RESUMO
Bacteria isolated from marine sponges found off the coast of Rio de Janeiro, Brazil, were screened for the production of antimicrobial substances. We report a new Pseudomonas putida strain (designated P. putida Mm3) isolated from the sponge Mycale microsigmatosa that produces a powerful antimicrobial substance active against multidrug-resistant bacteria. P. putida Mm3 was identified on the basis of 16S rRNA gene sequencing and phenotypic tests. Molecular typing for Mm3 was performed by RAPD-PCR and comparison of the results to other Pseudomonas strains. Our results contribute to the search for new antimicrobial agents, an important strategy for developing alternative therapies to treat infections caused by multidrug-resistant bacteria.
Assuntos
Animais , Antibacterianos/farmacologia , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Poríferos/microbiologia , Pseudomonas putida/química , Antibacterianos/biossíntese , Antibacterianos/isolamento & purificação , Testes de Sensibilidade Microbiana , Oceanos e Mares , Filogenia , Pseudomonas putida/genética , Pseudomonas putida/isolamento & purificação , Técnica de Amplificação ao Acaso de DNA Polimórfico , RNA Bacteriano/genética , /genéticaRESUMO
This study analyzed the involvement of tetA and tetE genes in the tetracycline resistance of 16 strains of genus Aeromonas, isolated from clinical and food sources. Polymerase chain reactions revealed that 37.5 percent of the samples were positive for tetA, and also 37.5 percent were tetE positive. One isolate was positive for both genes. Only the isolate A. caviae 5.2 had its resistance associated to the presence of a plasmid, pSS2. The molecular characterization of pSS2 involved the construction of its restriction map and the determination of its size. The digestion of pSS2 with HindIII originated two fragments (A and B) that were cloned separately into the pUC18 vector. The tetA gene was shown to be located on the HindIII-A fragment by PCR. After transforming a tetracycline-sensitive strain with pSS2, the transformants expressed the resistance phenotype and harbored a plasmid whose size was identical to that of pSS2. The results confirmed the association between pSS2 and the tetracycline resistance phenotype, and suggest a feasible dissemination of tetA and tetE among strains of Aeromonas. This study suggests the spreading tetA and tetE genes in Aeromonas in Brazil and describes a resistance plasmid that probably contributes to the dissemination of the resistance.
Assuntos
Aeromonas/efeitos dos fármacos , Antibacterianos/farmacologia , Antiporters/genética , Proteínas de Bactérias/genética , Lactuca/microbiologia , Resistência a Tetraciclina/genética , Tetraciclina/farmacologia , Aeromonas/genética , Aeromonas/isolamento & purificação , Cromossomos Bacterianos/genética , Testes de Sensibilidade Microbiana , Fenótipo , Reação em Cadeia da PolimeraseRESUMO
Mutantes auxotróficos e Nif de Bacillus azotofixans foram isolados a partir de culturas tratadas com EMS, empregando-se um método de enriquecimento com penicilina, desenvolvido para este microrganismo. A frequência de obtençäo de mutantes auxotróficos (0,19 por cento) foi cerce de três vezes maior do que a de obtençäo de mutantes Nif(0,063 por cento), embora ambas as frequências fossem extremamente baixas. Os fatores de crescimento exigidos pelos mutantes auxotróficos incluiam aminoácidos (47,05 por cento), bases nitrogenadas (17,64 por cento) ou vitaminas (11,76 por cento). Estes mutantes seräo posteriormente usados em experimentos de transferência gênica, realizados com o objetivo de se localizar os genes nif no cromossomo desse microrganismo