Na~+ and water fluxes across cell membranes of the freshwater cyanobacterium Synechococcus as reported by chlorophyll a fluorescence

摘要

Cell of fresh water cyanobacterial genus Synechococcus (e.g., S. sp. PCC 7942, hereafter S7942) import NaCl passively and export Na~+ actively, primarily via Na~+/H~+ antiport. During a salinity upshock episode, the cell volume first increases to a maximum within 2-3 min as a result of passive importation of Na~+, Cl~+, and H_2O (rise branch), and then it decays slowly (tens of minutes) to a lower steady value as a result of active exportation of Na~+ ions (decay branch; Nitschmann and Packer 1992).NaCl-induced volume changes of cyanobacterial cells are reported quantitatively by changes in the intensity of PBS-sensitized Chla fluorescence (Stamatakis et al 1999). In this research we used NaCl-induced Chla fluorescence changes in order to learn more about the active extrusion of Na~+ ions by S7942 cells and the effects of Na~+ channel blockers on Na~+ traffic through plasma membranes.