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 K m of 7 μM. Free glucose was concentrated intracellularly by P. aeruginosa PAO 57 over 200-fold 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 α- d -glucose (α-MeGlc) via the glucose transport system. The apparent K m of α-MeGlc transport was 7 mM which indicated a 1,000-fold lower affinity of the glucose transport system for α-MeGlc than for glucose. While only unchanged α-MeGlc was detected intracellularly in P. aeruginosa , α-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.