Microbiologia
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11840
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Resultados da Pesquisa
Item Isolation of recombinant strains with enhanced pectinase production by protoplast fusion between Penicillium expansum and Penicillium griseoroseum(Brazilian Journal of Microbiology, 2007-01) Queiroz, Marisa Vieira de; Lana, Taís Guimarães; Gonçalves, Daniel Bonoto; Araújo, Elza Fernandes de; Brito, Admilson Toscano Ribeiro de; Varavallo, Maurilio AntonioProtoplast fusion between complementary auxotrophic and morphological mutant strains of Penicillium griseoroseum and P. expansum was induced by polyethylene glycol and calcium ions (Ca2+). Fusant strains were obtained in minimal medium and a prototrophic strain, possibly diploid, was chosen for haplodization with the fungicide benomyl. Different recombinant strains were isolated and characterized for occurrence of auxotrophic mutations and pectinolytic enzyme production. The fusant prototrophic did not present higher pectinase production than the parental strains, but among 29 recombinants analyzed, four presented enhanced enzyme activities. The recombinant RGE27, which possesses the same auxotrophic and morphologic mutations as the P. griseoroseum parental strain, presented a considerable increase in polygalacturonase (3-fold) and pectin lyase production (1.2-fold).Item Development of a transformation system for Penicillium brevicompactum based on the Fusarium oxysporum nitrate reductase gene(Brazilian Journal of Microbiology, 2005-04) Queiroz, Marisa Vieira de; Pereira, Jorge Fernando; Ribeiro, Ronney Adriano; Soares, Marcos Antônio; Ribeiro, João Batista; Araújo, Elza Fernandes de; Varavallo, Maurílio AntônioPenicillium brevicompactum is a filamentous fungus that presents a potential for industrial use due its efficient pectinase production. A heterologous transformation system was developed for P. brevicompactum based on the complementation of a nitrate reductase mutant. Nitrate reductase mutants were obtained by resistance to chlorate in a rate of 23.24% when compared to other mutations that lead to the chlorate resistance. One mutant named 4457-18X was chosen for the transformation experiments with the pNH24 vector containing de Fusarium oxysporum nitrate reductase gene. A frequency of approximately 3 transformants/µg DNA was obtained using the circular vector pNH24. This frequency was multiplied about 10 fold using the linearized vector with the Xba I restriction enzyme. Southern analysis of the transformants showed a tendency of the linearized vector to diminish the number of integrations compared to the use of the circular vector. The integration was random and stable in the analyzed transformants. The establishment of a transformation system for P. brevicompactum is fundamental for genetic manipulation of this microorganism.Item Qualidade microbiológica de leite cru refrigerado e isolamento de bactérias psicrotróficas proteolíticas(Food Science and Technology, 2006-07) Martins, Maurílio Lopes; Pinto, Cláudia Lúcia de Oliveira; Vanetti, Maria Cristina DantasA estocagem do leite cru refrigerado na fonte de produção reduz perdas econômicas por atividade acidificante de bactérias mesofílicas, mas permite a seleção de bactérias psicrotróficas relacionadas a problemas tecnológicos e econômicos na indústria de laticínios. Com o objetivo de avaliar a qualidade microbiológica de leite cru, foram analisadas amostras provenientes de tanques de refrigeração individual, coletivos e do silo de uma indústria processadora de leite. Além disso, bactérias psicrotróficas proteolíticas foram isoladas do leite cru refrigerado e caracterizadas quanto à reação ao Gram e fermentação de glicose. O leite cru refrigerado mantido no silo industrial não atendeu ao padrão microbiológico legal e apresentou contagens microbianas significativamente superiores às do leite mantido em tanques individuais ou coletivos. Diferença significativa na contaminação por mesófilos e psicrotrófilos proteolíticos e não proteolíticos e por Pseudomonas foi observada entre as amostras coletadas nos tanques de refrigeração e no silo industrial. A microbiota Gram-negativa foi isolada com maior freqüência, especialmente bactérias Gram-negativas não fermentadoras de glicose.Item Integração de