Transport of Glucose, Gluconate, and Methyl α-D-Glucoside by Pseudomonas aeruginosa

Abstract

Glucose transport by Pseudomonas aeruginosa was studied. These studies were enhanced by the use of a mutant, strain PAO 57, which was unable to grow on glucose but which formed the inducible glucose transport system when grown in media containing glucose or other inducers such as 2-deoxy-D-glucose. Both PAO 57 and parental strain PAO transported glucose with an apparent Km of 7 ,uM. Free glucose was concentrated intracellularly by P. aeruginosa PAO 57 over 200fold above the external level. These data constitute direct evidence that glucose is transported via active transport by P. aeruginosa. Various experimental data clearly indicated that P. aeruginosa PAO transported methyl a-D-glucose (a-MeGlc) via the glucose transport system. The apparent Km of a-MeGlc transport was 7 mM which indicated a 1,000-fold lower affinity of the glucose transport system for a-MeGlc than for glucose. While only unchanged a-MeGlc was detected intracellularly in P. aeruginosa, a-MeGlc was actually concentrated intracellularly less than 2-fold over the external level. Membrane vesicles of P. aeruginosa PAO retained transport activity for gluconate. This solute was concentrated intravesicularly several-fold over the external level. A component of the glucose transport system is believed to have been lost during vesicle preparation since glucose per se was not transported. Instead; glucose was converted to gluconate by membrane-associated glucose dehydrogenase and gluconate was then transported into the vesicles. Although this may constitute an alternate system for glucose transport, it is not a necessary prerequisite for glucose transport by intact cells since P. aeruginosa PAO 57, which lacks glucose dehydrogenase, was able to transport glucose at a rate equal to the parental strain.Glucose is transported by Pseudomonas aeruginosa by a specifically inducible system (3, 10). This transport system is temperature dependent, it obeys saturation kinetics, and it is inhibited by uncouplers. Evidence also indicates that glucose is transported by P. aeruginosa as the free sugar and not by the phosphoenolpyruvate: hexose phosphotransferase system (3, 10, 11).

Protein D1 — A glucose-inducible, pore-forming protein from the outer membrane of Pseudomonas aeruginosa

“…In addition, D1 was not induced by a variety of different carbon sources (Table 1). Overall, the results demonstrated that under all conditions where the high affinity glucose uptake system and the periplasmic glucose binding protein were induced [1][2][3]11,12], protein D 1 was seen in SDS polyacrylamide gel electrophoretograms of outer membranes (Table 1). There was no such correlation between induction of protein D1 and the induction of the low affinity glucose uptake system [ 1,2], the mannitol, fumarate, glycerol or dicarboxylic acid uptake systems or a variety of hexose (including glucose) catabolizing enzymes [2,4,12].…”

“…N.D., not determined. c Taken from the data of [1][2][3]11,12]: + transport of glucose occurs by the indicated system; -, no transport of glucose; N.D., not determined.…”

The inhibitory effect of the artificial electron donor system, phenazine methosulfate‐ascorbate, on bacterial transport mechanisms

“…Active transport of glucose by P. aeruginosa, on the other hand, apparently is a shock-sensitive system because a glucose-binding protein has been detected (1 2). and because membrane vesicles prepared from P. aeruginosa were unable to actively transport glucose but they retained the ability to transport gluconate (3,4) and serine (unpublished observations). On the other hand, gluconate transport by P. aeruginosa apparently is shock resistant because membrane vesicles retained the ability to actively transport gluconate (3,4).…”

“…and because membrane vesicles prepared from P. aeruginosa were unable to actively transport glucose but they retained the ability to transport gluconate (3,4) and serine (unpublished observations). On the other hand, gluconate transport by P. aeruginosa apparently is shock resistant because membrane vesicles retained the ability to actively transport gluconate (3,4). When PMS-ascorbate was tested against these 2 transport systems of P. aeruginosa, both glucose and gluconate transport were found to be as extensively inhibited as proline transport.…”

“…under the cultural conditions previously defined (3,6). The final concentration of the carbon source was 11 mM glucose for all species except P. aeruginosa PA0 57.…”