J. Bjorkman et al., Effects of environment on compensatory mutations to ameliorate costs of antibiotic resistance, SCIENCE, 287(5457), 2000, pp. 1479-1482
Most types of antibiotic resistance impose a biological cost on bacterial f
itness. These costs can be compensated, usually without Loss of resistance,
by second-site mutations during the evolution of the resistant bacteria in
an experimental host or in a Laboratory medium. Different fitness-compensa
ting mutations were selected depending on whether the bacteria evolved thro
ugh serial passage in mice or in a Laboratory medium. This difference in mu
tation spectra was caused by either a growth condition-specific formation o
r selection of the compensated mutants. These results suggest that bacteria
l evolution to reduce the costs of antibiotic resistance can take different
trajectories within and outside a host.