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Programa de Pós-Graduação em Biotecnologia. Núcleo de Pesquisas em Ciências Biológicas, Pró-Reitoria de Pesquisa de Pós Graduação, Universidade Federal de Ouro Preto. A agricultura é um dos principais setores da economia brasileira com uma expressiva influência no crescimento do PIB brasileiro. Uma das commodities que mais contribui para este fato é a citricultura, uma vez que o Brasil ocupa o papel de maior produtor e exportador de citros do mundo. Entretanto, diversos fatores têm afetado a produtividade de citros, com destaque para os problemas fitossanitários que acometem essa atividade em todo país. Caracterizadas pela sua fácil disseminação, três espécies de Xanthomonas estão associadas com a geração de danos e consequentes perdas citrícolas: X. citri subsp. citri patotipo A (XccA), agente causal do Cancro Cítrico Asiático, X. fuscans subsp. aurantifolii variante B (XauB) e C (XauC) causadoras da Falsa Cancrose e da Cancrose C, respectivamente, e X. alfalfae subsp. citrumelonis (Xacm) causadora da Mancha Bacteriana dos Citros. Estes diferem quanto à virulência, patogenicidade e hospedeiros. Dessa forma, estudos que visem o desenvolvimento de tecnologias para a detecção, identificação e controle dessas diferentes espécies são de extrema importância. Assim, o objetivo desse estudo foi desenvolver um método de diagnóstico molecular a partir de sequências únicas identificadas por genômica comparativa que permitam a discriminação individual e múltipla das diferentes variantes de Xanthomonas que infectam Citrus. Para a identificação das sequências únicas, análises de ferramentas OrthoMCL, MAUVE, Primer Designing do NCBI e PCR in silico foram utilizadas para o desenho e validação inicial, considerando as diferenças nos tamanhos dos amplicons de modo a facilitar a análise visual do produto amplificado. As regiões alvo foram amplificadas por PCR e analisadas em gel de agarose 3%. Os resultados mostraram que os marcadores moleculares foram específicos aos genomas alvo in silico, in vitro e in vivo, sem qualquer amplificação cruzada nos outros genomas de referência, o que foi reiterado pelos resultados de PCR multiplex. A sensibilidade de detecção foi de até 0,02ng/μL nos testes in vitro e até 1,5 x 104 UFC mL-1 nos teste in vivo. Todos os resultados encontrados não apenas evidenciaram a possibilidade de diagnóstico por diferenciação das distintas variantes de Xanthomonas causadora de doenças em citros por meio de PCR como validaram a ferramenta computacional desenvolvida para este fim. Agriculture is one of the main sectors of the Brazilian economy with a significant influence in the growth of the Brazilian GDP. One of the commodities that contributes most to this fact is citriculture, whereas Brazil occupies the largest citrus producer and exporter in the world. However, several factors have affected citrus productivity, with emphasis on phytosanitary problems that affect this activity throughout country. Three species of Xanthomonas are associated with the generation of damages and consequent citrus losses: X. citri subsp. citri pathotype A (XccA), causative agent of Asian Citrus Cancer, X. fuscans subsp. aurantifolii pathotype B (XauB) and C (XauC) causative of False Citrus Canker and Cancrose C, respectively, and X. alfalfae subsp. citrumelonis (Xacm) causing Citrus Bacterial Spot disease. These species differ in virulence, pathogenicity and host. Therefore, studies aimed at the development of technologies for the detection, identification, and control of these different species are extremely important. Thus, the aim of this study was to develop a molecular diagnostic method from unique sequences identified by comparative genomics that allow the individual and multiple discrimination of the different Xanthomonas variants that infect Citrus. For the identification of unique sequences, analyzes of OrthoMCL, MAUVE, Primer Designing of the NCBI and PCR in silico were used for the design and initial validation, considering the differences in the sizes of the amplicons in order to facilitate the visual analysis of the amplified product. The target regions were amplified by PCR and analyzed on 3% agarose gel. The results showed that the molecular markers were specific to the target genomes in silico, in vitro, and in vivo without any cross-amplification in the other reference genomes, which was reiterated by multiplex PCR results. The detection sensitivity was up from to 0.02ng/μL in the in vitro tests and up to 1.5 x 104 UFC mL-1 in vivo assays. All the results not only highlighted the first empirical diagnostic tool for different variants of Xanthomonas that causes disease in citrus, but also validated the computational tool developed for this purpose.

The ferruginous rupestrian grasslands (FRG) in the Iron Quadrangle (IQ) are ecosystems characterized by rocky soils with reduced availability of water and nutrients, but high levels of metals. In order to comprehend the interference of microorganisms on the adaptive process of endemic plant Mimosa calodendrum (Fabaceae), bacteria associated with its roots and rhizosphere were isolated. Fourteen isolates were obtained and subsequently grown in the presence of different concentrations of arsenic (As) species. The isolate Mc250, an Alcaligenes faecalis strain, resisted to 10 mM of As (III) and 800 mM of As (V). In the presence of this strain, atomic spectrometer detected a reduction of 55% for As (III) and 72% for As (V) respectively in 10 mM and 500 mM solution. Scanning electron microscopy of this isolate demonstrated morphological modification and EDX spectroscopy revealed the presence of both As species adsorbed on the membrane, justifying the removal observed in the in vitro assays. To validate this potential removal of As in vivo, tomato plants were used as grown model in the presence and absence of A. faecalis in soil previously contaminated with 5 mM of As (III). After 14 days, plants from contaminated soil had their growth improved when compared to untreated control plants. All these results suggest for the first time that plant-associated bacteria from FRG-IQ present potential for soil rhizoremediation and may benefit the adaptive processes of plants in extreme environments including application in recovering degraded areas.