Jasper P, Silver S
J Bacteriol. 1978 Mar;133(3):1323-8. doi: 10.1128/jb.133.3.1323-1328.1978.
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.
在荚膜红假单胞菌的需氧生长、异养生长以及光合生长的细胞中，均发现了用于能量依赖性摄取Mg2+和Mn2+的独立二价阳离子转运系统。光合细胞与需氧细胞摄取Mg2+的最大速率有所不同，而Mg2+转运系统的Km值恒定。处于光合对数中期的细胞摄取Mg2+的Km值约为55微摩尔，摄取Mn2+的Km值约为0.5微摩尔。这两个系统的Vmax值也存在差异：Mg2+摄取的Vmax为每克（干重）细胞0.6至1.8微摩尔/分钟，而Mn2+摄取的Vmax仅为每克0.020微摩尔/分钟，这体现了“大量需求”系统与在微量营养水平下起作用系统之间的区别。完整的荚膜红假单胞菌细胞通常不摄取钙。然而，从光合细胞中分离出的载色体膜可通过能量依赖性过程摄取Ca2+。
