title: Divalent cation transport systems of Rhodopseudomonas capsulata.
abstract: Separate divalent cation transport systems for energy-dependent uptake of Mg2+ and Mn2+ were found both with aerobically and heterotrophically grown and with photosynthetically grown cells of Rhodopseudomonas capsulata. The maximum rate of Mg2+ uptake differed between photosynthetic and aerobic cells, while the Km for the Mg2+ transport system was constant. Photosynthetic midlog-phase cells exhibited Km's for uptake of about 55 micrometer Mg2+ and 0.5 micrometer Mn2+. The Vmax's also differed between the two systems: 0.6 to 1.8 mumol/min per g (dry weight) of cells for Mg2+, but only 0.020 mumol/min per g for Mn2+, making the distinction between a "macro-requirement" system and a system functioning at trace nutrient levels. Calcium was not normally taken up by intact cells of R. capsulata. However, chromatophore membranes isolated from photosynthetic cells took up Ca2+ by an energy-dependent process.
mesh_terms: D020130:Bacterial Chromatophores / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D012241:Rhodopseudomonas / Q000378:metabolism*
chemical_list: D004140:Dinitrophenols; D008345:Manganese; D004024:Dicyclohexylcarbodiimide; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D008274:Magnesium; D002118:Calcium