Effect of bacterial inoculation, plant genotype and developmental stage on root-associated and endophytic bacterial communities in potato (Solanum tuberosum)

Beneficial bacteria interact with plants by colonizing the rhizosphere and roots followed by further spread through the inner tissues, resulting in endophytic colonization. The major factors contributing to these interactions are not always well understood for most bacterial and plant species. It is believed that specific bacterial functions are required for plant colonization, but also from the plant side specific features are needed, such as plant genotype (cultivar) and developmental stage. Via multivariate analysis we present a quantification of the roles of these components on the composition of root-associated and endophytic bacterial communities in potato plants, by weighing the effects of bacterial inoculation, plant genotype and developmental stage. Spontaneous rifampicin resistant mutants of two bacterial endophytes, Paenibacillus sp. strain E119 and Methylobacterium mesophilicum strain SR1.6/6, were introduced into potato plants of three different cultivars (Eersteling, Robijn and Karnico). Densities of both strains in, or attached to potato plants were measured by selective plating, while the effects of bacterial inoculation, plant genotype and developmental stage on the composition of bacterial, Alphaproteobacterial and Paenibacillus species were determined by PCR-denaturing gradient gel-electrophoresis (DGGE). Multivariate analyses revealed that the composition of bacterial communities was mainly driven by cultivar type and plant developmental stage, while Alphaproteobacterial and Paenibacillus communities were mainly influenced by bacterial inoculation. These results are important for better understanding the effects of bacterial inoculations to plants and their possible effects on the indigenous bacterial communities in relation with other plant factors such as genotype and growth stage

Cultivation of hitherto-uncultured bacteria belonging to the Verrucomicrobia subdivision 1 from the potato (Solanum tuberosum L.) rhizosphere

The role of dominant bacterial groups in the plant rhizosphere, e.g., those belonging to the phyla Acidobacteria and Verrucomicrobia, has, so far, not been elucidated, and this is mainly due to the lack of culturable representatives. This study aimed to isolate hitherto-uncultured bacteria from the potato rhizosphere by a combination of cultivation approaches. An agar medium low in carbon availability (oligotrophic agar medium) and either amended with potato root exudates or catalase or left unamended was used with the aim to improve the culturability of bacteria from the potato rhizosphere. The colony forming unit numbers based on colonies and microcolonies were compared with microscopically determined fluorescence-stained cell numbers. Taxonomical diversity of the colonies was compared with that of library clones made from rhizosphere DNA, on the basis of 16S rRNA gene comparisons. The oligotrophic media amended or not with catalase or rhizosphere extract recovered up to 33.6% of the total bacterial numbers, at least seven times more than the recovery observed on R2A. Four hitherto-uncultured Verrucomicrobia subdivision 1 representatives were recovered on agar, but representatives of this group were not found in the clone library. The use of oligotrophic medium and its modifications enabled the growth of colony numbers, exceeding those on classical agar media. Also, it led to the isolation of hitherto-uncultured bacteria from the potato rhizosphere. Further improvement in cultivation will certainly result in the recovery of other as-yet-unexplored bacteria from the rhizosphere, making these groups accessible for further investigation, e.g., with respect to their possible interactions with plants

Utilização de objetos de aprendizagem virtuais no ensino de ciências e matemática: proposta de formação continuada por meio das TIC

A utilização das TIC em sala de aula implica em reconhecimento da diversidade de recursos que se encontram disponibilizados na internet, porém, os professores ainda encontram muitas dificuldades em se apropriarem dessas possibilidades tecnológicas em suas ações didáticas. Ao se propor uma disciplina de mestrado em ensino de ciências e matemática envolvendo o uso de TIC, pôde-se estabelecer um caminho de discussão crítica com professores em formação continuada. Os alunos/ professores selecionaram e apresentaram objetos virtuais de aprendizagem nas discussões durante adisciplina e responderam um questionário investigativo sobre o uso dos objetos. Identificou-se que eles reconhecem a viabilidade pedagógica dos objetos trabalhados e que tais materiais influenciam de maneira efetiva a interação entre professores e alunos no processo de ensino aprendizagem

Ocorrência de Pantophthalmus kerteszianus Enderlein (Diptera: Brachycera) em Croton lanjowvensis (Euphorbiaceae) em Manaus, Estado do Amazonas

The fly Pantophthalmus kerteszianus Enderlein is reported for the first time attacking live tree trunks of Croton lanjowvensis Jablonski (dima) in Manaus city, Amazonas. During a year, five trees of this species were monitored. Adult flies were collected and measurements of diameter and depth of the holes as well as height of attack of larvae on the trunk were made. Seven adults were observed. The average diameter and depth of galleries in the transversal direction were 0.8 cm and 19.1 cm, respectively. The height of attack varied from 1 m to 3 m from the ground level

NN Scattering: Chiral Predictions for Asymptotic Observables

We assume that the nuclear potential for distances larger than 2.5 fm is given just by the exchanges of one and two pions and, for the latter, we adopt a model based on chiral symmetry and subthreshold pion-nucleon amplitudes, which contains no free parameters. The predictions produced by this model for nucleon-nucleon observables are calculated and shown to agree well with both experiment and those due to phenomenological potentials.Comment: 16 pages, 12 PS figures included, to appear in Physical Review