pAN7- 1 no genoma de Magnaporthe grisea mediada por enzima de restrição(Fitopatologia Brasileira, 2006-05) Marchi, Carlos E.; Brommonschenkel, Sérgio H.; Queiroz, Marisa V. de; Mizubuti, Eduardo S. G.Visando explorar a mutagênese insercional em Magnaporthe grisea, foram avaliadas a transformação dos protoplastos obtidos após adequação do protocolo e a eficiência da integração de pAN7-1 no genoma do ascomiceto na presença da enzima de restrição Hind III. Os protoplastos de M. grisea I-22 foram prontamente transformados para a resistência à higromicina. Quando o vetor linearizado com Hind III foi usado para transformar o fungo na presença de Hind III, a eficiência de transformação foi 1,1 a 8,1 vezes superior ao tratamento sem a adição da enzima. No geral, a melhor concentração de Hind III foi 5 unidades/reação de transformação. Tal concentração promoveu a produção média de 332 transformantes/µg de pAN7-1/107 protoplastos. A presença do gene de seleção hph no genoma de 18 indivíduos resistentes à higromicina foi confirmada por PCR.Item The glyceraldehyde-3-phosphate dehydrogenase gene of Moniliophthora perniciosa, the causal agent of witches' broom disease of Theobroma cacao(Genetics and Molecular Biology, 2009) Lima, Juliana O.; Pereira, Jorge F.; Rincones, Johana; Barau, Joan G.; Araújo, Elza F.; Pereira, Gonçalo A. G.; Queiroz, Marisa V.This report describes the cloning, sequence and expression analysis of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene of Moniliophthora perniciosa, the most important pathogen of cocoa in Brazil. Southern blot analysis revealed the presence of a single copy of the GAPDH gene in the M. perniciosa genome (MpGAPDH). The complete MpGAPDH coding sequence contained 1,461 bp with eight introns that were conserved in the GAPDH genes of other basidiomycete species. The cis-elements in the promoter region of the MpGAPDH gene were similar to those of other basidiomycetes. Likewise, the MpGAPDH gene encoded a putative 339 amino acid protein that shared significant sequence similarity with other GAPDH proteins in fungi, plants, and metazoans. Phylogenetic analyses clustered the MPGAPDH protein with other homobasidiomycete fungi of the family Tricholomataceae. Expression analysis of the MpGAPDH gene by real-time PCR showed that this gene was more expressed (~1.3X) in the saprotrophic stage of this hemibiotrophic plant pathogen than in the biotrophic stage when grown in cacao extracts.Item PCR amplification and sequence analyses of Reverse Transcriptase-like genes in Crinipellis perniciosa isolates(Fitopatologia Brasileira, 2007-09) Pereira, Jorge F.; Ignacchiti, Mariana D. C.; Araújo, Elza F.; Brommonschenkel, Sérgio H.; Cascardo, Júlio C. M.; Pereira, Gonçalo A. G.; Queiroz, Marisa V.Reverse transcriptase (RT) sequence analysis is an important technique used to detect the presence of transposable elements in a genome. Putative RT sequences were analyzed in the genome of the pathogenic fungus C. perniciosa, the causal agent of witches' broom disease of cocoa. A 394 bp fragment was amplified from genomic DNA of different isolates of C. perniciosa belonging to C-, L-, and S-biotypes and collected from various geographical areas. The cleavage of PCR products with restriction enzymes and the sequencing of various RT fragments indicated the presence of several sequences showing transition events (G:C to A:T). Southern blot analysis revealed high copy numbers of RT signals, forming different patterns among C-, S-, and L-biotype isolates. Sequence comparisons of the predicted RT peptide indicate a close relationship with the RT protein from the gypsy family of LTR-retrotransposons. The possible role of these retrotransposons in generating genetic variability in the homothallic C. perniciosa is discussed.Item Biocontrole de Listeria monocytogenes por Pediococcus acidilactici em couve minimamente processada(Food Science and Technology, 2009-10) Costa, Wanessa Altimiras; Vanetti, Maria Cristina Dantas; Puschamann, RolfEste estudo avaliou um sistema de biocontrole para inibição de Listeria monocytogenes em couve minimamente processada, objetivando sua segurança durante estocagem sob refrigeração e em condições de abuso de temperatura. O potencial inibitório de bactérias láticas tolerantes ao sal e psicrotróficas contaminantes