Copper resistance mechanisms in bacteria and fungi

Abstract

Copper is both an essential micronutrient and a toxic heavy metal for most living cells. The presence of high concentrations of cupric ions in the environment promotes the selection of microorganisms possessing genetic determinants for copper resistance. Several examples of chromosomal and plasmid copper-resistance systems in bacteria have been reported, and the mechanisms of resistance have started to be understood at the molecular level. Bacterial mechanisms of copper resistance are related to reduced copper transport, enhanced efflux of cupric ions, or copper complexation by cell components. Copper tolerance in fungi has also been ascribed to diverse mechanisms involving trapping of the metal by cell-wall components, altered uptake of copper, extracellular chelation or precipitation by secreted metabolites, and intracellular complexing by metallothioneins and phytochelatins; only the metallothionein chelation mechanism has been approached with molecular detail.

Tolerance and Bioaccumulation of Copper by the Entomopathogen Beauveria bassiana (Bals.-Criv.) Vuill. Exposed to Various Copper-Based Fungicides

“…This clearly indicates possession of copper tolerance mechanisms by this fungus strain. Copper tolerance of fungi has been ascribed to diverse mechanisms involving biosorption of the metal to cell surface, active uptake of copper, extracellular chelation or precipitation by secreted metabolites, and intracellular complexation (Cervantes and Gutierrez-Crona 1994). The copper tolerance displayed by our fungus strain could be related with the complexation of the mobilized toxic copper by chelating agents excreted by B. bassiana, such as protons and/or various metabolites (including organic acids), followed by their precipitation.…”

Production of laccase by a newly isolated deuteromycete fungus Pestalotiopsis sp. and its decolorization of azo dye

“…Copper is an essential micronutrient for most of living organisms [10], and copper requirements by microorganisms are usually satisWed in very low concentrations, ranging between 1 and 10 M. Copper present in higher concentrations in its free, cupric form, is extremely toxic to microbial cells [21]. In this paper, the optimal copper concentration for the laccase formation was found to be 2.0 mM.…”

“…This is only about 0.2% of the 2.0 mM added during the cultivation. Furthermore, fungi possess other, more eVective mechanisms of resistance against increased copper concentrations, such as intracellular complexing by metallothioneins and trapping of the metal by cell-wall components [10]. Apparently, the further investigation in such Weld associated with Pestalotiopsis sp.…”

GRISEA, a copper-modulated transcription factor from Podospora anserina involved in senescence and morphogenesis, is an ortholog of MAC1 in Saccharomyces cerevisiae

“…This is achieved at dierent levels, including the binding of extracellular copper to the cell wall or to secreted molecules, tight control of the transport of copper ions across the plasma membrane, and its chelation by cellular proteins ± the metallothioneins and phytochelatins (for reviews see: Cervantes and Gutierrez-Corona 1994;Zenk 1996). This complex molecular apparatus needs to be¯exible and able to react rapidly to changing copper concentrations.…”