Pseudomonas syringae pv. syringae B728a, an aggressive bacterial pathogen of bean, utilizes large surface populations and extracellular signaling to initiate a fundamental change from an epiphytic to a pathogenic lifestyle. Extracytoplasmic function (ECF) sigma (σ) factors serve as important regulatory factors in responding to various environmental signals. Bioinformatic analysis of the B728a genome has revealed 10 ECF sigma factors, five of which have high levels of sequence similarity to the FecI-type of ECF sigma factors and play a known role in the regulation of various iron transport systems. Because iron is essential for the induction of major virulence factors in B728a, I hypothesized that these FecI-type sigma factors may play a critical role in the bacterium’s transition between lifestyles. Deletion mutants of two FecI-type sigma factors, Psyr_1040 and Psyr_1107, in B728a have been created using homologous recombination based on the phage λ Red recombinase method. This study shows that the B728a FecI-type sigma factors, Psyr_1040 and Psyr_1107 are affected by conditions of iron stress, and influence the expression of putative outer membrane receptors and transmembrane sensors associated with these genes. Moreover, Psyr_1107 contributes to the expression of a cluster of predicted pili assembly genes downstream of it. Mutations in Psyr_1040 and Psyr_1107 affect the population levels of B728a in bean plants, since in planta growth of deletion mutants of B728a lacking Psyr_1040 and Psyr_1107 appears to be slower than wild-type B728a. In this thesis, the possible roles of Psyr_1040 and Psyr_1107 in the adaptation of B728a to a pathogenic lifestyle are addressed using a combination of phenotypic characterization and quantitative real-time PCR (qRT-PCR) analyses.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-24T15:08:49Z No. of bitstreams: 1 Myrzania de Lira Guerra.pdf: 1530658 bytes, checksum: 73ad27186e300f4bbcd6fd5b19977dd1 (MD5) / Made available in DSpace on 2017-03-24T15:08:49Z (GMT). No. of bitstreams: 1 Myrzania de Lira Guerra.pdf: 1530658 bytes, checksum: 73ad27186e300f4bbcd6fd5b19977dd1 (MD5) Previous issue date: 2015-07-24 / Xanthomonas campestris pv. viticola (Xcv) is the causal agent of grapevine bacterial canker. In the Submédio do Vale São Francisco in the northeast of Brazil, bacterial canker is one of the most important grapevine diseases, responsible for severe damage and representing a serious risk to Brazilian viticulture and wine production. The aims of this study were to: a) evaluate the ability of seven Xcv strains to adhere and form biofilms in vitro and to determine the influence of the culture medium and surfaces on biofilm formation, besides to study the biofilm architecture and swarming motility; and b) optimize a method of protein extraction for proteomic analysis of the Xcv, comparing the efficiency of four methods, based on the twodimensional gel electrophoresis profile (2D-PAGE). All the strains adhered to the wells of the polystyrene microtiter plate and formed biofilms in all liquid culture medium (nutrient brothdextrose- yeast extract, yeast extract-dextrose-calcium carbonate, KADO 523 and Luria-Bertani), though to different degrees (weak, moderate and strong). In glass tubes, only Xcv229 and Xcv158 strains formed biofilms. We identified Xcv229 as a strong biofilmproducing strain. Using confocal laser scanning microscopy (CLMS) only Xcv229 showed an initial matrix of biofilm structure after 24 h of growth. Scanning electron microscopy (SEM) images of strains Xcv229 and Xcv158 grown for 36 h on microtiter plates revealed typical biofilm architectures. Strain Xcv158 displayed a higher swarming motility than Xcv229, showing that in this case, biofilm formation is not motility-dependent. This is the first report of biofilm production by the bacterial plant pathogen Xcv. Trizol®, Phenol, Centrifugation and Lysis methods were tested and through quantitative and qualitative analysis, the most suitable method to obtain high-quality protein was selected. All methods enabled the extraction of a significant amount of proteins; nevertheless, the centrifugation method allowed obtaining the highest concentration of solubilized proteins. However, the analysis of the 2D-PAGE gel images revealed a larger number of spots in the lysis method when compared to the others. Taking into consideration the quality of the results and the practical advantages of the lysis method, this is recommended as the best option for total protein extraction of Xcv for proteomic studies. / Xanthomonas campestris pv. viticola (Xcv) é