FIG 7 .

Model of the metabolic compensation associated with overexpression of RND efflux pumps. RND efflux pumps are proton antiporters. Overexpression of these elements could result in the accumulation of protons in the cytoplasm with a concomitant deleterious intracellular acidification. To cope with this problem, P. aeruginosa could make use of the intracellular oxygen to get rid of excess protons. Nevertheless, this oxygen sequestration might decrease intracellular oxygen tension in such way that bacteria sense the situation as a switch to oxygen-limited conditions. As a consequence, the expression of typical pathways of the anaerobic metabolism, such as the nitrate respiratory chain, is triggered. (This figure was inspired by reference 48.)