synthesize any PBSX structural proteins after exposure to mitomycin C. The mutation is specific for PBSX since ø105 and SPO2 lysogens of the mutant are inducible. All of the known PBSX-specific mutations were shown to be clustered between argC and metC on the host chromosome. In addition, the metC marker was shown to be present in multiple copies in cells induced for PBSX replication. This suggests that the derepressed prophage replicates while still integrated and that replication extends into the adjacent regions of the host chromosome.

Antigen-Antibody Complex↗
PubMed1974

Relationship between lysogeny, spontaneous induction, and transformation efficiencies in Bacillus subtilis.

The low transformation efficiency of Bacillus subtilis 168 lysogenic for phages ø105 or SPO2 is shown to result from the induction of lytic phage replication in competent cells. Lysogenic competent cells have a higher rate of spontaneous prophage induction than noncompetent cells. Mutants of ø105 and SPO2 which form lysogens resistant to spontaneous induction were isolated, and these lysogens exhibited higher transformation levels than those formed by wild-type phage. These results suggest that the physiological state of competence in B. subtilis promotes prophage derepression leading to cell death and the loss of potential transformants.

Bacillus subtilis↗
PubMed1973

Isolation and properties of Bacillus subtilis strains lysogenized by a clear plaque mutant of bacteriophage phi 105.

A clear plaque mutant of the temperate Bacillus phage phi105 lysogenized a small fraction of infected cells forming an integrated prophage at or near the normal phi105 insertion site. These lysogens exhibited a spontaneous induction rate approximately 1,000-fold lower than wild type and were noninducible (ind(-)) by mitomycin C. Prophage was induced, however, when competent cultures were incubated with transforming DNA. The ind(-) phenotype could not be attributed solely to the clear plaque mutation and appears to involve a cell-specific factor. Lysogenization by the clear plaque mutant, in contrast to wild-type phage, did not cause a marked reduction in transformation efficiency.

Bacillus subtilis↗
PubMed1973

DNA-mediated prophage induction in Bacillus subtilis lysogenic for phi 105c4.

Prophage was induced when strains of Bacillus subtilis 168 lysogenic for phi105c4 were grown to competence and exposed to specific bacterial DNAs. The time course of phage production was similar to that observed for mitomycin C induction of wild-type prophage. Induction was directly dependent upon DNA concentration up to levels which were saturating for the transformation of bacterial auxotrophic markers. The extent of induction varied with the source of DNA. The burst of phage induced by DNA isolated from a W23 strain of B. subtilis was fivefold less than that induced by DNA from B. subtilis 168 strains, while B. licheniformis DNA was completely inactive. This order of inducing activity was correlated with the ability of the respective DNAs to transform auxotrophic markers carried by one of the phi105c4 lysogens. Differences in inducing activity also were observed for different forms of phi105 DNA. The DNAs isolated from phi105 phage particles and phi105c4 lysogens were inactive, whereas DNA from cells lysogenized by wild-type phi105 induced a burst of phage. When tested for transforming activity, however, both phi105c4 and phi105 lysogen DNAs were equally effective. An induction mechanism which involves recombination at the prophage insertion site is proposed to explain these differences.

Bacillus subtilis↗