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M Llagostera

Publications and source records attributed to M Llagostera.

31 records · Page 2Linked to original sources
PubMed1991

Expression of nrdA and nrdB genes of Escherichia coli is decreased under anaerobiosis.

By using plasmid nrdA-lacZ, nrdAB-lacZ, and nrdB-lacZ gene fusions, the expression of nrdA and nrdB genes of Escherichia coli under anaerobiosis has been studied. The results obtained show that cells of E. coli growing under either fermentative or nitrate respiring conditions present a lower basal level of both nrdA and nrdB genes transcription from the nrdPA promoter. On the other hand, transcription of the nrdB gene from the internal nrdPB promoter was not affected by the absence of oxygen. Moreover, the DNA damage-mediated inducing factor of these nrd genes was the same in both aerobic and anaerobic cultures.

Aerobiosis↗
PubMed1990

Induction of SOS genes in Escherichia coli and mutagenesis in Salmonella typhimurium by fluoroquinolones.

The induction of several SOS genes of Escherichia coli by fluoroquinolones has been studied. Three different SOS gene fusions (recA::lacZ, umuC::lacZ and sulA::lacZ) have been introduced into the E.coli MC1061 strain to study the induction of these SOS genes in the same genetic background. Data on the basal level of expression of these fusions, as well as their induction by mitomycin C and N-methyl-N'-nitro-N-nitrosoguanidine are presented. Using these strains, we have found that, like nalidixic acid, ofloxacin, enoxacin and ciprofloxacin are strong inducers of the SOS genes tested, umuC gene expression being the highest. Furthermore, fluoroquinolones produced a significant increase in the reversion of the base substitution hisG428 mutation in the TA102 Salmonella tester strain, while no effect was found in strains TA98, TA100, TA1537 and TA1535. These data indicate that the error-prone repair pathway can participate in mutagenesis induced by fluoroquinolones and also that the damage produced by these chemicals may be similar to that produced by nalidixic acid.

DNA Repair↗
PubMed1988

Regulation of ubiG gene expression in Escherichia coli.

To study the regulation of the expression in Escherichia coli of the ubiG gene, which codes for the last enzyme in the pathway of ubiquinone biosynthesis, a fusion between the ubiG and lacZ genes was constructed in vitro. The results showed that (i) the expression of the ubiG gene was higher under aerobic conditions than under anaerobic growth conditions, (ii) the presence of glucose in the culture medium decreased the transcription of the ubiG gene, and (iii) cya and crp mutants exhibited lower levels of ubiG gene expression than the wild-type strain. The addition of cyclic AMP increased the expression of the ubiG gene in both cya and wild-type strains but not in a crp mutant. This fact suggests that the cyclic AMP receptor protein-cyclic AMP complex positively modulates ubiG gene transcription. It was also determined that the transcription of the ubiG gene was in the counterclockwise direction on the E. coli map.

Carbon↗
PubMed1987

Influence of S9 mix in the induction of SOS system by quercetin.

The induction of recA, umuC and sfiA genes by quercetin was studied in the presence and in the absence of S9 mix. The inducing activity of quercetin is higher for sfiA than for recA and umuC genes in the absence of S9 mix. The putative genotoxic metabolites of quercetin produced by S9 mix display different inducing activities of the three SOS genes as compared to quercetin. The induction of sfiA gene is decreased by the presence of S9 mix, whereas an opposite effect was observed concerning umuC and recA. These data suggest that the error-prone repair pathway participates in mutagenesis by quercetin and its metabolites. Moreover, the type of DNA damage exerted by quercetin seems to be determined by its metabolic fate. The importance of testing for the induction of other SOS genes, together with sfiA, in the study of SOS functions as a genotoxic index is emphasized.

Animals↗
PubMed1987

DNA repair systems in the phototrophic bacterium Rhodobacter capsulatus.

UV irradiation and mitomycin C exposure trigger a protease-activity-dependent inhibition of cell division in Rhodobacter capsulatus, which begins about 2 h after the treatment is applied. UV irradiation also induces a dose-dependent mutagenesis with a maximal rate between 5 and 10 J m-2, with increased synthesis of a protein of Mr approximately 30,000 between 2 and 3 h after UV irradiation. In addition, R. capsulatus has an efficient photoreactivation system that reverses the lethal effects of UV irradiation in the presence of intense visible light.

Cell Division↗
PubMed1986

Induction of SOS genes of Escherichia coli by chromium compounds.

The induction of several SOS genes of Escherichia coli such as recA, umuC, and sfiA by hexavalent (K2Cr2O7, K2CrO4, and CrO3) and trivalent (CrCl3, Cr(NO3)3, and (CH3COO)3Cr) compounds of chromium was studied. Induction was measured as beta-galactosidase activity, using lacZ gene fusions under the control region of different SOS genes. The hexavalent chromium forms induced the genes responsible for massive synthesis of RecA protein, error-prone repair, and inhibition of cell division. On the other hand, the trivalent chromium compounds were unable to induce any of the SOS genes tested. Individual assay of hexavalent chromium compounds showed that K2Cr2O7 was a stronger inducing agent of those three SOS genes tested than K2CrO4, which, in turn, was stronger than CrO3. All this data led to the conclusion that hexavalent chromium compounds, but not trivalent, are proficient agents of induction of the SOS system and can produce indirect mutagenesis in Escherichia coli.

Cell Division↗
PubMed1986

Expression of the SOS system in Escherichia coli growing under nitrate respiration conditions.

