Phosphotransferase Activity in \u3ci\u3eClostridium acetobutylicum\u3c/i\u3e from Acidogenic and Solventogenic Phases of Growth

Clostridium acetobutylicum cells, when energized with fructose, transported and phosphorylated the glucose analog 2-deoxyglucose by a phosphoenolpyruvate-dependent phosphotransferase (PT) system. Butanol up to 2% did not inhibit PT activity, although its chaotropic effect on the cell membrane caused cellular phosphoenolpyruvate and the 2-deoxyglucose-6-phosphate to leak out. Cells harvested from the solventogenic phase of batch growth had a significantly lower PT activity than did cells from the acidogenic phase

Betaine Transport Imparts Osmotolerance on a Strain of \u3ci\u3eLactobacillus acidophilus\u3c/i\u3e

Unlike most Lactobacilus acidophilus strains, a specific strain, L. acidophilus IF0 3532, was found to grow in rich medium containing 1 M sodium acetate, KCI, or NaCl. This strain could also grow with up to 1.8 M NaCl or 3 M nonelectrolytes (fructose, xylose, or sorbitol) added. Thus, this strain was tolerant to osmotic pressures up to 2.8 osM. A search for an intracellular solute which conferred osmoprotection led to the identification of glycine betaine (betaine). Betaine was accumulated to high concentrations in cells growing in MRS medium supplemented with 1 M KCI or NaCl. Uptake of [14C]betaine by L. acidophilus 3532 cells suspended in buffer was stimulated by increasing the medium osmotic pressure with 1 M KCI or NaCl. The accumulated betaine was not metabolized further; transport was relatively specific for betaine and was dependent on an energy source. Other lactobacilli, more osmosensitive than strain 3532, including L. acidophilus strain E4356, L. bulgaricus 8144, and L. delbrueckii 9649, showed lower betaine transport rates in response to an osmotic challenge than L. acidophilus 3532. Experiments with chloramphenicol-treated L. acidophilus 3532 cells indicated that the transport system was not induced but appeared to be activated by an increase in osmotic pressure