Virtually all biological material has some affinity for toxic metals (Gadd and White 1993) and several mechanisms by which metals interact with microbial cell walls and envelopes are well established (Beveridge et al. 1997; Lovley et al. 1991). However some biomolecules function specifically to bind metals and are even genetically induced by their presence (Macaskie and Dean 1990). In S. cerevisiae the low molecular weight cysteine-rich polypeptide metalothionein binds Cu+2 and Zn+2 as well as Zn+2 and provides resistance through detoxification of metal ions encountered in the natural environment (Turner and Robinson 1995).
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