Data from: Social evolution of toxic metal bioremediation in Pseudomonas aeruginosa.

Bacteria are often iron-limited, and hence produce extracellular
iron-scavenging siderophores. A crucial feature of siderophore production
is that it can be an altruistic behaviour (individually costly but
benefitting neighbouring cells), thus siderophore producers can be invaded
by non-producing social ‘cheats’. Recent studies have shown that
siderophores can also bind other heavy metals (such as Cu and Zn), but in
this case siderophore chelation actually reduces metal uptake by bacteria.
These complexes reduce heavy metal toxicity, hence siderophore production
may contribute to toxic metal bioremediation. Here, we show that
siderophore production in the context of bioremediation is also an
altruistic trait and can be exploited by cheating phenotypes in the
opportunistic pathogen Pseudomonas aeruginosa. Specifically, we show that
in toxic copper concentrations (i) siderophore non-producers evolve de
novo and reach high frequencies, and (ii) producing strains are fitter
than isogenic non-producing strains in monoculture, and vice versa in
co-culture. Moreover, we show that the evolutionary effect copper has on
reducing siderophore production is greater than the reduction observed
under iron-limited conditions. We discuss the relevance of these results
to the evolution of siderophore production in natural communities and
heavy metal bioremediation.