The evolution of a superbug: how Staphylococcus aureus overcomes its unique susceptibility to polyamines.

Polyamines are ubiquitous compounds thought to be synthesized by and required for all life. The manuscript published in this issue by Joshi and colleagues upsets this dogma by identifying several bacterial species that do not make polyamines, and in some cases do not require polyamines for growth. One such species is the significant human pathogen Staphylococcus aureus, which is shown to be uniquely sensitive to polyamines. By unravelling the mechanisms of staphylococcal polyamine toxicity and tolerance, Joshi et al. (2011) provide insights into how the most virulent strains of S. aureus have evolved to be more fit during infection.