Inhibitory analysis of the energy metabolism of the extremely haloalkaliphilic homoacetic bacterium Natroniella acetigena

The effect of ionophores and dicyclohexylcarbodiimide (DCCD) on growing cul tures of the extremely haloalkaliphilic homoacetic bacterium Natroniella ac etigena was studied. Growth and acetogenesis in media with lactate or ethan ol at optimal pH value 9.7 and a salinity of 1.57% were completely inhibite d by DCCD, a potent inhibitor of F1F0-ATPase. The protonophore tetrachloros alicylanilide and the Na+/H+ antiporter monensin produced a similar effect: growth and acetogenesis stopped instantly after the addition of these comp ounds to an 18-h culture. N. acetigena was less sensitive to amiloride, whi ch is an inhibitor of Na+ transport. Inhibitory analysis showed that the en ergy metabolism of N. acetigena depends on the generation of a transmembran e electrochemical gradient of Na+ via Na+/H+ antiport. Proton cycling via o xidative phosphorylation and F1F0-ATPase are necessary for maintaining pH-h omeostasis.