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Mangiano i metalli pesanti senza avvelenarsi e li digeriscono producendo oro: sono i batteri “re Mida”. Descritti sulla rivista Metallomics, vivono nel suolo e potrebbero essere preziosi in futuro per l'ambiente, come già avviene con un'eterogenea classe di microrganismi “green”: dai batteri mangia-petrolio o plastica a quelli antiruggine.
Denominati C. metallidurans, i ricercatori dell'Università tedesca Martin Lutero di Halle-Wittenberg, dell'Università Tecnica di Monaco e dell'Università australiana di Adelaide li hanno studiati per capire come e perché producano oro. Una delle ipotesi è che questo metallo faciliti la conversione del calcio, importante per il metabolismo del batterio ma tossico a elevate concentrazioni, in una forma più facile da utilizzare.
Per Dietrich H. Nies, uno degli autori, “in presenza dell'oro l'enzima con cui il batterio espelle il calcio è inattivato, consentendogli d'incamerarne una piccola quantità in una forma non tossica. L'oro in eccesso - ha concluso - è poi convertito in pepite delle dimensioni di pochi nanometri”.
ATS/Reuters/EnCa
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