Insecticidal features displayed by the beneficial rhizobacterium Pseudomonas chlororaphis PCL1606 / Características insecticidas mostradas por la rhizobacterium beneficiosa Pseudomonas chlororaphis PCL1606

The biocontrol rhizobacterium Pseudomonas chlororaphis is one of the bacterial species of the P. fluorescens group where insecticide fit genes have been found. Fit toxin, supported with other antimicrobial compounds, gives the bacterial the ability to repel and to fight against eukaryotic organisms, such as nematodes and insect larvae, thus protecting the plant host and itself. Pseudomonas chlororaphis PCL1606 is an antagonistic rhizobacterium isolated from avocado roots and show efficient biocontrol against fungal soil-borne disease. The main antimicrobial compound produced by P. chlororaphis PCL606 is 2-hexyl-5-propyl resorcinol (HPR), which plays a crucial role in effective biocontrol against fungal pathogens. Further analysis of the P. chlororaphis PCL1606 genome showed the presence of hydrogen cyanide (HCN), pyrrolnitrin (PRN), and homologous fit genes. To test the insecticidal activity and to determine the bases for such activity, single and double mutants on the biosynthetic genes of these four compounds were tested in a Galleria mellonella larval model using inoculation by injection. The results revealed that Fit toxin and HPR in combination are involved in the insecticide phenotype of P. chlororaphis PCL1606, and additional compounds such as HCN and PRN could be considered supporting compounds.(AU)

Impact of motility and chemotaxis features of the rhizobacterium Pseudomonas chlororaphis PCL1606 on its biocontrol of avocado white root rot

The biocontrol rhizobacterium Pseudomonas chlororaphis PCL1606 has the ability to protect avocado plants against white root rot produced by the phytopathogenic fungus Rosellinia necatrix. Moreover, PCL1606 displayed direct interactions with avocado roots and the pathogenic fungus. Thus, nonmotile (flgK mutant) and non-chemotactic (cheA mutant) derivatives of PCL1606 were constructed to emphasize the importance of motility and chemotaxis in the biological behaviour of PCL1606 during the biocontrol interaction. Plate chemotaxis assay showed that PCL1606 was attracted to the single compounds tested, such as glucose, glutamate, succinate, aspartate and malate, but no chemotaxis was observed to avocado or R. necatrix exudates. Using the more sensitive capillary assay, it was reported that smaller concentrations (1 mM) of single compounds elicited high chemotactic responses, and strong attraction was confirmed to avocado and R. necatrix exudates. Finally, biocontrol experiments revealed that the cheA and fglK derivative mutants reduced root protection against R. necatrix, suggesting an important role for these biological traits in biocontrol by P. chlororaphis PCL1606 (AU)

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Genes Involved in the Production of Antimetabolite Toxins by Pseudomonas syringae Pathovars.

Pseudomonas syringae is pathogenic in a wide variety of plants, causing diseases with economic impacts. Pseudomonas syringae pathovars produce several toxins that can function as virulence factors and contribute to disease symptoms. These virulence factors include antimetabolite toxins, such as tabtoxin, phaseolotoxin and mangotoxin, which target enzymes in the pathways of amino acid metabolism. The antimetabolite toxins are generally located in gene clusters present in the flexible genomes of specific strains. These gene clusters are typically present in blocks of genes that appear to be integrated into specific sites in the P. syringae core genome. A general overview of the genetic organization and biosynthetic and regulatory functions of these genetic traits of the antimetabolite toxins will be given in the present work.

Contribution of mangotoxin to the virulence and epiphytic fitness of Pseudomonas syringae pv. syringae

Mangotoxin is an antimetabolite toxin that inhibits ornithine acetyl transferase, a key enzyme in the biosynthetic pathway of ornithine and arginine and recently reported in strains of Pseudomonas syringae pv. syringae (Pss) isolated from mango. Since symptoms on mango tissues are very difficult to reproduce, in this study the role of mangotoxin in Pss virulence was addressed by analyzing the in planta growth and development of disease symptoms on tomato leaflets. Inoculation experiments were carried out following several procedures using the wild-type strain Pss UMAF0158, two Tn5-mutant derivative strains defective in mangotoxin production, and their complemented derivative strains in which mangotoxin production is restored. The ability of the mangotoxin-defective mutants to grow in planta was similar, and their epiphytic survival on the tomato leaf surface identical to the wild-type and complemented strains. However, both the disease index data of incidence and the severity of necrotic symptoms indicated that mangotoxin-defective mutants were less virulent, indicating that mangotoxin is a virulence factor. Furthermore, competition experiments showed that the survival values of the wild-type strain were slightly but significantly higher than those of the mangotoxin-defective mutants, suggesting that mangotoxin production would improve the epiphytic fitness of Pss (AU)

