Surface enhanced Raman spectroscopy (SERS) is highly promising analytical technique for trace detection of analytes. It is particularly well suited for environmental analyses due to its high sensitivity, specificity, ease of operation and rapidity. The detection and characterization of environmental contaminants, using SERS is highly related to the uniformity, activity and reproducibility of the SERS substrate. In this thesis, SERS substrates were produced by gold nanoparticle formation on wax patterned chromatography paper. In situ reduction of hydrogen tetrachloroaurate (gold precursor) by trisodium citrate dihydrate (reducing agent) was used to produce gold nanoparticles within a paper matrix. These gold nanoparticle based SERS substrates were analyzed by FE-SEM, UV-Vis and Raman spectroscopy. This work discusses the SERS signal enhancements for Raman active MGITC dye for a series of substrates prepared by in situ reduction of gold salt and pre-produced gold nanoparticles. UV-Vis analysis was performed to understand the effect of different molar ratio (reducing agent to gold precursor) and reaction time on the size and shape of the localized surface plasmon resonance (LSPR) band that dictates the SERS enhancements. It was concluded that lower molar ratio (1:1 and 2:1) of citrate-to gold produced better SERS signal enhancements and broader LSPR band. Therefore, use of lower molar ratio (MR) was recommended for paper-based substrates using in situ-based reduction approach. / Master of Science

Background: To allow an immediate treatment of an infection with suitable antibiotics and bactericides or fungicides, there is an urgent need for fast and precise identification of the causative human pathogens. Methods based on DNA sequence comparison like 16S rRNA analysis have become standard tools for pathogen verification. However, the distinction of closely related organisms remains a challenging task. To overcome such limitations, we identified a new genomic target sequence located in the single copy gene for tRNA nucleotidyltransferase fulfilling the requirements for a ubiquitous, yet highly specific DNA marker. In the present study, we demonstrate that this sequence marker has a higher discriminating potential than commonly used genotyping markers in pro- as well as eukaryotes, underscoring its applicability as an excellent diagnostic tool in infectology. Results: Based on phylogenetic analyses, a region within the gene for tRNA nucleotidyltransferase (CCA-adding enzyme) was identified as highly heterogeneous. As prominent examples for pro- and eukaryotic pathogens, several Vibrio and Aspergillus species were used for genotyping and identification in a multiplex PCR approach followed by gel electrophoresis and fluorescence-based product detection. Compared to rRNA analysis, the selected gene region of the tRNA nucleotidyltransferase revealed a seven to 30-fold higher distinction potential between closely related Vibrio or Aspergillus species, respectively. The obtained data exhibit a superb genome specificity in the diagnostic analysis. Even in the presence of a 1,000-fold excess of human genomic DNA, no unspecific amplicons were produced. Conclusions: These results indicate that a relatively short segment of the coding region for tRNA nucleotidyltransferase has a higher discriminatory potential than most established diagnostic DNA markers. Besides identifying microbial pathogens in infections, further possible applications of this new marker are food hygiene controls or metagenome analyses.

Background: To allow an immediate treatment of an infection with suitable antibiotics and bactericides or fungicides, there is an urgent need for fast and precise identification of the causative human pathogens. Methods based on DNA sequence comparison like 16S rRNA analysis have become standard tools for pathogen verification. However, the distinction of closely related organisms remains a challenging task. To overcome such limitations, we identified a new genomic target sequence located in the single copy gene for tRNA nucleotidyltransferase fulfilling the requirements for a ubiquitous, yet highly specific DNA marker. In the present study, we demonstrate that this sequence marker has a higher discriminating potential than commonly used genotyping markers in pro- as well as eukaryotes, underscoring its applicability as an excellent diagnostic tool in infectology. Results: Based on phylogenetic analyses, a region within the gene for tRNA nucleotidyltransferase (CCA-adding enzyme) was identified as highly heterogeneous. As prominent examples for pro- and eukaryotic pathogens, several Vibrio and Aspergillus species were used for genotyping and identification in a multiplex PCR approach followed by gel electrophoresis and fluorescence-based product detection. Compared to rRNA analysis, the selected gene region of the tRNA nucleotidyltransferase revealed a seven to 30-fold higher distinction potential between closely related Vibrio or Aspergillus species, respectively. The obtained data exhibit a superb genome specificity in the diagnostic analysis. Even in the presence of a 1,000-fold excess of human genomic DNA, no unspecific amplicons were produced. Conclusions: These results indicate that a relatively short segment of the coding region for tRNA nucleotidyltransferase has a higher discriminatory potential than most established diagnostic DNA markers. Besides identifying microbial pathogens in infections, further possible applications of this new marker are food hygiene controls or metagenome analyses.

