In Shigella strains were studied the molecular mechanism that mediated the multiply antibiotic-resistance. Twenty-six strains of Shigella flexneri were utilised in this investigation. These strains were submitted to disk diffusion test, mating experiments and plasmid isolation. In relation to antibiotics resistance standard it was observed that all Shigella flexneri strains were resistant to at least, three antibiotics tested. From twenty-six Shigella flexneri strains donors submitted to conjugation process, 34.6% (nine strains) resulted in variable frequency of transconjugants. From strains that conjugated, 100%, transferred the resistance factor acquainted with ampicillin. Being that, in all transconjugants which were observed, just one plasmid with 23.1 Kb was evidenced. This plasmid found in all strains was characterised as the cause of resistance to ampicillin.

Continental shelves with diversified physiography, geomorphology marked by rocky reefs, channels, and marginal terraces, besides several terrestrial and marine sediments, have a rich mosaic of habitats ideal for the conservation and reproduction of marine life. This work, as part of the research project "Detailed Study of the Ocean Bed inside the Santa Cruz WLR, Costa das Algas EPA and 2000m Immediate Environment", aims at mapping the marine habitats located in two Conservation Units, Costa das Algas EPA (Environmental Protection Area) and Santa Cruz WLR (Wildlife Refuge), located south of the Doce River mouth, on the southeast coast of Brazil. For this purpose, data on the type, distribution, and composition of seabed sediments, as well as information on the seabed geomorphology using bathymetric data, seabed records by ROV imaging, and benthic fauna at the phylum taxonomic level were determined in the studied areas. The results indicated the presence of five sedimentary facies defined by the terrigenous and marine sedimentation regimes, separated in the vicinity of the-35 m isobath. The sandy-clayey sediments deposited by the fluvial discharges from the region rivers predominate in the first case. On the other hand, the marine sedimentation consists of biolitoclastic and bioclastic sediments, with rhodolith pebbles as well. In addition, three hydrodynamic zones/regions were defined, according to the presence and type of seabed ripples formed by near-bottom waves. The bathymetric data revealed seabed features such as reef structures, or rocky reefs, as well as submerged channels originated by marine regression. This set of characteristics defined eleven marine habitats, and among them, those consisting of biolitoclastic, bioclastic and rhodolith sediments, as well as rocky reefs and submerged channels, which had the greatest abundance of marine fauna and flora organisms. On the other hand, the habitats defined by the terrigenous sedimentation had a lower abundance of organisms. This finding indicates that the marine sedimentation regime predominated over the terrigenous, especially in the Costa das Algas EPA, which generally represents an area with high potential for proliferation and preservation of marine benthic and demersal fauna and flora. In view of this, the mapping of the Conservation Units presented here for the first time on a detailed scale can help to understand the importance of these areas for the preservation and maintenance of marine life.

Abstract:The São Miguel do Tapuio Circular Structure (SMTCS) is one of the largest recognized in the Phanerozoic sedimentary rocks of the Parnaiba Basin, in Piauí (PI), Brazil. Research works on the genesis of the SMTCS consider either an endogenetic origin or meteoritic impact formation. The present study is based on bibliographic survey, fi eldwork and laboratory analyses (remote sensing). The SMTCS superfi cial morphological features, their organization, total diameter, multi-directional pattern and high density of lineaments inside the structure were characterized by remote sensing. Also, the morphostructural units such as the outer margin, intermediate ring, annular depression and a central topographic high were defi ned. The fi eldwork allowed identifying a variable thermal metamorphism in the Keywords:Bacia do Parnaíba; Astroblemas; Sensoriamento Remoto. 764Martins J. A. et al. Rev. Bras. Geomorfol. (Online), São Paulo, v.17, n.4, (Out-Dez) p.763-781, 2016 sandstones that formed the SMTCS. The metamorphism grade increased clearly from the margin to the center, with the presence of highly recrystallized and consolidated metasandstones around the center of the structure. Finally, the geomorphic characterization and the geometric signature obtained for the SMTCS seem to correspond to those of complex impact structures (presence of a central uplift). Moreover, the identifi cation of macro and microscopic deformation structures in the sandstones (while not typical of shock origin) may be more conclusive of a meteoritic origin, and the lack of evidence of igneous activity might explain the observed thermal metamorphism. Resumo:A estrutura circular de São Miguel do Tapuio (ECSMT) corresponde a uma das maiores do gênero registrada em rochas sedimentares fanerozoicas da Bacia do Parnaíba, Estado do Piauí, Brasil. As pesquisas considerando a gênese da ECSMT dividem-se entre uma origem endógena e uma através de impacto meteorítico. No presente estudo foram realizados trabalhos envolvendo o estágio do conhecimento atual, campo e laboratoriais (sensoriamento remoto). Os trabalhos de sensoriamento serviram para delinear a confi guração morfológica superfi cial, o diâmetro total e compartimentos, bem como o padrão multidirecional e alta densidade dos lineamentos no interior da estrutura. Puderam ser defi nidas unidades morfoestruturais como a borda externa, o anel intermediário, a depressão anelar e um alto topográfi co central. Os trabalhos de campo evidenciaram uma intensidade de metamorfi smo termal variável observado nos arenitos interiores à ECSMT. Da borda para o centro observa-se nítido aumento no grau de metamorfi smo nos arenitos, caracterizando metarenitos intensamente recristalizados e consolidados no entorno do centro da estrutura. Finalizando, a caracterização morfológica superfi cial e a assinatura geométrica obtida para a ECSMT são semelhantes e condizentes com várias estruturas de impacto do tipo complexa (presença de um núcleo soerguido). Somado a estes fatos temos a presença de estruturas deformaci...

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