CHARACTERIZATION OF AMINO-ACID TRANSPORT IN MEMBRANE-VESICLES FROM THE THERMOPHILIC FERMENTATIVE BACTERIUM CLOSTRIDIUM-FERVIDUS

Amino acid transport was studied in membrane vesicles of the thermophilic anaerobic bacterium Clostridium fervidus. Neutral, acidic, and basic as well as aromatic amino acids were transported at 40 degrees C upon the imposition of an artificial membrane potential (delta psi) and a chemical gradient of sodium ions (delta microNa+). The presence of sodium ions was essential for the uptake of amino acids, and imposition of a chemical gradient of sodium ions alone was sufficient to drive amino acid uptake, indicating that amino acids are symported with sodium ions instead of with protons. Lithium ions, but no other cations tested, could replace sodium ions in serine transport. The transient character of artificial membrane potentials, especially at higher temperatures, severely limits their applicability for more detailed studies of a specific transport system. To obtain a constant proton motive force, the thermostable and thermoactive primary proton pump cytochrome c oxidase from Bacillus stearothermophilus was incorporated into membrane vesicles of C. fervidus. Serine transport could be driven by a membrane potential generated by the proton pump. Interconversion of the pH gradient into a sodium gradient by the ionophore monensin stimulated serine uptake. The serine carrier had a high affinity for serine (Kt = 10 microM) and a low affinity for sodium ions (apparent Kt = 2.5 mM). The mechanistic Na+-serine stoichiometry was determined to be 1:1 from the steady-state levels of the proton motive force, sodium gradient, and serine uptake. A 1:1 stoichiometry was also found for Na+-glutamate transport, and uptake of glutamate appeared to be an electroneutral process

Na+ as coupling ion in energy transduction in extremophilic Bacteria and Archaea

For microorganisms to live under extreme physical conditions requires important adaptations of the cells. In many organisms the use of Na+ instead of protons as coupling ion in energy transduction is associated with such adaptation. This review focuses on the enzymes that are responsible for the generation and utilization of Na+ gradients in extremophilic microorganisms. Aspects that are dealt with include: bioenergetics and ion homeostasis in extremophilic Bacteria and Archaea; the molecular mechanism of Na+ translocation; and (dis)advantages of Na+ as coupling ion in energy transduction.

Supporting young adults on the autism spectrum towards independence: Lessons from the Netherlands

How can service providers help young adults on the autism spectrum find their way towards successful independent living? What factors need to be taken into account, what promotes independence and a good quality of life, and what might barriers might there be? The researchers decided to gain views directly from six young men under the age of 30 who were living in different types of residential settings in different locations