RESUMO
AIMS: The aim of this study was to examine the antimicrobial properties of novel aqueous natural rapeseed oil/saline emulsions containing different soluble components of spruce resin. METHODS AND RESULTS: The composition of aqueous resin emulsions was analysed by GC-MS and their antimicrobial properties were studied with challenge tests and with turbidometric assays. The emulsions were strongly antimicrobial against common Gram-positive and Gram-negative bacteria (including MRSA) as well as common yeasts. Furthermore, they inhibited the biofilm formation and eradicated the microbial biofilms on tested microbes. Characteristic for the emulsions was the presence of oxidized resin acids. Other main components present in emulsions, such as lignans and coumaric acids, were not antimicrobial, when tested separately. CONCLUSIONS: The results indicated that the oxidized resin acids were the antimicrobial components in the emulsions. Also, there appears to be a stoichiometric relationship between the number of resin acid molecules and the number microbe cells in the antimicrobial action. SIGNIFICANCE AND IMPACT OF THE STUDY: The fact that these solutions do not contain abietic acid, which is the main allergenic compound in resins, suggests that these solutions would be suitable, well-tolerated antimicrobials for various medical applications. The aqueous formulation will also allow the expansion of the use of these emulsions in from medical applications to the food preservatives and disinfectants.
Assuntos
Antibacterianos/farmacologia , Antifúngicos/farmacologia , Biofilmes/efeitos dos fármacos , Enterobacteriaceae/efeitos dos fármacos , Resinas Vegetais/farmacologia , Staphylococcus/efeitos dos fármacos , Traqueófitas/química , Leveduras/efeitos dos fármacos , Antibacterianos/química , Antibacterianos/isolamento & purificação , Antifúngicos/química , Antifúngicos/isolamento & purificação , Emulsões/química , Emulsões/isolamento & purificação , Emulsões/farmacologia , Enterobacteriaceae/fisiologia , Testes de Sensibilidade Microbiana , Óleo de Brassica napus/química , Resinas Vegetais/química , Resinas Vegetais/isolamento & purificação , Staphylococcus/fisiologia , Água/análise , Leveduras/fisiologiaRESUMO
AIMS: To evaluate the antagonistic effect of Pseudomonas M162 against Flavobacterium psychrophilum. METHODS AND RESULTS: The antagonistic activity of M162 was tested in vivo and in vitro, and its mode of action examined by siderophore production and immunological responses of rainbow trout (Oncorhynchus mykiss) fry. Pseudomonas M162 inhibited the growth of Fl. psychrophilum in vitro and increased the resistance of the fish against the pathogen, resulting in a relative per cent survival (RPS) of 39·2%. However, the siderophores produced by M162 did not have an inhibitory effect on Fl. psychrophilum. In fish fed with M162, the probiotic colonized the gastrointestinal tract and stimulated peripheral blood leucocyte counts, serum lysozyme activity and total serum immunoglobulin levels after 3 weeks from the start of feeding. CONCLUSIONS: This study showed the potential of Pseudomonas M162 as a probiotic by reducing the mortalities that occurred during an experimental Fl. psychrophilum infection, resulting mainly through the immunostimulatory effects of the bacterium. SIGNIFICANCE AND IMPACT OF THE STUDY: Rainbow trout fry syndrome (RTFS) causes high mortalities during the early life stages of the fish's life cycle, partly because their adaptive immunity has not yet fully developed. Thus, immunomodulation by probiotics could be an effective prophylactic method against RTFS.
