Perchlorate and chlorate reduction by the Crenarchaeon Aeropyrum pernix and two thermophilic Firmicutes

This study reports the ability of one hyperthermophile and two thermophilic microorganisms to grow anaerobically by the reduction of chlorate and perchlorate. Physiological, genomic and proteome analyses suggest that the Crenarchaeon Aeropyrum pernix reduces perchlorate with a periplasmic enzyme related to nitrate reductases, but that it lacks a functional chlorite-disproportionating enzyme (Cld) to complete the pathway. A. pernix, previously described as a strictly aerobic microorganism, seems to rely on the chemical reactivity of reduced sulfur compounds with chlorite, a mechanism previously reported for perchlorate-reducing Archaeoglobus fulgidus. The chemical oxidation of thiosulfate (in excessive amounts present in the medium) and the reduction of chlorite result in the release of sulfate and chloride, which are the products of a biotic-abiotic perchlorate reduction pathway in A. pernix. The apparent absence of Cld in two other perchlorate-reducing microorganisms, Carboxydothermus hydrogenoformans and Moorella glycerini strain NMP, and their dependence on sulfide for perchlorate reduction is consistent with observations made on A. fulgidus. Our findings suggest that microbial perchlorate reduction at high temperature differs notably from the physiology of perchlorate- and chlorate-reducing mesophiles and that it is characterized by the lack of a chlorite dismutase and is enabled by a combination of biotic and abiotic reactions.

The trading relationship between the EU and Mercosur: the mediatory role of Brazil

Dissertação de mestrado em European and Transglobal Business Law

Metáforas da crise cotidiana: os media e a veiculação da crise grega

A partir da forma como nos media portugueses são veiculadas as relações de oposição e negociação entre a Grécia e a União Europeia, pode verificar-se a importância e a força que a metáfora conceitual possui como mecanismo linguístico e cognitivo de construção de perceções, defesa de pontos de vista e fundamento de perspectivas ideológicas. Alicerçando-se numa estrutura metafórica de base, a negociação é colocada entre os domínios JOGO e LUTA, evidenciando-se o peso das metáforas como poderosos mecanismos para construir e manipular as perceções que temos sobre a realidade.

Migrações recentes de portugueses para Angola: contextos e estratégias

Dissertação de mestrado em Sociologia das Organizações e Trabalho

Potencial geopolítico da língua portuguesa para Timor-Leste

Dissertação de mestrado em Relações Internacionais