Transport and phosphorylation of glucose, fructose, and mannitol by Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa, when grown on d-glucose, was shown to possess both a specific glucose transport system and a high level of glucokinase (EC 2.7.1.2; adenosine 5′-triphosphate: d-glucose 6-phosphotransferase). Growth on d-fructose resulted in the induction of fructokinase (EC 2.7.1.4; adenosine 5′-triphosphate: d-fructose 6-phosphotransferase), and a transport system for fructose was formed. Growth on mannitol resulted in the induction of ( 1), mannitol dehydrogenase (EC 1.1.1.67; mannitol:inicotinamide-adenine-dinucleoide oxidoreductase); ( 2), a high level of fructokinase; and ( 3), a transport system for mannitol. Mannitol-grown cells also exhibited a slower rate of fructose uptake and oxidation. Fructose uptake by mannitol-grown cells was not mediated by the mannitol transport system but, apparently, occurred by simple diffusion when coupled to phosphorylation and subsequent catabolism. Similarly, simple diffusion of fructose and mannitol into glucose-grown cells was also observed, but these substrates were not concentrated or further catabolized due to the absence of specifically inducible fructokinase and mannitol dehydrogenase. The phosphoenolpyruvate:hexose phosphotransferase system was not detected in cell-free extracts from this organism. Instead, the sugar phosphorylation reactions detected were dependent upon adenosine 5′-triphosphate and enzymes in the soluble fraction of crude extracts. Mannitol, methyl α-glucoside, methyl β-glucoside and N-acetylglucosamine were not phosphorylated in cell-free extracts from cells grown on glucose, fructose, or mannitol when either adenosine 5′-triphosphate or phosphoenolpyruvate was supplied as a phosphoryl donor. Methyl α-glucoside, methyl β-glucoside, and N-acetylglucosamine were not transported by resting cells that were grown on glucose or fructose. It could not be discerned from the experimental evidence whether carrier mediated transport of carbohydrates was due to active transport or to facilitated diffusion. These data support the conclusion, however, that carbohydrates are transported in an unaltered state by P. aeruginosa and are trapped intracellularly by phosphorylation via specific kinases.