Intracellular mannitol, a product of glucose metabolism in staphylococci

Abstract

Mannitol (Mtl), not previously reported as an intracellular component of bacteria, although it has been found as an extracellular end product of anaerobic carbohydrate metabolism, accumulated within strains of all 10 staphylococcal species tested after aerobic incubation of washed cell suspensions in phosphate-buffered 1% glucose for 2 h. Phenol extracts of the cells, before and after incubation, were analyzed for Mtl content by periodate utilization and paper chromatography and for Mtl 1-phosphate content, with Mtl 1-phosphate dehydrogenase. In Staphylococcus aureus Towler, the content of Mtl increased from a 0-h value of less than 2.4 to 16 mumol/g (dry weight) after incubation, and the level of Mtl 1-phosphate increased from a 0-h value of 1 to 8 mumol/g. The identification of Mtl was confirmed as the per-O-acetyl ester by gas-liquid chromatography and as the per-O-methyl ether by mass spectrometry. Also tested were 5 additional S. aureus strains and 32 coagulase-negative staphylococcal strains. All strains accumulated Mtl, even those strains that could not utilize exogenous Mtl during aerobic growth, usually in the range 4 to 25 mumol/g. Furthermore, three strains accumulated very high Mtl levels. Bacteria from several other genera were tested, and some were found to accumulate low to moderate levels of Mtl under similar incubation conditions. The metabolic conversion of glucose to intracellular Mtl, probably via Mtl 1-phosphate, is a common feature of staphylococci and also occurs in some other bacteria.