A cana-de-açúcar, é atualmente a cultura mais plantada no estado de São Paulo, apresentando grande importância no setor agrícola. Assim como qualquer outra cultura, é hospedeira de uma série de patógenos que podem limitar sua produção. A bactéria fastidiosa Leifsonia xyli subsp. xyli (Lxx) é o agente causal do raquistismo-das-soqueiras (RSD) em canade- açúcar cujo o principal sintoma é a redução acentuada do crescimento observada em plantas adultas. Essa doença é de difícil diagnose pois a evolução dos sintomas é lenta devido à natureza fastidiosa da bactéria. Lxx pode ser considerada como um endófíto obrigatório que cresce a níveis patogênicos nos tecidos da planta dependendo de estímulos bióticos e abióticos. Devido à importância da cultura e aos danosoCasionados pela Lxx, este trabalho apresentou dois enfoques principais: o primeiro foi o desenvolvimento de um protocolo para quantificação de Lxx em tecido de cana-de-açúcar por meio da técnica de PCR quantitativo em tempo real; o segundo foi o estudo da interação entre cana-de-açúcar e Lxx, em busca de uma melhor compreensão da evolução desse processo através da identificação de proteínas que apresentaram alteração em abundância ao longo do tempo em função da colonização pela bactéria em duas variedades de cana (RB835486 e SP80-3280) e em seguida enfatizando o sistema antioxidante nesta relação. Para isso, foram desenvolvidos primers específicos para detecção de Lxx que permitiram quantificar baixos níveis bacterianos em tecido foliar, revelando diferenças entre variedades segundo a cinética do crescimento bacteriano. Plantas com diferentes títulos bacterianos obtidas mediante inoculação artificial ou não foram submetidas à análise proteômica por meio da técnica de 2D-DIGE, uma vez que para o RSD, os danos estão relacionados à alta colonização de Lxx em seus tecidos. Os resultados alcançados com o sequenciamento de proteínas que apresentaram alteração em abundância revelaram que, em plantas da variedade RB835486 observou-se repressão de proteínas da via de estresse oxidativo e metabolismo primário, em contraste com a variedade SP80-3280, que apresentou aumento da abundância de proteínas relacionadas à via de estresse oxidativo, ambas para o mesmo tratamento, em plantas não inoculadas artificialmente. Já em plantas inoculadas com Lxx foram identificadas alteração na abundância de proteínas relacionadas ao crescimento da planta, ciclo celular, vias de sinalização celular e hormonal, esses resultados são consistentes com o principal sintoma da doença, o raquitismo, pois indica que as alterações temporais observadas na expressão de proteínas relacionadas com o aumento do título de Lxx in planta podem resultar em alterações do equilíbrio hormonal e menor crescimento da planta. Alguns resultados observados com a análise bioquímica corroboram com os dados acima descritos, pois a variedade RB835486 apresentou uma resposta precoce ao estresse oxidativo e mostrou maior controle do crescimento bacteriano, o que pode estar relacionado ao balanço de ERO\'s (espécies reativas de oxigênio) utilizadas pelo metabolismo como sinalizador celular na interação planta-patógeno. Em contraste, a variedade SP80-3280, em sua maioria, apresentou indução da atividade de enzimas antioxidantes mais tardiamente, momento em que a bactéria Lxx apresentou os maiores títulos de crescimento. / Sugarcane is currently the most grown crop in the state of São Paulo, with great importance in the agricultural sector. Like every crop, sugarcane is host to a number of pathogens that may limit its production. The fastidious bacterium Leifsonia xyli subsp. xyli (Lxx) is the causal agent of ratoon stunting in sugarcane (RSD), which the main symptom is a sharp reduction in growth observed in adult plants, this disease is difficult to diagnose because the evolution is slow due to nature of fastidious bacteria. Lxx can be considered as an obligatory endophyte that grows at pathogen levels in plant tissues depending on biotic and abiotic stimuli. Due to the importance of culture and the damage caused by the Lxx, this work presents two main approaches: the first one was the development of a protocol for the