It is well appreciated that membrane permeability barriers are among the factors responsible for the intrinsic resistance of bacteria to antibiotics. The general diffusion porin OmpF (outer membrane protein F) of Escherichia coli is believed to be the principal pathway for the b -lactam antibiotics. To observe this channel-facilitated transport directly, we reconstituted purified OmpF into planar lipid membranes and studied its single channels in the presence of a b -lactam antibiotic, ampicillin. [PDF], (E.M. Nestorovich et al., Noise Analysis of Antibiotic Permeation through Bacterial Channels. In: First Intl. Conf. on Fluctuations and Noise in Biological, Biophysical, and Biomedical Systems, S.M. Bezrukov, H. Frauenfelder, F. Moss, eds., Proc. SPIE, vol. 5110, 2003, pp. 57-62. [PDF])

Is the interaction between effectively penetrating antibiotics and the outer membrane channel strong enough to render the passage events resolvable? Yes. Typical recordings of ion currents flowing through reconstituted OmpF trimers are shown in the figure.