On the mechanism of solute uptake in Pseudomonas.

Pseudomonas species have over 300 known and putative nutrient uptake systems enabling them to metabolize a large number of organic compounds, and thus inhabit many diverse ecological niches. The outer membrane of these organisms acts as a semi-permeable barrier, excluding many classes of potentially toxic molecules from the cell. Nutrients use specialized water-filled channels called porins to traverse this barrier. Entry into the cell is mediated by one of four classes of cytoplasmic membrane transporters: glycerol facilitators, phosphotransferase systems, primary active transporters, and secondary active transporters. The class of transporter used is dependent on the environmental conditions, as well as the type and concentration of solute. The recent advances in elucidating the structures and functional mechanisms of these uptake systems will be discussed in this review.