quantification of Lxx in sugarcane tissue by quantitative real time PCR; the second one was to study the interaction between sugarcane and Leifsonia xyli subsp. xyli aiming to a better understanding of the evolution of this process, identifying alterations in abundance of proteins over time depending on the bacterial colonization in the two varieties of sugarcane (RB835486 and SP80-3280) and then, emphasizing the antioxidant system in this relationship. Thus, we developed specific primers that enabled Lxx quantification at low bacterial levels in leaf tissue. The assay showed differences among sugarcane varieties according to the kinetics of bacterial growth. Plants that presented different titers of bacteria were obtained by artificial inoculum or not were selected to proteomic analysis by 2D-DIGE technique, since for RSD, the damage is related to high colonization in plant tissues. The identification of sugarcane proteins revealed that for variety RB835486 were observed a repression of stress proteins and proteins related to primary metabolism, in contrast with SP80-3280 variety, which it was identified high abundance of proteins of oxidative stress pathway, in not inoculated plants, for both varieties. However in inoculated plants it was identified a change in the abundance of proteins related to plant growth, cell cycle, cell signaling and hormonal pathways. These results corroborate with the main symptom of the disease, ratton, and suggest that temporal changes in expression of sugarcane cited proteins by increasing title of Lxx can result in hormonal imbalance and the decrease of plant growth. The major part of biochemistry analyzes corroborate with previous data obtained in proteomic approach. The RB835486 variety showed an early response to oxidative stress and suggests a greater control of bacterial growth in its tissues, which may be related to the balance of ERO\'s in signaling metabolism in plant pathogen interaction. While the SP80-3280, showed a later induction of antioxidant enzymes, when the bacterium Lxx had the highest titer of bacteria.

A cana-de-açúcar, é atualmente a cultura mais plantada no estado de São Paulo, apresentando grande importância no setor agrícola. Assim como qualquer outra cultura, é hospedeira de uma série de patógenos que podem limitar sua produção. A bactéria fastidiosa Leifsonia xyli subsp. xyli (Lxx) é o agente causal do raquistismo-das-soqueiras (RSD) em canade- açúcar cujo o principal sintoma é a redução acentuada do crescimento observada em plantas adultas. Essa doença é de difícil diagnose pois a evolução dos sintomas é lenta devido à natureza fastidiosa da bactéria. Lxx pode ser considerada como um endófíto obrigatório que cresce a níveis patogênicos nos tecidos da planta dependendo de estímulos bióticos e abióticos. Devido à importância da cultura e aos danosoCasionados pela Lxx, este trabalho apresentou dois enfoques principais: o primeiro foi o desenvolvimento de um protocolo para quantificação de Lxx em tecido de cana-de-açúcar por meio da técnica de PCR quantitativo em tempo real; o segundo foi o estudo da interação entre cana-de-açúcar e Lxx, em busca de uma melhor compreensão da evolução desse processo através da identificação de proteínas que apresentaram alteração em abundância ao longo do tempo em função da colonização pela bactéria em duas variedades de cana (RB835486 e SP80-3280) e em seguida enfatizando o sistema antioxidante nesta relação. Para isso, foram desenvolvidos primers específicos para detecção de Lxx que permitiram quantificar baixos níveis bacterianos em tecido foliar, revelando diferenças entre variedades segundo a cinética do crescimento bacteriano. Plantas com diferentes títulos bacterianos obtidas mediante inoculação artificial ou não foram submetidas à análise proteômica por meio da técnica de 2D-DIGE, uma vez que para o RSD, os danos estão relacionados à alta colonização de Lxx em seus tecidos. Os resultados alcançados com o sequenciamento de proteínas que apresentaram alteração em abundância revelaram que, em plantas da variedade RB835486 observou-se repressão de proteínas da via de estresse oxidativo e metabolismo primário, em