Glucose transport in isolated prosthecae of Asticcacaulis biprosthecum

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Prosthecae are specialized cellular extensions found in certain bacteria, such as Asticcacaulis biprosthecum.
• Understanding nutrient transport mechanisms in bacterial prosthecae is crucial for comprehending their unique physiology and ecological roles.

Purpose of the Study:

• To investigate the active transport of glucose in prosthecae isolated from Asticcacaulis biprosthecum.
• To characterize the kinetic properties and energy dependence of the glucose transport system.

Main Methods:

• Utilized isolated prosthecae from Asticcacaulis biprosthecum for transport assays.
• Employed a non-physiological electron donor, N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride, to stimulate transport.
• Assessed glucose uptake kinetics, stereospecificity, and inhibition by various chemical agents (e.g., NEM, PCMB, CCCP, KCN) and energy metabolism inhibitors.

Main Results:

• Identified two glucose transport systems in prosthecae with high (Km = 1.8 µM) and low (Km = 34 µM) affinities.
• Observed significant intracellular accumulation of glucose (60-200 times external concentration).
• Demonstrated stereospecificity for D-glucose and inhibition by sulfhydryl reagents and uncouplers, indicating an active, energy-dependent process not directly reliant on ATP.

Conclusions:

• The prosthecae of Asticcacaulis biprosthecum possess distinct high- and low-affinity glucose transport systems.
• Glucose transport is an active, stereospecific process that is sensitive to electron transport chain inhibitors and uncouplers.
• Evidence suggests that adenosine triphosphate (ATP) is not directly involved in powering this glucose transport mechanism.