Transport and retention of K+ and other metabolites in a marine pseudomonad and their relation to the mechanism of optical effects.
Suspensions of cells of a marine pseudomonad washed with 0.05 m MgSO(4) showed an immediate increase in optical density (first-phase optical change) when the salt concentration of the suspending medium was increased; a subsequent slow decrease in optical density (second-phase optical change) occurred if K(+) was present. The rate of the second-phase change was similar to the rate of uptake of (42)K(+) by the cells. Glutamate increased the rate and extent of the second-phase change and produced a parallel increase in the rate and extent of uptake of (42)K(+). Citrate increased the extent of the second-phase change in cells adapted to oxidize citrate but not in unadapted cells. Adapted, but not unadapted, cells accumulated (14)C-citrate. The nonmetabolizable alpha-aminoisobutyric acid (AIB) also increased the extent of the second-phase change under conditions leading to the uptake of (14)C-AIB by the cells. Cells maintained in a salt solution optimal for the retention of intracellular solutes were found to contain 0.184 m K(+). In the same salt solution, cells preloaded with (42)K(+) retained the isotope, but they lost it rapidly when suspended in 0.05 m MgSO(4). The second-phase changes can be accounted for by the energy-dependent accumulation in an osmotically active form of K(+) and other metabolites by cells depleted of intracellular solutes.
D000621:Aminoisobutyric Acids / Q000494:pharmacology; D001692:Biological Transport; D002247:Carbon Isotopes; D002951:Citrates / Q000494:pharmacology; D003470:Culture Media; D005971:Glutamates / Q000494:pharmacology; D007444:Inulin / Q000378:metabolism; D007477:Ions; D008278:Magnesium Sulfate / Q000494:pharmacology; D009584:Nitrogen; D009995:Osmosis; D011188:Potassium / Q000032:analysis / Q000378:metabolism*; D011549:Pseudomonas / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000032:analysis / Q000378:metabolism; D013053:Spectrophotometry; D014871:Water Microbiology
D000621:Aminoisobutyric Acids; D002247:Carbon Isotopes; D002951:Citrates; D003470:Culture Media; D005971:Glutamates; D007477:Ions; D008278:Magnesium Sulfate; D007444:Inulin; D012964:Sodium; D009584:Nitrogen; D011188:Potassium