Choline transport activity in Staphylococcus aureus induced by osmotic stress and low phosphate concentrations

Abstract

Uptake of [14C]choline upon hyperosmotic stress of exponential-phase Staphylococcus aureus cultures in a complex medium occurred after a delay of 2.5 to 3.5 h. This uptake could be prevented by chloramphenicol, suggesting that it occurred via an inducible transport system. Radioactivity from ['4Clcholine was accumulated as [14Clglycine betaine. However, neither choline nor glycine betaine could act as the major carbon and energy source for the organism, suggesting that choline was not metabolized beyond glycine betaine. Assay of choline transport activity in cells grown under different conditions in defined media revealed that osmotic stress was mainly responsible for the induction, but choline gave a further increase in induction. The system was not induced in anaerobically grown cells. Choline transport activity was repressed by glycine betaine and proline betaine, suggesting that these compounds are corepressors. Choline transport activity was not induced in cells osmotically stressed by 1 M potassium phosphate or 0.5 M sodium phosphate, but was induced in cells grown in low-phosphate medium in the absence of osmotic stress. This suggests that there is a connection between the phosphate and osmotic stress regulons. Choline transport was energy and Na' dependent and had a Km of 46 FLM and a maximum rate of transport (Vmax) of 54 nmol/min/mg (dry weight). The results of competition studies suggested that N-methyl and an alcohol group or aldehyde groups at the ends of the molecule were important in its recognition by the system. Glycine betaine was not a highly effective competitor, suggesting that its transport system and the choline transport system were distinct from each other. Choline transport was highly susceptible to a variety of inhibitors, which may be related to the greater dependence on respiratory metabolism of cells grown in the presence of high NaCl concentrations.

Osmoregulation in Bacillus subtilis: synthesis of the osmoprotectant glycine betaine from exogenously provided choline

“…6B and C). Thus, B. subtilis uses exoge- 4,7,8,17,22,23,29). This oxidation is a two-step process with e as a precursor for glycine betaine synthesis.…”

“…to (17,27,28), the fully methylated quaternary ammonium group is a key feature for substrate recognition (Table 1). Exogenously provided glycine betaine aldehyde is an effective inhibitor for choline uptake (Table 1) and also functions as a potent osmoprotectant in B. subtilis (Fig.…”

Increased cell size and shortened peptidoglycan interpeptide bridge of NaCl-stressed Staphylococcus aureus and their reversal by glycine betaine

“…The alteration in the peptidoglycan composition caused by adding glycine betaine to cells growing in the presence of 2.5 M NaCl may be an indirect effect, a result of more global effects of glycine betaine, such as increasing the volume of cytoplasmic water. It is unlikely that glycine betaine is a source of glycine, as all available evidence suggests that accumulated glycine betaine is not further metabolized (11,15).…”

Studies on the Mechanism of Telavancin Decreased Susceptibility in a Laboratory-Derived Mutant

“…These enzymes metabolize choline to glycine betaine, 14 a compatible solute involved in osmoregulation that has beneficial effects on the protein structure. 31 In addition, there was upregulation of the heat shock protein genes clpP, htrA, and groES (about 1.9-fold).…”