damages membrane integrity and leads to blebbing of the
outer membrane, ultimately resulting in transient holes of
the gram-negative cell wall. This formation of holes
in the cell wall facilitates further AG uptake and appears to
significantly contribute to the bactericidal effect of AGs.
With this first step, AGs enter the periplasmic space of gramnegative
bacteria in a passive and non-energy-dependent
manner. In a second step (also referred to as energydependent
phase I), AGs are transported further through
the inner bacterial membrane in an oxygen-requiring process. Therefore, uptake is facilitated in aerobic bacteria [47].
Once in the cytosol, AGs interact with the 30S subunit
of bacterial ribosomes in a third and energydependent
step (energy-dependent phase II). At the
30S subunit, AGs bind to the decoding site located at the
A site of the 16S rRNA. Binding of AGs at this
site perturbs the recognition and selection of tRNA during
translation and increases misreading. Furthermore,
binding of AGs inhibits ribosomal translocation.
Perturbation of both ribosomal translation and translocation
ultimately inhibits protein synthesis. Interestingly, the
affinity for different rRNA binding sites varies amongst
different classes of AGs. This slightly different AGribosome
interaction, therefore, appears to be beneficial
against bacterial resistance