Assuntos
Doenças dos Peixes/imunologia , Infecções por Flavobacteriaceae/veterinária , Flavobacterium/patogenicidade , Oncorhynchus mykiss/imunologia , Pseudomonas/imunologia , Ração Animal , Animais , Antibiose , Anticorpos Antibacterianos/sangue , Anticorpos Antibacterianos/imunologia , Doenças dos Peixes/microbiologia , Doenças dos Peixes/prevenção & controle , Infecções por Flavobacteriaceae/imunologia , Infecções por Flavobacteriaceae/microbiologia , Infecções por Flavobacteriaceae/prevenção & controle , Flavobacterium/crescimento & desenvolvimento , Flavobacterium/imunologia , Imunidade Humoral , Imunidade Inata , Imunoglobulina M/sangue , Imunoglobulina M/imunologia , Imunomodulação , Intestinos/microbiologia , Oncorhynchus mykiss/microbiologia , Probióticos/administração & dosagem , Sideróforos/imunologiaRESUMO
AIMS: To study the antagonic affect of probiotic Pseudomonas M174 on the fish pathogen Flavobacterium psychrophilum. METHODS AND RESULTS: The ability of Pseudomonas M174 to inhibit the growth of Fl. psychrophilum was examined in iron-sufficient and -deficient media. Possible siderophore production was also investigated. Antagonistic activity was confirmed in disease challenge experiments using a rainbow trout (Oncorhynchus mykiss) model. Adhesion of Pseudomonas M174 to fish surfaces and its ability to stimulate innate immunity was also investigated in vivo. Pseudomonas M174 antagonized Fl. psychrophilum and produced siderophores in vitro. In challenge experiments with Fl. psychrophilum, fish fed with Pseudomonas M174 had lower levels of mortalities than the controls. It was possible to find Pseudomonas M174 in the intestinal content of these fish after feeding and bathing with the probiotic, but probiotic was obtained from the gills only after feeding. Respiratory burst activity was also found to be enhanced in the M174 fed fish. CONCLUSIONS: These results suggest that M174 is a potential probiotic against Fl. psychrophilum and has several modes of action. SIGNIFICANCE AND IMPACT OF THE STUDY: Probiotics are a promising alternative to the use of antibiotics in aquaculture and could be a more sustainable disease control method.
Assuntos
Antibiose , Doenças dos Peixes/microbiologia , Flavobacterium/patogenicidade , Oncorhynchus mykiss/microbiologia , Probióticos , Pseudomonas/fisiologia , Animais , Aquicultura , Aderência Bacteriana , Infecções por Flavobacteriaceae/microbiologia , Infecções por Flavobacteriaceae/prevenção & controle , Infecções por Flavobacteriaceae/veterinária , Flavobacterium/metabolismo , Brânquias/microbiologia , Imunidade Inata , Intestinos/microbiologia , Oncorhynchus mykiss/imunologia , Sideróforos/biossínteseRESUMO
Fermented liquid feed has been lately much investigated in order to compensate the use of antibiotics in pig production. The fermentation process has been claimed to be the reason of the benefits associated with this type of feeding. However, contradictory results have been obtained in feeding trials due to the variable conditions in each experiment. This review focuses on the different factors that would ensure a proper fermentation with all its beneficial effects. In particular, while fermenting a liquid diet with lactic acid bacteria has been shown to improve the quality of feed and to be beneficial to the health of the animals, spontaneously fermented liquid feed appears to be unsafe for the pigs and eventually affects the consumers' safety. Consequently, the use of specific starters or inoculants to ensure the proper fermentation could be a practical solution. The regulatory status of fermented liquid feed in the EU is still unclear, but the use of specific inoculants could be considered as a special case of microbial feed additives.
Assuntos
Ração Animal/normas , Fermentação , Suínos/fisiologia , Ração Animal/microbiologia , Ciências da Nutrição Animal , Animais , União Europeia , Trato Gastrointestinal/microbiologia , Trato Gastrointestinal/fisiologiaRESUMO
Nineteen food contact papers and boards and one non-food contact board were extracted following test protocols developed within European Union funded project BIOSAFEPAPER. The extraction media were either hot or cold water, 95% ethanol or Tenax, according to the end use of the sample. The extractable dry matter content of the samples varied from 1200 to 11,800 mg/kg (0.8-35.5 mg/dm2). According to GC-MS the main substances extracted into water were pulp-derived natural products such as fatty acids, resin acids, natural wood sterols and alkanols. Substances extracted into ethanol particularly, were diisopropylnaphthalenes, alkanes and phthalic acid esters. The non-food contact board showed the greatest number and highest concentrations of GC-MS detectable compounds. The extracts were subjected to a battery of in vitro toxicity tests measuring both acute and sublethal cytotoxicity and genotoxic effects. None of the water or Tenax extracts was positive in cytotoxicity or genotoxicity assays. The ethanol extract of the non-food contact board gave a positive response in the genotoxicity assays, and all four ethanol extracts gave positive response(s) in the cytotoxicity assays to some extent. These responses could not be pinpointed to any specific compound, although there appeared a correlation between the total amount of extractables and toxicity.
