Cation transport and metabolism in Streptococcus fecalis
ABSTRACT 1.1. Streptococcus fecalis maintains an intracellular K+ concentration of 559 mM and an intracellular Na+ concentration of less than 5 mM when growing exponentially in a medium containing 4.6 mM K+ and 151 mM Na+. Cells harvested from the stationary phase are K+-poor and Na+-rich.2.2. An energy-dependent net uptake of K+ is observed following resuspension of K+-poor, Na+-rich cells in a neutral medium containing both substrate and K+.3.3. Net K+ uptake under these conditions is the result of two cation-exchange processes: (i) a K+−Na+ exchange which accounts for aapprox. 60% of the total K+ uptake; and, (ii) a K+−H+ exchange utilizing H+ present in the cell at the time of harvesting.4.4. Net cation transport is absolutely dependent on the metabolism of exogenous substrate, and both glucose and arginine will support the process, though at significantly different rates. With either substrate, the initial rate of net K+ uptake is equal to the calculated rate of ATP production.5.5. A transient two-fold increase in the glycolytic rate is closely associated with the onset of K+ uptake indicating a coupling between active cation transport and energy-yielding processes in this organism.
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ABSTRACT: Work is described on the changes in cell ions during growth of cultures of a species of Halobacterium isolated from the Dead Sea. Cell K concentration fell from 5.5 to 3.8 moles per kg cell water during the logarithmic phase of growth and maintained the latter value during the stationary phase (initial medium concentration, 7 mM). Cell Na and Cl followed a complex series of roughly parallel changes. The logarithmic phase ion concentrations were: Na, 1.0-2.3 moles/kg cell water; Cl, 2.3-3.7 moles/kg cell water. The final stationary phase values were: Na, 0.5 moles/kg cell water; Cl, 2.3-2.9 moles/kg cell water (medium NaCl concentration, 3.9 Molal). It is suggested that most of the K(+) is bound within the cytoplasm.The Journal of General Physiology 03/1970; 55(2):187-207. · 4.73 Impact Factor