Induction of several SOS functions by mitomycin C, bleomycin or thermal treatment of a recA441 mutant growing under nitrate respiration conditions was studied in Escherichia coli. Mitomycin C caused inhibition of cell division, induction of prophages and expression of umuC gene but like in aerobically growing cells, it did not trigger the cessation of cell respiration. On the contrary, both recA+ and recA441 cultures either treated with bleomycin or incubated at 42 degrees C failed to induce any of the different SOS functions cited above. Furthermore, after bleomycin addition or thermal treatment both recA+ and recA441 cultures did not present any variation in the cellular ATP level, contrary to what happens under aerobic growth. The blocking of the expression of some SOS functions under nitrate respiration conditions is not an irreversible process because cells incubated under these anaerobic conditions were able to induce the SOS system when changed to an aerobic medium 30 min after the SOS-inducing treatment had been applied.

Adenosine Triphosphate↗
PubMed1986

Characterization of SE1, a new general transducing phage of Salmonella typhimurium.

A transducing phage, SE1, which is able to infect Salmonella typhimurium was isolated from a Salmonella enteritidis strain. SE1 is a temperate phage which is heteroimmune with respect to phages P22, L, KB1 and ES18. It is similar in morphology and size to phages P22, L and KB1 and is serologically related to phages P22 and L but not to KB1. Efficiencies of generalized transduction effected by phage SE1 are similar to those for P22HT (int7), a mutant which mediates a high frequency of chromosomal gene transduction. The lengths of chromosomal DNA transduced by SE1 and P22HT (int7) are similar. Furthermore, the SE1 prophage does not exclude the transducing particles from cells it has lysogenized; consequently it is possible to use both SE1 lysogens and non-lysogenic strains as recipients in SE1-mediated transduction experiments, and obtain similar transduction efficiencies. However, the SE1 prophage gives rise to a lysogenic conversion that decreases the rate of adsorption of SE1 and L phages by about 50%, but does not affect adsorption of P22. Altogether these results suggest that phage SE1 may be a useful tool in the genetic manipulation of S. typhimurium.

Antigens, Bacterial↗
PubMed1985

Effect of adenine, cytidine and guanosine on the expression of the SOS system in Escherichia coli.

Addition of cytidine or guanosine to UV-irradiated cells of a RecA+ strain of Escherichia coli did not produce any effect on the induction of two SOS functions: inhibition of cell division and expression of the umuC gene. Under the same conditions adenine gave a slight increase in the induction of these two responses. In a RecA441 mutant growing at 42 degrees C, both cytidine and guanosine inhibited these SOS functions, whereas adenine produced a large increase in their expression. Moreover, the ATP concentration of the RecA441 mutant at 42 degrees C showed a decrease which occurred earlier in the cells growing in the presence of cytidine or guanosine than in the absence of either compound. Adenine induced an increase of about three times the initial ATP concentration of this mutant at 42 degrees C which dropped quickly after 10 min. Neither cytidine nor guanosine increased the evolution of cellular ATP in UV-irradiated cells of the RecA+ strain, whereas adenine had only a slight positive effect. However, in UV-irradiated RecA+ cells with and without adenine, ATP levels dropped quickly to the initial value after 20 min. These data suggest that the influence of adenine, cytidine and guanosine on the expression of the RecA441 phenotype at 42 degrees C may be due to alteration of the cellular ATP concentration of this mutant.

Adenine↗
PubMed1985

Expression of the SOS genes of Escherichia coli in Salmonella typhimurium.

To lysogenize Salmonella typhimurium by Lambda phage, a region of 10.2 kb of Escherichia coli DNA carrying the nusA gene was cloned in a S. typhimurium strain containing a F'112 plasmid which codifies for the lamB region of E. coli. The strain of S. typhimurium obtained in this way, was lysogenized by lambda c IndO- bacteriophage harboring either a fusion between recA1 or sfiA genes of E. coli with lacZ gene. Likewise, pSE143 plasmid with a umu C::lacZ fusion was introduced in S. typhimurium. Afterwards, induction of these SOS genes was studied. Results obtained show that the basal transcription of both recA and sfiA genes of E. coli was higher in S. typhimurium than in E. coli. Nevertheless, induction of recA and sfiA genes by UV-irradiation and mitomycin C was higher in E. coli than in S. typhimurium. On the other hand, umuC gene of E. coli presents the same basal level of transcription in both E. coli and S. typhimurium species, although induction of this gene by UV-irradiation and mitomycin C was higher in S. typhimurium than in E. coli. Therefore, the plasmid pUA25 constructed in this work may be used to introduce, using the Lambda phage as a vector, the SOS genes of E. coli in other bacterial species which may be useful to study the relationship between their respective SOS systems.

Bacterial Proteins↗
PubMed1984

Changes in ATP concentration in Escherichia coli during induction of the SOS system by mitomycin C and bleomycin.

Treatment of Escherichia coli with bleomycin induced a dramatic increase in ATP concentration in the first 30 min. Afterwards, in RecA+ strains, ATP dropped quickly to values similar to those of untreated cells. Mutants of E. coli defective in either RecA protein or RecA protease activity did not show this decrease, indicating that it was due to the action of RecA protease. The increase in ATP in the first 30 min was dependent on RecBC exonuclease activity and must have been due to substrate level phosphorylation, since an uncoupler such as dinitrophenol did not affect it. Nevertheless, mitomycin C did not induce any change in ATP pools of RecA+ strains, at least during 120 min following treatment. The implications of these findings are discussed in relation to the possible pathways of activation of RecA protease.

Adenosine Triphosphate↗
PubMed1984

[Multiple clear-cell acanthoma].

Clear cell acanthoma is a benign tumor reported by Degos et al. in 1962. Most commonly the acanthoma presents as a solitary nodule on the lower limb in late middle-aged persons. We've found only 11 papers about multiple clear cell acanthoma. We describe a 73 years old patient who had 21 lesions, the highest number found in the literature.

Aged↗