Assuntos
Exposição Ambiental/efeitos adversos , Contaminação de Alimentos/análise , Embalagem de Alimentos , Papel , Animais , Bioensaio , Etanol/química , Ácidos Graxos/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Humanos , Testes de Mutagenicidade , Polímeros/química , Medição de Risco , Segurança , Esteróis/análise , Testes de Toxicidade , ÁguaRESUMO
Plasmid pVS8 (14.3 kbp) contains a 9.3 kbp fragment of Streptococcus lactis ssp. lactis SSL135 chromosomal DNA associated with the ability of this strain to grow in milk. In this study, it was found that pVS8 complements a defective plasmid-linked proteinase gene of SSL135. Using deletions and insertions, it was found that the size of the complementing region of pVS8 is approximately 6.0 kbp, and that its main part is located within a 5.7 kbp BglII fragment.
Assuntos
Endopeptidases/genética , Genes Bacterianos , Lactococcus lactis/genética , Animais , DNA Bacteriano/genética , DNA Recombinante , Endodesoxirribonucleases , Lactococcus lactis/enzimologia , Lactococcus lactis/crescimento & desenvolvimento , Lactose/metabolismo , Leite/metabolismo , Plasmídeos , Transformação BacterianaRESUMO
This paper highlights some new methods in the probiotic research based on the use of colonic biopsies and molecular biological techniques for strain identification.
Assuntos
Intestinos/microbiologia , Lactobacillus , Probióticos , Aderência Bacteriana , Fezes/microbiologia , Humanos , Intestinos/fisiologia , Reação em Cadeia da PolimeraseRESUMO
Human intestinal microflora is a complex ecosystem with hundreds of bacterial species. Its metabolic functions and interactions with the host probably affect the human health and well being, but these effects are extremely difficult to study. However, for about 100 years, the idea of modifying the composition of colonic flora by consuming viable bacteria in order to improve the quality of life and to prevent and treat intestinal disorders has had some popularity. Solid clinical data have usually been lacking to support the health claims associated with these so-called probiotics. The situation, however, is rapidly changing. Competent clinical studies are accumulating, showing that specific probiotic microbes, mainly lactic acid bacteria and bifidobacteria, can alleviate or prevent diverse intestinal disorders and reduce the risk of some intestinal diseases. Some indication of the mechanisms of action can also be deduced from the data available, while rapidly developing molecular biological methods offer new tools to verify the survival of the probiotics in the gut and the subsequent adhesion to mucosae. While development of foods containing probiotic bacteria has a great potential for the food industry and can be expected to positively affect the general health of the population, safety considerations have to be taken into account while introducing new species or strains without a previous history of safe food use.
Assuntos
Probióticos/uso terapêutico , Bifidobacterium/metabolismo , Colo/microbiologia , Neoplasias do Colo/prevenção & controle , Diarreia/terapia , Humanos , Lactobacillus/isolamento & purificação , Lactobacillus/metabolismo , Intolerância à Lactose/terapia , Probióticos/efeitos adversos , Probióticos/metabolismo , Probióticos/farmacologia , Saccharomyces/metabolismoRESUMO
The influence of oat bran oligosaccharides on carbohydrate utilization and fermentation end-products was studied with reference to three different lactic acid bacteria (LAB: Lactobacillus rhamnosus, Lactobacillus plantarum and Lactococcus lactis). The main results were that all three LAB utilized oat beta-gluco-oligosaccharides, while only L. plantarum utilized xylo-oligosaccharides. The main products of LAB metabolism were lactic acid, acetic acid, formic acid and ethanol. The results indicated that oat beta-gluco-oligosaccharides and xylo-oligosaccharides induce LAB to form the end-products of a typical mixed-acid fermentation. The formation of mixed-acid production from xylo-oligosaccharides was mainly due to the starvation of cells. This study indicates that oat bran oligosaccharides affect both qualitatively and quantitatively the fermentation end-products of LAB grown on these substrates. This should be taken into account when selecting strains for new fermented cereal based food products.