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Mechanisms of resistance to QoI fungicides in phytopathogenic fungi

The major threat to crops posed by fungal diseases results in the use by growers of enormous amounts of chemicals. Of these, quinol oxydation inhibitors (QoIs) are probably the most successful class of agricultural fungicides. QoIs inhibit mitochondrial respiration in fungi by binding to the Qo site of the cytochrome bc1 complex, blocking electron transfer and halting ATP synthesis. Unfortunately, the rapid development of resistance to these fungicides and consequent control failure has become increasingly problematic. The main mechanism conferring resistance to QoIs is target site modification, involving mutations in the cytochrome b gene CYTB, such as the substitution of glycine by alanine at position 143 (G143A) that occurs in several phytopathogenic fungi. The impact of other mechanisms, including alternative respiration and efflux transporters, on resistance seems to be limited. Interestingly, in some species QoI resistance is not supported by mutations in CYTB, while in others the structure of the gene is such that it is unlikely to undergo G143A mutations. Better understanding of the biological basis of QoI resistance in a single pathogen species will facilitate the development of resistance diagnostic tools as well as proper anti-resistance strategies aimed at maintaining the high efficacy of these fungicides (AU)

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Saneamento e saúde: malha hidrográfica da Leopoldina e impacto das doenças de veiculação hídrica no município do Rio de Janeiro / Sanitation and health: Leopoldina country hidrographic basin and study the impact of water-borne diseases in the city Rio de Janeiro

Esta pesquisa busca contribuir no aprofundamento da discussão do saneamento e saúde, utilizando como modelo a malha hidrográfica da Leopoldina e dar subsídios às políticas públicas do setor pelo impacto das doenças de veiculação hídrica observadas, reiteradamente, no Município do Rio de Janeiro. A utilização do saneamento como instrumento de promoção da saúde pressupõe a superação dos entraves tecnológicos, políticos e gerenciais que têm dificultado a extensão dos benefícios aos residentes em áreas rurais, municipais e localidades de pequeno porte. A maioria dos problemas sanitários que afetam a população mundial está relacionado com o meio ambiente. Um exemplo disso é a diarréia que, com mais de quatro bilhões de casos por ano, é a doenças que mais aflige a humanidade. Entre as causas dessas doenças destacam-se as condições inadequadas dos serviços de abastecimento de água e de esgotamento sanitário.

Alcoolismo: do conceito ao tratamento / Alcoholism: from concept to treatment

Faz-se uma retrospectiva das tentativas de tratamento de alcoólicos pelo Serviço de Psiquiatria e Psicologia Médica do Hospital do Servidor Público Estadual Francisco Morato de Oliveira, cujo modelo atual de assistência corresponde à rede de atendimento do alcoólico, constituída de quatro pólos integrados: 1. triagem; 2. internaçäo breve; 3. internaçäo prolongada; 4. psicoterapia em grupo. A psicoterapia em grupo representa o pólo axial do tratamento, havendo diferenças qualitativas entre os grupos em formaçäo e aqueles em andamento, nos quais os resultados da abordagem proposta säo característicos, expressando a resposta clínica favorável dos pacientes. Destaca-se a importância do modelo teórico adotado, o qual busca coerência sobre o diagnóstico e a intervençäo terapêutica, fornecendo as referências necessárias para a conduta médica

Alcoolismo: do conceito ao tratamento

Os autores fazem uma retrospectiva das tentativas de tratamento de alcoolicos pelo Servico Publico Estadual Francisco Morato de Oliveira, cujo modelo atual de assistencia corresponde a rede de atendimento do alcoolico, constituida de quatro polos integrados: 1. triagem; 2. internacao breve; 3. internacao prolongada; 4. psicoterapia em grupo. A psicoterapia em grupo representa o polo axial do tratamento, havendo diferencas qualitativas entre os grupos em formacao e aqueles em andamento, nos quais os resultados da abordagem proposta sao caracteristicos, expressando a resposta clinica favoravel dos pacientes. Destacam a importancia do modelo teorico adotado, o qual busca coerencia sobre o diagnostico e a intervencao terapeutica, fornecendo as referencias necessarias para a conduta medica.