Sodium ATPase and sodium/proton antiporter are not obligatory for sodium homeostasis of Enterococcus hirae at acid pH.
Enterococcus hirae grows in a broad pH range from 5 to 11. An E. hirae mutant 7683 lacking the activities of two sodium pumps, Na+-ATPase and Na+/H+ antiporter, does not grow in high Na+ medium at pH above 7.5. We found that 7683 grew normally in high Na+ medium at pH 5.5. Although an energy-dependent sodium extrusion at pH 5.5 was missing, the intracellular levels of Na+ and K+ were normal in this mutant. The Na+ influx rates of 7683 and two other strains at pH 5.5 were much slower than those at pH 7.5. These results suggest that Na+ elimination of this bacterium at acid pH is achieved by a decrease in Na+ entry and a normal K+ uptake.
Ikegami
M
M
Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Takahashi
H
H
Igarashi
K
K
Kakinuma
Y
Y
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001693:Biological Transport, Active; D027682:Cation Transport Proteins; D016983:Enterococcus / Q000378:metabolism*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D027682:Cation Transport Proteins; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D011188:Potassium