Assuntos
Avena/microbiologia , Fibras na Dieta/metabolismo , Lactobacillus/metabolismo , Lactococcus lactis/metabolismo , Oligossacarídeos/metabolismo , Ácido Acético/análise , Dióxido de Carbono/análise , Cromatografia Gasosa , Cromatografia Líquida de Alta Pressão , Cromatografia por Troca Iônica , Fibras na Dieta/microbiologia , Etanol/análise , Fermentação , Formiatos/análise , Glucanos/metabolismo , Ácido Láctico/análise , Ácido Láctico/biossíntese , Lactobacillus/crescimento & desenvolvimento , Lactococcus lactis/crescimento & desenvolvimento , Xilanos/metabolismoRESUMO
Anaerobic bacteria of the genera Megasphaera and Pectinatus cause beer spoilage by producing off flavours and turbidity. Detection of these organisms is complicated by the strict anaerobic conditions and lengthy incubation times required for their cultivation, consequently there is a need for more rapid detection methods. A polymerase chain reaction (PCR) method and a colorimetric microplate hybridization assay were developed for the rapid and specific detection of Megasphaera cerevisiae and Pectinatus spp. A biotinylated primer pair was designed for the amplification of a 403 base pair (bp) fragment of the M. cerevisiae 16S rRNA gene and a primer pair from literature was used for the amplification of an 816 bp fragment of Pectinatus 16S rRNA gene. Amplified PCR products were analyzed by the colorimetric microplate hybridization method in which a biotinylated PCR product was captured by streptavidin and hybridized with a digoxigenin-labelled oligonucleotide probe. In the final step an enzyme-linked antibody and a colorimetric reaction were utilized. A simple and rapid sample treatment was set up for the PCR detection of contaminants in beer. Detection of M. cerevisiae (> or = 5 x 10(3) colony forming units [cfu]/100 ml) and Pectinatus frisingensis (> or = 5 x 10(5) cfu/100 ml) in beer was successful, but the sensitivity of the assay still needs to be improved for direct detection of the small amounts of bacteria present in beer.
Assuntos
Cerveja/microbiologia , Microbiologia de Alimentos , Bactérias Anaeróbias Gram-Negativas/isolamento & purificação , Colorimetria , DNA Bacteriano/química , Eletroforese em Gel de Ágar , Bactérias Anaeróbias Gram-Negativas/genética , Hibridização de Ácido Nucleico , Reação em Cadeia da Polimerase/métodos , RNA/química , RNA Bacteriano/química , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genética , Sensibilidade e EspecificidadeRESUMO
The aim of the present work was to study five potential probiotic strains (Lactobacillus plantarum, two strains of L. paracasei subsp. paracasei, L. rhamnosus and Bifidobacterium sp.) comparatively in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) in vitro model, and to evaluate this model as a tool in the screening and selection of probiotic bacteria. The impact of the strains on the composition of microbiota and its metabolic activities (production of lactic acid and short-chain fatty acids) was studied. Changes in composition of the microbiota become apparent as a result of probiotic treatment. A marked, but temporary, increase was noted in the number of lactic acid bacteria and bifidobacteria. The profiles of D(-) and L(+) isomers of lactic acid detected in the SHIME after addition of probiotic strains corresponded well to those that are produced in pure culture conditions. The numbers of enterobacteriaceae decreased markedly and those of clostridia detectably during the intervention, while the enterococci tended to increase after the treatment. This pattern was similar in the reactors representing both the small and large intestine in the model. The changes in short-chain fatty acids were small, and no definite trend was observed.
Assuntos
Bifidobacterium/metabolismo , Sistema Digestório/microbiologia , Lactobacillus/metabolismo , Modelos Biológicos , Probióticos/metabolismo , Cromatografia Gasosa , Clostridium/crescimento & desenvolvimento , Colo/microbiologia , Contagem de Colônia Microbiana , Duodeno/microbiologia , Enterobacteriaceae/crescimento & desenvolvimento , Enterococcus/crescimento & desenvolvimento , Ácidos Graxos Voláteis/análise , Humanos , Íleo/microbiologia , Jejuno/microbiologia , Ácido Láctico/análiseRESUMO
Probiotics are commonly defined as viable microorganisms (bacteria or yeasts) that exhibit a beneficial effect on the health of the host when they are ingested. They are used in foods, especially in fermented dairy products, but also in pharmaceutical preparations. The development of new probiotic strains aims at more active beneficial organisms. In the case of novel microorganisms and modified organisms the question of their safety and the risk to benefit ratio have to be assessed. Lactic acid bacteria (LAB) in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus are most commonly given generally-recognised-as-safe (GRAS) status whilst members of the genera Streptococcus and Enterococcus and some other genera of LAB contain some opportunistic pathogens. Lactic acid bacteria are intrinsically resistant to many antibiotics. In many cases resistances are not, however, transmissible, and the species are also sensitive to many clinically used antibiotics even in the case of a lactic acid bacteria- associated opportunistic infection. Therefore no particular safety concern is associated with intrinsic type of resistance. Plasmid-associated antibiotic resistance, which occasionally occurs, is another matter because of the possibility of the resistance spreading to other, more harmful species and genera. The transmissible enterococcal resistance against glycopeptide antibiotics (vancomycin and teicoplanin) is particularly noteworthy, as vancomycin is one of the last effective antibiotics left in the treatment of certain multidrug-resistant pathogens. New species and more specific strains of probiotic bacteria are constantly identified. Prior to incorporating new strains into products their efficacy should be carefully assessed, and a case by case evaluation as to whether they share the safety status of traditional food-grade organisms should be made. The current documentation of adverse effects in the literature is reviewed. Future recommendations for the safety of already existing and new probiotics will be given.