The rhizosphere selects for particular groups of acidobacteria and verrucomicrobia

There is a lack in our current understanding on the putative interactions of species of the phyla of Acidobacteria and Verrucomicrobia with plants. Moreover, progress in this area is seriously hampered by the recalcitrance of members of these phyla to grow as pure cultures. The purpose of this study was to investigate whether particular members of Acidobacteria and Verrucomicrobia are avid colonizers of the rhizosphere. Based on previous work, rhizosphere competence was demonstrated for the Verrucomicrobia subdivision 1 groups of Luteolibacter and Candidatus genus Rhizospheria and it was hypothesized that the rhizosphere is a common habitat for Acidobacteria subdivision 8 (class Holophagae). We assessed the population densities of Bacteria, Verrucomicrobia subdivision 1 groups Luteolibacter and Candidatus genus Rhizospheria and Acidobacteria subdivisions 1, 3, 4, 6 and Holophagae in bulk soil and in the rhizospheres of grass, potato and leek in the same field at different points in time using real-time quantitative PCR. Primers of all seven verrucomicrobial, acidobacterial and holophagal PCR systems were based on 16S rRNA gene sequences of cultivable representatives of the different groups. Luteolibacter, Candidatus genus Rhizospheria, subdivision 6 acidobacteria and Holophaga showed preferences for one or more rhizospheres. In particular, the Holophaga 16S rRNA gene number were more abundant in the leek rhizosphere than in bulk soil and the rhizospheres of grass and potato. Attraction to, and colonization of, leek roots by Holophagae strain CHC25 was further shown in an experimental microcosm set-up. In the light of this remarkable capacity, we propose to coin strain CHC25 Candidatus Porrumbacterium oxyphilus (class Holophagae, Phylum Acidobacteria), the first cultured representative with rhizosphere competenc

ANÁLISE DA ESTRATÉGIA ALIMENTAR DE MACRODON ANCYLODON (BLOCH & SCHNEIDER, 1801) - (PERCIFORMES: SCIAENIDAE) DE UM ESTUÁRIO DO LITORAL OCIDENTAL DO MARANHÃO - BRASIL

A dieta de Macrodon ancylodon (Bloch & Schneider, 1801) foi investigada analisando-se o conteúdo estomacal de 51 exemplares, com o comprimento padrão variando de 81-184mm, capturados por redes de espera e emalhe de deriva no estuário do rio Cocal, litoral ocidental do Maranhão, Brasil. A freqüência de ocorrência e a abundância das presas específicas foram utilizadas para descrever as estratégias alimentares empregadas pela espécie. O resultado apontou crustáceos decápodas e peixes como os itens mais abundantes da dieta. Conclui-se, que a espécie é carnívora generalista apresentando variações nas características morfológicas associadas com a alimentação e evidências de canibalismo.  ABSTRACT Analysis of feeding strategy of pescadinha-gó Macrodon ancylodon (Bloch & Schneider, 1801) - (Perciformes: Sciaenidae) from a estuary of the ocidental coast of Maranhão - Brazil The diet of Macrodon ancylodon (Bloch & Schneider, 1801) was investigated by analysis of the stomach contents of 51 specimes, with the standard length ranging from 81mm to 184mm. The specimes were captured by gill nets in the estuary of the Cocal river, Ocidental coast from Maranhão, Brazil. The occurrence frequency and the specific-preys abundance were used to describe the alimentary strategies employed by the species. The results pointed crustaceans decapods and fish as the most abundant itens of the diet. We concluded that M. ancylodon is carnivorous generalist, with variations in the morphological features associated with the feeding and it presents evidences of cannibalism.   Keywords: diet, Macrodon ancylodon, Maranhão, specialist, carnivorous, cannibalism

Classification of antimicrobial resistance using artificial neural networks and the relationship of 38 genes associated with the virulence of Escherichia coli isolates from broilers

Avian pathogenic Escherichia coli (APEC) is responsible for various pathological processes in birds and is considered as one of the principal causes of morbidity and mortality, associated with economic losses to the poultry industry. The objective of this study was to demonstrate that it is possible to predict antimicrobial resistance of 256 samples (APEC) using 38 different genes responsible for virulence factors, through a computer program of artificial neural networks (ANNs). A second target was to find the relationship between (PI) pathogenicity index and resistance to 14 antibiotics by statistical analysis. The results showed that the RNAs were able to make the correct classification of the behavior of APEC samples with a range from 74.22 to 98.44%, and make it possible to predict antimicrobial resistance. The statistical analysis to assess the relationship between the pathogenic index (PI) and resistance against 14 antibiotics showed that these variables are independent, i.e. peaks in PI can happen without changing the antimicrobial resistance, or the opposite, changing the antimicrobial resistance without a change in PI

The Two-Nucleon Potential from Chiral Lagrangians

Chiral symmetry is consistently implemented in the two-nucleon problem at low-energy through the general effective chiral lagrangian. The potential is obtained up to a certain order in chiral perturbation theory both in momentum and coordinate space. Results of a fit to scattering phase shifts and bound state data are presented, where satisfactory agreement is found for laboratory energies up to about 100 Mev.Comment: Postscript file; figures available by reques