Bacterial diversity in rhizosphere soil from Antarctic vascular plants of Admiralty Bay, maritime Antarctica

The Antarctic is a pristine environment that contributes to the maintenance of the global climate equilibrium. The harsh conditions of this habitat are fundamental to selecting those organisms able to survive in such an extreme habitat and able to support the relatively simple ecosystems. The DNA of the microbial community associated with the rhizospheres of Deschampsia antarctica Desv (Poaceae) and Colobanthus quitensis (Kunth) BartI (Caryophyllaceae), the only two native vascular plants that are found in Antarctic ecosystems, was evaluated using a 16S rRNA multiplex 454 pyrosequencing approach. This analysis revealed similar patterns of bacterial diversity between the two plant species from different locations, arguing against the hypothesis that there would be differences between the rhizosphere communities of different plants. Furthermore, the phylum distribution presented a peculiar pattern, with a bacterial community structure different from those reported of many other soils. Firmicutes was the most abundant phylum in almost all the analyzed samples, and there were high levels of anaerobic representatives. Also, some phyla that are dominant in most temperate and tropical soils, such as Acidobacteria, were rarely found in the analyzed samples. Analyzing all the sample libraries together, the predominant genera found were Bifidobacterium (phylum Actinobacteria), Arcobacter (phylum Proteobacteria) and Faecalibacterium (phylum Firmicutes). To the best of our knowledge, this is the first major bacterial sequencing effort of this kind of soil, and it revealed more than expected diversity within these rhizospheres of both maritime Antarctica vascular plants in Admiralty Bay, King George Island, which is part of the South Shetlands archipelago. The ISME Journal (2010) 4, 989-1001; doi:10.1038/ismej.2010.35; published online 1 April 2010

Biogeography of two cold-adapted genera: Psychrobacter and Exiguobacterium

The genera Exiguobacterium and Psychrobacter have been frequently detected in and isolated from polar permafrost and ice. These two genera have members that can grow at temperatures as low as -5 and -10 degrees C, respectively. We used quantitative PCR (Q-PCR) to quantify members of these genera in 54 soil or sediment samples from polar, temperate and tropical environments to determine to what extent they are selected by cold environments. These results were further analyzed by multiple linear regression to identify the most relevant environmental factors corresponding to their distribution. Exiguobacterium was detected in all three climatic zones at similar densities, but was patchier in the temperate and tropical samples. Psychrobacter was present in almost all polar samples, was at highest densities in Antarctica sediment samples, but was in very low densities and infrequently detected in temperate and tropical soils. Clone libraries, specific for the 16S rRNA gene for each genus, were constructed from a sample from each climatic region. The clone libraries were analyzed for alpha and beta diversities, as well as for variation in population structure by using analysis of molecular variance. Results confirm that both genera were found in all three climatic zones; however, Psychrobacter populations seemed to be much more diverse than Exiguobacterium in all three climatic zones. Furthermore, Psychrobacter populations from Antarctica are different from those in Michigan and Puerto Rico, which are similar to each other. The ISME Journal (2009) 3, 658-665; doi: 10.1038/ismej.2009.25; published online 26 March 2009

A magia desencantada: Henry James e o caso de "Os amigos dos amigos"

Por meio do exame do conto "Os amigos dos amigos" ("The friends of the friends"), de Henry James, bem como de seu processo de criação, este trabalho investiga a categoria do duplo confrontando as suas fontes primitivas com sua adoção na narrativa moderna - um confronto que nos permite sugerir uma chave de interpretação para a ficção jamesiana, e ainda discutir a presença do sobrenatural numa sociedade que privilegia o espetáculo, a publicidade, a novidade, o consumo e o progresso.

O modelo keynesiano de James Meade

Este artigo reavalia o "modelo simplificado" da Teoria Geral de Keynes elaborado por James Meade e procura complementar alguns dos argumentos teóricos que Meade deixou apenas indicados. O artigo também responde às solicitações de Frisch a Meade, quanto à explicação do significado de estabilidade e à explicitação dos pressupostos que garantem suas conclusões. Além disso, apresenta alguns dos cálculos não desenvolvidos por Meade, e, quando necessário, suas devidas correções.

Dynamics of cell and tissue genesis in the male reproductive system of ticks (Acari: Ixodidae) Amblyomma cajennense (Fabricius, 1787) and Amblyomma aureolatum (Pallas, 1772): a comparative analysis

Ticks are classified into three families: Argasidae, Ixodidae, and Nutalliellidae. The taxonomy and phylogeny within Ixodidae are still discussed by the specialists, thus requiring further studies. Amblyomma cajennese and Amblyomma aureolatum (Brazil) belong to two species complexes known as “cajennese” and “ovale”, respectively, and are directly related to the transmission of the Brazilian spotted fever. This confirms the medical and veterinary significance of these species, as well as the need for further morphological studies that will bring a better understanding of their taxonomy, phylogeny, and control. In this context, the present study aimed to characterize the morphology of the male reproductive system of A. cajennese and A. aureolatum when unfed and after 4 days of feeding, thereby seeking to: (a) distinguish the two species or “complexes”, and (b) study an internal system which has the potential to be targeted by acaricides. Therefore, males from both species (unfed and after 4 days of feeding) were cold-anesthetized, dissected, and had their reproductive systems removed for histological analysis. The results showed that the morphology of the male reproductive system is generally similar between both species, like in other Ixodidae ticks, exhibiting a multilobed accessory gland complex related to seminal fluid secretion, a pair of vasa deferentia and a pair of testes housing germ cells (spermatocytes) in different stages. The main differences were found in the development of the accessory gland complex cells and germ cells, showing that the maturation of the male reproductive system starts later in A. aureolatum, when compared to A. cajennese. However, during the blood meal, A. aureolatum development is increased, thus making germ cell maturation and gland complex activity higher than in A. cajennese. This study shows the differences in the development of the male reproductive systems of both species, while providing information that can assist in the establishment of new control methods.

Reassessment of the taxonomic status of Amblyomma cajennense (Fabricius, 1787) with the description of three new species, Amblyomma tonelliae n. sp., Amblyomma interandinum n. sp. and Amblyomma patinoi n. sp., and reinstatement of Amblyomma mixtum Koch, 1844, and Amblyomma sculptum Berlese, 1888 (Ixodida: Ixodidae)

A reassessment of the taxonomic status of Amblyomma cajennense based on the morphological analyses of ticks from the whole distribution area of the species resulted in the redescription of A. cajennense, the validation of 2 species which had been reduced to synonymy in the past, Amblyomma mixtum and Amblyomma sculptum, and the description and definition of 3 new species, Amblyomma tonelliae n. sp., Amblyomma interandinum n. sp., and Amblyomma patinoi n. sp. This study provides descriptions and redescriptions, scanning electron microscopic and stereomicroscopic images, updated synonymies, information on geographical distributions, and host associations for each of the 6 species. Amblyomma cajennense s.s. is found in the Amazonian region of South America, A. interandinum is reported from the northern part of the Inter-Andean valley of Peru, A. mixtum is present from Texas (U.S.A.) to western Ecuador, A. patinoi occurs in the Eastern Cordillera of Colombia, A. tonelliae is associated with the dry areas of the Chaco region which spans from central-northern Argentina to Bolivia and Paraguay, whereas A. sculptum is distributed from the humid areas of northern Argentina, to the contiguous regions of Bolivia and Paraguay and the coastal and central-western states of Brazil.