Biotin transport and accumulation by cells of Lactobacillus plantarum. I. General properties of the system.

Waller, James R. (University of Cincinnati, Cincinnati, Ohio), and Herman C. Lichstein. Biotin transport and accumulation by cells of Lactobacillus plantarum. I. General properties of the system. J. Bacteriol. 90:843-852. 1965.-Resting cells of Lactobacillus plantarum were saturated with bound biotin by incubation in phosphate buffer with biotin and glucose for 2 hr. This bound biotin was stable to wide changes in temperature, pH, and reaction time. Free biotin could be eluted from the cells by suspending them in cold water or saline. Immersing the cells in boiling water for 30 sec released all free biotin. Recoveries of added biotin exceeded 92%. Free biotin uptake by bound biotin-saturated cells occurred by two mechanisms. One process was independent from temperature (Q(10), 1.25), pH, cellular metabolism, and inhibition by iodoacetate. The other mechanism was dependent upon temperature (Q(10), 2.58; optimum, 37 C), pH (optimum, 7.5), and active cellular metabolism, and was inhibited by iodoacetate. Activation energies of 3,700 and 13,800 cal per mole, respectively, were observed for glucose-independent and -dependent free biotin uptake. Both processes exhibited approximately the same degree of inhibition by homobiotin. Higher concentrations of homobiotin were required to inhibit growth than to inhibit free biotin uptake. Intracellular-extracellular ratios as high as 600 were established in the absence of glucose, whereas ratios of nearly 4,000 occurred in the presence of glucose.