Transport of vitamin B12 in Escherichia coli: energy dependence

Abstract

This paper presents some evidence that the osmotic shock sensitive, energy dependent transfer of vitamin B12 from outer membrane receptor sites into the interior of cells of E. coli requires an energized inner membrane, without obligatory intermediation of adenosine 5' triphosphate (ATP). The experiments measured the effects of glucose D lactate, anaerobiosis, arsenate, cyanide, and 2,4 dinitrophenol upon the rates of B12 transport by starved cells of E. coli KBT001, which possesses a functional Ca2+, Mg2+ stimulated adenosine triphosphatase (Ca, Mg ATPase), and of E. coli AN120, which lacks this enzyme. Both strains were able to utilize glucose and D lactate aerobically to potentiate B12 transport, indicating that the Ca Mg ATPase was not essential for this process. When respiratory electron transport was blocked, either by cyanide or by anerobic conditions, and the primary source of energy for the cells was presumably ATP from glucose fermentation, the rate of B12 transport was much reduced in E. coli AN120 but not in E. coli KBT001.