Paracoccidioides brasiliensis is a thermodimorphic fungus associated with paracoccidioidomycosis (PCM), a systemic mycosis prevalent in South America. In humans, infection starts by inhalation of fungal propagules, which reach the pulmonary epithelium and transform into the yeast parasitic form. Thus, the mycelium-toyeast transition is of particular interest because conversion to yeast is essential for infection. We have used a P. brasiliensis biochip carrying sequences of 4,692 genes from this fungus to monitor gene expression at several time points of the mycelium-to-yeast morphological shift (from 5 to 120 h). The results revealed a total of 2,583 genes that displayed statistically significant modulation in at least one experimental time point. Among the identified gene homologues, some encoded enzymes involved in amino acid catabolism, signal transduction, protein synthesis, cell wall metabolism, genome structure, oxidative stress response, growth control, and development. The expression pattern of 20 genes was independently verified by real-time reverse transcription-PCR, revealing a high degree of correlation between the data obtained with the two methodologies. One gene, encoding 4-hydroxyl-phenyl pyruvate dioxygenase (4-HPPD), was highly overexpressed during the myceliumto-yeast differentiation, and the use of NTBC [2-(2-nitro-4-trifluoromethylbenzoyl)-cyclohexane-1,3-dione], a specific inhibitor of 4-HPPD activity, as well as that of NTBC derivatives, was able to inhibit growth and differentiation of the pathogenic yeast phase of the fungus in vitro. These data set the stage for further studies involving NTBC and its derivatives as new chemotherapeutic agents against PCM and confirm the potential of array-based approaches to identify new targets for the development of alternative treatments against pathogenic microorganisms.
Genetically distinct strains of the plant bacterium Xylella fastidiosa (Xf) are responsible for a variety of plant diseases, accounting for severe economic damage throughout the world. Using as a reference the genome of Xf 9a5c strain, associated with citrus variegated chlorosis (CVC), we developed a microarray-based comparison involving 12 Xf isolates, providing a thorough assessment of the variation in genomic composition across the group. Our results demonstrate that Xf displays one of the largest flexible gene pools characterized to date, with several horizontally acquired elements, such as prophages, plasmids, and genomic islands (GIs), which contribute up to 18% of the final genome. Transcriptome analysis of bacteria grown under different conditions shows that most of these elements are transcriptionally active, and their expression can be influenced in a coordinated manner by environmental stimuli. Finally, evaluation of the genetic composition of these laterally transferred elements identified differences that may help to explain the adaptability of Xf strains to infect such a wide range of plant species
O presente trabalho incorpora resultados de uma pesquisa realizada no doutorado, que examina, numa perspectiva sócio-histórico-comparada, manuais pedagógicos publicados em Portugal e no Brasil entre 1870 e 1970. O corpus é composto por 80 títulos sobre didática, pedagogia, metodologia e prática de ensino, dos quais 25 são portugueses e 55 são brasileiros. Esses livros resumiram a bibliografia educacional e explicaram aos futuros professores os vários elementos da cultura escolar, difundida em diferentes partes do mundo. O intuito é comparar referências mencionadas nas páginas dos manuais para compreender como elas foram usadas na construção das concepções sobre o magistério e conhecer, assim, modalidades de circulação e apropriação de conhecimentos produzidos em diversos lugares, épocas e áreas de saber. A história dos manuais pedagógicos aqui proposta enfatiza, portanto, os modos pelos quais esses livros colaboraram com a difusão de um modelo de escola que hoje é conhecido mundialmente.
Background: The xylem-inhabiting bacterium Xylella fastidiosa (Xf) is the causal agent of Pierce's disease (PD) in vineyards and citrus variegated chlorosis (CVC) in orange trees. Both of these economically-devastating diseases are caused by distinct strains of this complex group of microorganisms, which has motivated researchers to conduct extensive genomic sequencing projects with Xf strains. This sequence information, along with other molecular tools, have been used to estimate the evolutionary history of the group and provide clues to understand the capacity of Xf to infect different hosts, causing a variety of symptoms. Nonetheless, although significant amounts of information have been generated from Xf strains, a large proportion of these efforts has concentrated on the study of North American strains, limiting our understanding about the genomic composition of South American strains -which is particularly important for CVC-associated strains.
The main control strategy for Ascaris lumbricoides is mass drug administration (especially with benzimidazoles), which can select strains of parasites resistant to treatment. Mutations in the beta-tubulin isotype-1 gene at codons 167, 198 and 200 have been linked to benzimidazole resistance in several nematodes. The mutation in codon 200 is the most frequent in different species of parasites, as previously observed in Necator americanus and Trichuris trichiura; however, this mutation has never been found in populations of A. lumbricoides. This study aimed to screen for single nucleotide polymorphisms (SNPs) in the beta-tubulin isotype-1 gene at codon 200 in A. lumbricoides. We developed a technique based on an amplification refractory mutation system (ARMS-PCR) for the analysis of 854 single A. lumbricoides eggs collected from 68 human stool samples from seven Brazilian states. We detected the mutation in codon 200 at a frequency of 0.5% (4/854). This is the first report of this mutation in A. lumbricoides. Although the observed frequency is low, its presence indicates that these parasite populations have the potential to develop high levels of resistance in the future. The methodology proposed here provides a powerful tool to screen for the emergence of anthelmintic resistance mutations in parasitic nematode populations.
Hookworms are intestinal parasites that cause major public health problems, especially in developing countries. To differentiate eggs from different hookworm species, it is necessary to use molecular methodologies, since the eggs are morphologically similar. Here, we performed the molecular identification of single hookworm eggs from six Brazilian states. Of the 634 eggs individually analyzed, 98.1% (622/634) represented Necator americanus, and surprisingly, 1.9% (12/634 eggs from the same patient) represented Ancylostoma caninum. DnA analysis of the A. caninum-positive stool sample revealed no contamination with animal feces. This is the first report of the presence of A. caninum eggs in human feces, which may have a direct implication for the epidemiology of hookworm infection caused by this species. This suggests the need for special attention regarding prophylaxis, as different reservoirs, previously not described, may have great relevance for the spread of A. caninum.
The objective of this study was to evaluate the effects of cover crops grown under no-tillage on the aggregation and physical protection of organic matter in soil macro and microaggregates. The experiment consisted of a randomized complete block design with three replications. The following cover crops were investigated in corn rotation systems: T1 = Braquiária ruziziensis (Urochloa ruziziensis), T2 = Canavalia brasiliensis Mart. ex Benth.,Br.], T5 = turnip-forage (Raphanus sativus L.), T6 = velvet bean (Mucuna aterrima Merr.) and T7 = native Cerrado vegetation as a reference environment. Soil was sampled at a depth of 0-10 cm in September 2015 for the determination of organic matter fractions in macro and microaggregates. There was a reduction in aggregate size and its stability when native Cerrado areas were converted into agricultural systems. Nevertheless, some cover crops such as velvet bean, millet and turnip-forage favored restructuring the soil, forming stable aggregates similar to the native Cerrado. Among the cover crops, millet was highlighted as presenting elevated capacity to accumulate labile organic carbon in macroaggregates (2.32 g C kg -1 ) and microaggregates (2.34 g C kg -1 ). These values are, on average, 60% higher than those presented by turnip-forage. In general, the conversion of land use under Cerrado vegetation to agroecosystems reduced the total organic carbon content, mainly due to macroaggregate breakup, resulting in a lower physical protection of soil organic matter.
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