Assuntos
Probióticos/efeitos adversos , Animais , Ensaios Clínicos como Assunto , Resistência Microbiana a Medicamentos , Humanos , Lactobacillus/efeitos dos fármacos , Plasmídeos , Vancomicina/farmacologiaRESUMO
The mutagenic properties of hydrazine and its mono- and di-methyl derivatives were compared by direct microbial tests with the tryptophan auxotroph Escherichia coli as indicator organism. The methyl- and dimethyl-hydrazine were also tested with metabolic activation both by the Ames plate test and by the host-mediated assay with the histidine auxotroph Salmonella typhimurium tester strains. Only hydrazine and methylhydrazine were mutagenic in direct tests, hydrazine being a far more potent mutagen that methylhydrazine. Neither methylhydrazine nor dimethylhydrazines gave positive results in the Ames tests. In host-mediated assays, symmetrical dimethylhydrazine was clearly mutagenic, whereas methylhydrazine showed marginal mutagenic activity, and unsymmetrical dimethylhydrazine was negative. Evidently the mutagenic actions of different hydrazine derivatives, though these compounds are chemically closely related, depend on different reaction mechanisms.
Assuntos
Hidrazinas/farmacologia , Mutagênicos , Avaliação Pré-Clínica de Medicamentos , Escherichia coli/genética , Técnicas Genéticas , Salmonella typhimurium/genéticaRESUMO
The mutagenic activity of 'necatorin', a strongly mutagenic compound isolated from the wild edible mushroom Lactarius necator, was studied with the Ames test, the bacterial intraperitoneal host-mediated assay and the micronucleus test. Whereas the results of the Ames tests were clearly positive, no evidence of mutagenicity was detectable in host-mediated assays or micronucleus tests.
Assuntos
Agaricales/análise , Cumarínicos/isolamento & purificação , Mutagênicos/isolamento & purificação , Mutação , Animais , Biotransformação , Núcleo Celular/efeitos dos fármacos , Eritrócitos/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos , Microssomos Hepáticos/metabolismo , Testes de Mutagenicidade , Salmonella typhimurium/efeitos dos fármacosRESUMO
Bacteria mutant at the rep gene (specifying a DNA-unwinding enzyme) were slightly more sensitive than rep+ bacteria to far ultraviolet light (ca. 254 nm; (FUV) and to monofunctional psoralen photoproducts produced with near ultraviolet light (ca. 360 nm; NUV). The enhanced sensitivity was shown in uvrA excision-deficient bacteria but not in those carrying the recA mutation. It is concluded that the rep unwinding enzyme has a small promoting effect on post-replication recombination repair. Rep- bacteria were rather more sensitive to the DNA cross-linking action f 8-methoxypsoralen (8-MOP) and NUV. This effect also was found in uvrA but not in recA bacteria. A cross-link repair pathway, dependent on both the recA+ and rep+ genes, therefore exists in addition to the pathway which depends upon the uvrAB endonuclease. Various lines of evidence suggest that the pathway operates at or after DNA replication. Exposure of rep+ bacteria to 8-MOP plus NUV did not induce any activity capable of repairing psoralen cross-links in infecting lambda phage. A possible model involving removal of the cross-link by glycosylase action at the replication fork is proposed.