naturais da couve e Lactobacillus plantarum, Lactobacillus delbrueckii ATCC 9649 e Lactobacillus casei CCT 1465 foram avaliadas contra L. monocytogenes. O isolado de couve identificado como P. acidilactici CCA3 inibiu L. monocytogenes a 10 e 15 °C em ágar MRS e foi selecionado como possível agente de biocontrole. O número de L. monocytogenes na couve minimamente processada aumentou 3,7 e 4,7 ciclos logarítmicos a 5 e 10 °C, respectivamente, após 20 dias de armazenamento e 4,6 ciclos logarítmicos após oito dias a 15 °C. Entretanto, quando 108 UFC.g-1 de P. acidilactici CCA3 foram inoculados no produto processado, o crescimento de L. monocytogenes reduziu 2,3 ciclos logarítmicos sob temperatura abusiva de 15 °C. A acidez titulável e as características sensoriais da couve não foram alteradas pela presença de CCA3 ao longo do período de vida útil. Estes resultados sugerem o potencial de aplicação dos bioconservantes na couve minimamente processada, que necessitam estar associados à refrigeração e sanitização para garantir segurança.Item Effect of eugenol on growth and listeriolysin O production by Listeria monocytogenes(Brazilian Archives of Biology and Technology, 2006-05) Filgueiras, Cristina Tostes; Vanetti, Maria Cristina DantasThe inhibitory effect of eugenol, a naturally occurring compound mainly present in the essential oil fraction of cloves, was studied on the growth and listeriolysin O (LLO) production by Listeria monocytogenes. Potassium efflux from cells promoted by eugenol was also determined after 24 h incubation in phosphate buffered saline. Eugenol promoted a delay on the growth of L. monocytogenes at concentrations of 100, 300 and 500 μ g mL -1 and above 800 μ g mL -1 the effect was bactericidal. Production of LLO by L. monocytogenes in the presence of eugenol was reduced 80-100%. An accumulation of external K + was observed above 300 μ g mL -1 of eugenol which indicated that the cell membrane was affected. The results showed the effectiveness of eugenol in controlling growth and LLO production of L. monocytogenes cells.Item Restriction enzyme improves the efficiency of genetic transformations in Moniliophthora perniciosa, the causal agent of witches’ broom disease in Theobroma cacao(Brazilian Archives of Biology and Technology, 2008-01) Lopes, Francis Julio Fagundes; Queiroz, Marisa Vieira de; Lima, Juliana Oliveira; Silva, Viviane Aline Oliveira; Araújo, Elza Fernandes deThe presence of restriction enzymes in the transformation mixture improved the efficiency of transformation in Moniliophthora perniciosa. The influence of the vector shape (linear or circular), the patterns of plasmid integration in genomic sites and the influence of the promoter used to express the gene marker were also analyzed. The addition of BamHI or NotI increased the number of transformants by 3-10-fold and 3-fold, respectively, over the control without added enzyme. The use of pre-linearized plasmid did not increase the transformation efficiency in comparison with the circular plasmid. However, the frequency of multi-copy transformants increased significantly. The transformation procedure here reported resulted in better production of protoplasts and transformation efficiency. In addition, the time necessary for the detection of the first transformants and the number of insertions were reduced.Item Partial purification and characterization of xylanase produced by Penicillium expansum(Brazilian Archives of Biology and Technology, 2006-05) Querido, André Luiz de Souza; Coelho, Jorge Luiz Cavalcante; Araújo, Elza Fernandes de; Chaves-Alves, Virgínia MariaAn extracellular xylanase was found to be the major protein in the filtrate culture of Penicillium expansum when grown on 0.3 % wheat bran, which showed no xylanase multiplicity. The enzime was partial purified by.ammonium sulfate fractioning, molecular exclusion chromatography, ultrafiltration and anion exchange chromatography. The protein eluation profile showed only one form of xylanase that was partially characterized. The activity of purified xylanase was optimal at pH 5.5 and 40 ºC. The enzyme was stable at pH between 5.5 and 6.5 and temperatures between 20-40 ºC. The enzyme showed a Km of 3.03 mM and Vmax of 0.027 mmol min-1 mg -1 of protein. The enzymatic activity was increased 31 % by Mg2+ and 28 % by Al3+.