contraste com a variedade SP80-3280, que apresentou aumento da abundância de proteínas relacionadas à via de estresse oxidativo, ambas para o mesmo tratamento, em plantas não inoculadas artificialmente. Já em plantas inoculadas com Lxx foram identificadas alteração na abundância de proteínas relacionadas ao crescimento da planta, ciclo celular, vias de sinalização celular e hormonal, esses resultados são consistentes com o principal sintoma da doença, o raquitismo, pois indica que as alterações temporais observadas na expressão de proteínas relacionadas com o aumento do título de Lxx in planta podem resultar em alterações do equilíbrio hormonal e menor crescimento da planta. Alguns resultados observados com a análise bioquímica corroboram com os dados acima descritos, pois a variedade RB835486 apresentou uma resposta precoce ao estresse oxidativo e mostrou maior controle do crescimento bacteriano, o que pode estar relacionado ao balanço de ERO\'s (espécies reativas de oxigênio) utilizadas pelo metabolismo como sinalizador celular na interação planta-patógeno. Em contraste, a variedade SP80-3280, em sua maioria, apresentou indução da atividade de enzimas antioxidantes mais tardiamente, momento em que a bactéria Lxx apresentou os maiores títulos de crescimento. / Sugarcane is currently the most grown crop in the state of São Paulo, with great importance in the agricultural sector. Like every crop, sugarcane is host to a number of pathogens that may limit its production. The fastidious bacterium Leifsonia xyli subsp. xyli (Lxx) is the causal agent of ratoon stunting in sugarcane (RSD), which the main symptom is a sharp reduction in growth observed in adult plants, this disease is difficult to diagnose because the evolution is slow due to nature of fastidious bacteria. Lxx can be considered as an obligatory endophyte that grows at pathogen levels in plant tissues depending on biotic and abiotic stimuli. Due to the importance of culture and the damage caused by the Lxx, this work presents two main approaches: the first one was the development of a protocol for the quantification of Lxx in sugarcane tissue by quantitative real time PCR; the second one was to study the interaction between sugarcane and Leifsonia xyli subsp. xyli aiming to a better understanding of the evolution of this process, identifying alterations in abundance of proteins over time depending on the bacterial colonization in the two varieties of sugarcane (RB835486 and SP80-3280) and then, emphasizing the antioxidant system in this relationship. Thus, we developed specific primers that enabled Lxx quantification at low bacterial levels in leaf tissue. The assay showed differences among sugarcane varieties according to the kinetics of bacterial growth. Plants that presented different titers of bacteria were obtained by artificial inoculum or not were selected to proteomic analysis by 2D-DIGE technique, since for RSD, the damage is related to high colonization in plant tissues. The identification of sugarcane proteins revealed that for variety RB835486 were observed a repression of stress proteins and proteins related to primary metabolism, in contrast with SP80-3280 variety, which it was identified high abundance of proteins of oxidative stress pathway, in not inoculated plants, for both varieties. However in inoculated plants it was identified a change in the abundance of proteins related to plant growth, cell cycle, cell signaling and hormonal pathways. These results corroborate with the main symptom of the disease, ratton, and suggest that temporal changes in expression of sugarcane cited proteins by increasing title of Lxx can result in hormonal imbalance and the decrease of plant growth. The major part of biochemistry analyzes corroborate with previous data obtained in proteomic approach. The RB835486 variety showed an early response to oxidative stress and suggests a greater control of bacterial growth in its tissues, which may be related to the balance of ERO\'s in signaling metabolism in plant pathogen interaction. While the SP80-3280, showed a later induction of antioxidant enzymes, when the bacterium Lxx had the highest titer of bacteria.

