The outer membrane of Pseudomonas aeruginosa is a barrier against the penetration of disaccharides

The outer membrane of Pseudomonas aeruginosa acted as a barrier against the penetration of di- (M_r, 342), tri- (M_r, 504) and tetrasaccharides (M_r, 666), whereas the membrane allowed the penetration of pentose (M_r, 150) and methylhexoses (M_r, 194) into the periplasm. When the intact cells of P. aeruginosa were treated with 600 mosM saccharides of various sizes and observed under an electron microscope, saccharides of M_r larger than 342 caused the extensive shrinking of the outer membrane. Whereas the cells treated with the saccharides of M_r less than 194 or with sucrose in the presence of EDTA showed plasmolysis. Determination of the extent of saccharide penetration into the periplasm of the cells treated with 600 mosM sodium chloride or with 600 mosM saccharides of various sizes showed that only pentose and hexoses, so far examined, were penetrable but di-, tri- and tetrasaccharides were impenetrable.