o agente causal do cancro bacteriano da videira. No Submédio do Vale São Francisco, no nordeste do Brasil, o cancro bacteriano é uma das doenças mais importantes dessa cultura, sendo responsável por grandes prejuízos, o que representa um sério risco para a viticultura brasileira. Os objetivos deste estudo foram: a) avaliar a capacidade de sete isolados de Xcv para aderir e formar biofilmes in vitro e determinar a influência do meio de cultura e das superfícies na formação de biofilme, além de investigar a arquitetura do biofilme e motilidade swarming; e b) otimizar um protocolo para extração de proteínas para análise da proteômica de Xcv, comparando a eficiência de quatro métodos com base no perfil de eletroforese em gel bidimensional (2D-PAGE). Todos os isolados aderiram aos poços da placa de microtitulação de poliestireno e formaram biofilmes nos meios de cultura líquidos testados (caldo nutriente-dextrose-extrato de levedura, extrato de levedura-dextrose-carbonato de cálcio, KADO 523 e Luria-Bertani), em níveis fraco, moderado e forte. Em tubos de vidro, apenas os isolados Xcv229 e Xcv158 formaram biofilmes. Xcv229 foi considerado um forte produtor de biofilme. Na microscopia confocal a laser (MCL) apenas em Xcv229 visualizou-se a matriz inicial da estrutura do biofilme, após 24 h de crescimento. As imagens da microscopia eletrônica de varredura (MEV) de Xcv229 e Xcv158 crescidos durante 36 h em placas de microtitulação revelaram arquiteturas típicas de biofilme. O isolado Xcv158 apresentou uma maior motilidade swarming do que Xcv229, mostrando que, neste caso, a formação de biofilme é independente da motilidade. Este é o primeiro relato de produção de biofilme bacteriano pela fitobactéria Xcv. Os métodos Trizol®, fenol, centrifugação e lise foram analizados quantitativa e qualitativamente, para selecionar o mais adequado na obtenção de proteína de alta qualidade. Todos permitiram a extração de uma quantidade significativa de proteínas, no entanto, o método de centrifugação resultou numa maior concentração de proteínas solubilizadas. A análise das imagens do gel 2D-PAGE revelou um maior número de spots no método de lise, quando comparado com os outros. Levando-se em consideração a qualidade dos resultados e as vantagens práticas do método de lise, este é recomendado como a melhor opção para extração de proteínas totais de Xcv para estudos de proteômica.

No description available.

Serratia sp. ATCC 39006 (S39006) is known for producing carbapenem and prodiginine antibiotics; 1-carbapen-2-em-3-carboxylic acid (car) and prodigiosin. It displays different motility mechanisms, such as swimming and swarming aided by flagellar rotation and biosurfactant production. In addition, S39006 produces gas vesicles to float in aqueous environments and enable colonization of air-liquid interfaces. Gas vesicles are thought to be constructed solely from proteins expressed from a gene cluster composed of two contiguous operons, gvpA1-gvpY and gvrA-gvrC. Prior to this study, three cognate regulators, GvrA, GvrB, and GvrC, encoded by the right hand operon were known to be essential for gas vesicle synthesis. Post-transcriptional regulators such as RsmA-rsmB were also known to be involved in the inverse regulation of gas vesicles and flagella based motility. Furthermore, gas vesicle formation, antibiotic production, and motility in S39006 were affected by cell population densities and de-repressed at high cellular densities through a quorum sensing (QS) system. The aim of this research study was to identify novel regulatory inputs to gas vesicle production. Mutants were generated by random transposon mutagenesis followed by extensive screening, then sequencing and bioinformatic identification of the corresponding mutant genes. After screening, 31 mutants and seven novel regulatory genes impacting on cell buoyancy were identified. Phenotypic and genetic analysis revealed that the mutations were pleiotropic and involved in cell morphology, ion transport and central metabolism. Two new pleiotropic regulators were characterized in detail. Mutations in an ion transporter gene (trkH) and a putative transcriptional regulator gene (floR) showed opposite phenotypic impacts on flotation, flagella-based motility and prodigiosin, whereas production of the carbapenem antibiotic was affected in the transcription regulator mutant. Gene expression assays with reporter fusions, phenotypic assays in single and double mutants, and proteomics suggested that these regulatory genes couple different physiological inputs to QS and RsmA-dependent and RsmA-independent pathways.