L’analyse microbiologique pour confirmer l’absence de bactéries dans des échantillons biologiques normalement sains, comme le sang, est une routine dans de nombreux laboratoires. En effet, la présence de bactéries dans le sang, appelée bactériémie, peut avoir des conséquences très graves, voire mortelles pour le patient. Le protocole standard pour la détection des bactériémies repose jusqu’ici sur l’enrichissement des échantillons sanguins prélevés sur les patients lors de l’hémoculture, afin d’obtenir une population suffisante pour analyse. La lenteur de ce procédé retarde ainsi de parfois plusieurs jours le diagnostic et donc l’adaptation du traitement antibiotique administré au patient. Ces dernières décennies, des techniques comme l’identification par spectrométrie de masse ou les analyses moléculaires, ont permis de diminuer le délai requis pour identifier les pathogènes en cause. Dans ce contexte, l’emploi de biocapteurs est également une alternative. Ce travail propose d’inclure des sondes à large spectre dans un capteur optique par imagerie SPR (résonance de plasmons de surface). Ce système est déjà développé pour la reconnaissance spécifique de pathogènes au cours de leur croissance dans le sang. Les nouveaux ligands proposés et évalués sont les peptides antimicrobiens (PAM). Ces courts peptides cationiques et amphiphiles, présentent l’avantage d’un large spectre d’interaction couplé à une haute stabilité (chimique, thermique et séchage) comparativement aux anticorps employés jusqu’ici. Leur immobilisation sur des prismes SPRI permet d’évaluer simultanément l’affinité de plusieurs PAM à la même souche bactérienne. Les biocapteurs ainsi préparés ont permis de détecter des souches pathogènes d’Escherichia coli et Staphylococcus aureus en milieu de culture simple, comme en plasma et en sang dilué au milieu d’hémoculture. Le système obtenu permet la détection des pathogènes présents à une concentration initiale de l’ordre de 1 UFC.ml-1, en moins de 24 heures et quel que soit le milieu. Enfin, la mise en place d’analyses statistiques multidimensionnelles a abouti à une classification cohérente des espèces ciblées en milieu simple, comme en sang. Ces résultats montrent le potentiel de ce système pour parvenir à développer un biocapteur à large spectre capable à la fois de détecter mais aussi d’identifier par affinité croisée des pathogènes bactériens. / Microbiological analysis to confirm the absence of bacteria in normally sterile biological samples, such as blood, is routine in many laboratories. The presence of bacteria in blood, called bacteremia, can have very serious, and even fatal consequences for the patient. So far, the standard protocol for their detection has been based on the enrichment of blood samples collected from patients, thanks to blood culture, in order to obtain a sufficient population for analysis. These procedures are time consuming which sometimes lead to delays in diagnosis and subsequent adaptation of antibiotic treatments by several days. In recent decades, techniques such as mass spectrometry identification or molecular analyses have reduced the time required to identify the pathogens involved. In this context, the use of biosensors is another promising alternative. This work proposes to include wide spectrum probes in an optical sensor using SPR imaging (surface plasmon resonance). This system is already developed for the specific recognition of pathogens during their growth in the blood. The new ligands we propose to evaluate are antimicrobial peptides (AMP). These short, cationic and amphiphilic peptides have the advantage of having a broad spectrum of interaction with bacteria, coupled with high stability (chemical, thermal and drying), especially compared to the antibodies used so far in this technique. Their immobilization on SPRI prisms allows the simultaneous evaluation of the affinity of several AMP to the same bacterial strain. The biosensors based on AMP were able to detect pathogenic strains of Escherichia coli and Staphylococcus aureus in simple culture medium, such as plasma and diluted blood in blood culture medium. The system obtained allows the detection of pathogens present at an initial concentration of about 1 CFU.ml-1, in less than 24 hours and in all assayed media. Finally, the implementation of multidimensional statistical analyses has resulted in a consistent classification of targeted species, in simple culture medium, such as blood. These results show the potential of this system to develop a wide-spectrum biosensor capable of both detecting and cross-referencing bacterial pathogens.