Multimetal resistance and tolerance in microbial biofilms

How is it that biofilms are less susceptible to metal toxicity than exponentially growing planktonic cell populations? Here, Harrison and colleagues propose a multifactorial model of biofilm multimetal resistance and tolerance by which biofilms can withstand metal toxicity by an ongoing process of cellular diversification within the microbial population. Geochemical cycling and industrial pollution have made toxic metal ions a pervasive environmental pressure throughout the world. Biofilm formation is a strategy that microorganisms might use to survive a toxic flux in these inorganic compounds. Evidence in the literature suggests that biofilm populations are protected from toxic metals by the combined action of chemical, physical and physiological phenomena that are, in some instances, linked to phenotypic variation among the constituent biofilm cells. Here, we propose a multifactorial model by which biofilm populations can withstand metal toxicity by a process of cellular diversification.