HEXITOL METABOLISM IN ESCHERICHIA COLI

Abstract

E. coli strain B grew rapidly on inorganic salts media containing glucose, galactose, mannose, fructose, mannitol, or sorbitol singly as sole C and energy source. Adaptation was seen with D-ribose and dulcitol. No growth occurred on L-sorbose, adonitol (ribitol), L-arabitol, or erythritol. Though D-mannitol 1-phosphate dehydrogenase is present in sonic extracts of cells grown on glucose, fructose, or dulcitol, growth on sorbitol produces a 4-fold increase in enzyme concentration, while extracts of cells grown on mannitol show a 10- to 15-fold rise in concentration of the enzyme. D-Sorbitol 6-phosphate is dehydrogenated in the presence of diphosphopy-ridine nucleotide by a sonic extract of sorbitol-grown cells, and not by extracts of cells grown on mannitol or dulcitol. Tagatose 6-phosphate is reduced in the presence of DPNH only by an extract of dulcitol-grown cells, and not by other extracts. The product of the reduction is presumably dulcitol 1-phosphate. Mannitol-grown E. coli will oxidize mannitol but not sorbitol, whereas sorbitol-grown cells will oxidize both hexitols. Kinases for the phosphorylation of hexitols probably exist; yeast hexo-kinase does not catalyze the phosphorylation of mannitol in the presence of adenosine triphosphate. The results are discussed in the light of Monod''s findings of induced enzyme synthesis in E. coli, and of observations by Edson and coworkers on the specificities of polyor dehydrogenases in general.