Assuntos
DNA Helicases/genética , Reparo do DNA , DNA Bacteriano/efeitos da radiação , Escherichia coli/genética , Mutação , Escherichia coli/efeitos da radiação , Terapia PUVA , Fenótipo , Raios UltravioletaRESUMO
The mutagenic properties of patulin and the patulin adducts formed with cysteine were tested with histidine auxotroph Salmonella typhimurium strains as indicator organisms. The tests were performed by microsomal activation and host-mediated assay. Neither patulin nor patulin--cysteine reaction mixture was mutagenic in these test systems.
Assuntos
Mutagênicos , Patulina/farmacologia , Piranos/farmacologia , Cisteína/metabolismo , Técnicas Genéticas , Patulina/análogos & derivados , Patulina/metabolismo , Salmonella typhimurium/genéticaRESUMO
Hydrazine compounds are important industrial and laboratory chemicals. Many of them are carcinogenic in animal tests. Although the carcinogenicity is well established, the results of mutagenicity tests performed on alkylhydrazines vary greatly in different studies. In an attempt to clarify the situation we have applied Salmonella typhimurium TA102 tests to hydrazine and its mono- and dimethyl derivatives. These compounds were also tested by an Escherichia coli DNA repair-assay. The results of the repair tests indicate that unsymmetrically alkylated hydrazines can cause DNA-lesions which are lethal in repair-deficient strains. Finally QSAR (Quantitative Structure Activity Relationships) was used to develop a model to describe the genotoxic mechanism of hydrazine compounds, taking advantage of the results of previous mutagenicity studies. Energy of the lowest unoccupied molecular orbital together with octanol-water partition coefficient explains nearly completely the mutagenic activity of alkylated hydrazine compounds included in the analysis. The mutagenic activity of unsubstituted hydrazine is apparently based on different mechanisms.
Assuntos
Escherichia coli/efeitos dos fármacos , Hidrazinas/toxicidade , Mutagênicos/toxicidade , Salmonella typhimurium/efeitos dos fármacos , Dano ao DNA , DNA Bacteriano/efeitos dos fármacos , Escherichia coli/genética , Modelos Biológicos , Testes de Mutagenicidade , Salmonella typhimurium/genéticaRESUMO
Ethylenethiourea is metabolized in mice by oxidation of the sulfur atom to form 2-imidazolin-2-yl sulfenate. Ethylenethiourea itself is a carcinogen, goitrogen, teratogen and a weak bacterial mutagen. The mutagenicities of ethylenethiourea, 2-imidazolin-2-yl sulfenate and their nitroso derivatives were compared in direct bacterial tests and in the host-mediated assay. In all the test systems applied, 2-imidazolin-2-yl sulfenate was less mutagenic than the parent compound.
Assuntos
Etilenotioureia/metabolismo , Imidazóis/metabolismo , Mutagênicos , Etilenotioureia/farmacologia , Testes de Mutagenicidade , Oxirredução , Salmonella typhimurium/efeitos dos fármacos , Enxofre/metabolismoRESUMO
Ethylidene gyromitrin (acetaldehyde-N-methyl-N-formylhydrazone) is the main poisonous hydrazine derivative in the edible mushroom false morel (Gyromitra esculenta Pers. Fr.). The mutagenic properties of this compound, and of its metabolites N-methyl-N-formylhydrazine and N-methylhydrazine, were tested by microsomal activation and host-mediated assay. Histidine auxotroph strains of Salmonella typhimurium were used as indicator organisms. Microsomal preparations had no detectable effect on the biological activity of the compounds tested, but the results of host-mediated assay experiments suggested that a bacteriocidic metabolite is formed from ethylidene gyromitrin.
Assuntos
Acetaldeído/análogos & derivados , Mutagênicos , Micotoxinas/farmacologia , Acetaldeído/farmacologia , Basidiomycota , Técnicas Genéticas , Hidrazonas/farmacologia , Salmonella typhimurium/genéticaRESUMO
We report here the isolation and purification of a genotoxic antibiotic from the culture medium of a Streptomyces strain. The antibiotic was identified as actinomycin X2 by using a database search (AntiBase). In the previous studies a related compound, actinomycin D, has been shown to be non-mutagenic in the salmonella/microsome assay and several other bacterial systems. The fact that an actinomycin was detected by a bacterial repair assay seems to contradict these results. Therefore we tested several actinomycins by differential killing assay based on the same Escherichia coli strains that were used in our screening bioassays. According to our results the uvrA, recA double mutant sensitizes E. coli to the genotoxic effects of actinomycins.