title: Effect of osmotic shock and shearing forces on ferric enterochelin transport in Escherichia coli K12.
abstract: The fes mutation in Escherichia coli K12, which inactivates enterochelin esterase, allows the cell to accumulate ferric enterochelin. The ferric complex of enterochelin was released in significant quantities from a fes mutant after osmotic shock. Analysis of the effects of the individual stages of the shock procedure in wild-type cells showed that prior exposure of cells to sucrose and EDTA was not required, careful dilution of cells into a hypo-osmolar medium being sufficient to induce efflux of Fe3+. Prior treatment with EDTA or exposure to shearing forces served either to enhance efflux or to induce efflux in isotonic media. Neither vitamin B12 nor 5'-nucleotidase was released from the periplasm by these procedures. The release observed under mild conditions was stimulated specifically by Co2+, did not occur at 0 degree C, and was inhibited by 2,4-dinitrophenol at 37 degrees C. From these observations, it was concluded that the efflux of Fe3+ represents a physiological response of the cell to exposure to a hypo-osmolar medium. Such changes may enhance survival following physicochemical stressing of the bacterial outer membrane.
mesh_terms: D001692:Biological Transport; D002412:Cations / Q000378:metabolism; D004758:Enterobactin / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D007504:Iron Radioisotopes; D009997:Osmotic Pressure; D011865:Radioisotope Dilution Technique; D012694:Serine / Q000031:analogs & derivatives*
chemical_list: D002412:Cations; D007504:Iron Radioisotopes; D004758:Enterobactin; D012694:Serine; C014554:ferrienterochelin