Bioenergetic properties of alkalophilic Bacillus sp. strain C-59 on an alkaline medium containing K2CO3.
Alkalophilic Bacillus sp. strain C-59 could grow well on an alkaline medium containing K2CO3, as well as Na2CO3, but did not grow on K+-depleted medium. Right-side-out membrane vesicles, energized in the absence of Na+, however, could not take up [14C]methylamine actively, while vesicles equilibrated with 10 mM NaCl actively took up [14C]methylamine. The uptake of [14C]serine was also stimulated by the addition of Na+, and the imposition of a sodium gradient caused transient uptake. These results indicated that an Na+/H+ antiporter was involved in pH homeostasis and generation of an electrochemical sodium gradient in strain C-59 even though a growth requirement for Na+ was not evident. The efflux of 22Na+ from 22Na+-loaded vesicles was more rapid at pH 9.5 than at pH 7 in the presence of an electron donor. On the other hand, vesicles at pH 7 showed more rapid efflux than at pH 9.5 when the antiporter was energized by a valinomycin-mediated K+ diffusion potential (inside negative).
Kitada
M
M
Riken Institute, Saitama, Japan.
Horikoshi
K
K
D001407:Bacillus / Q000254:growth & development / Q000378:metabolism*; D001693:Biological Transport, Active; D002254:Carbonates / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003470:Culture Media; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers
D002254:Carbonates; D002352:Carrier Proteins; D003470:Culture Media; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; C037593:potassium carbonate; D011188:Potassium