Comparative Study of the Energy Metabolism of Anaerobic Alkaliphiles from Soda Lakes

• Published in: Microbiology (New York) Vol. 73; no. 3; pp. 243 - 248
• Main Authors: Pitryuk, A. V., Detkova, E. N., Pusheva, M. A.
• Format: Journal Article
• Language: English
• Published: 01.05.2004
• Subjects: Amphibacillus tropicus; Halonatronum saccharophilum; Spirochaeta alkalica; Tindallia magadiensis
• ISSN: 0026-2617; 1608-3237
• DOI: 10.1023/B:MICI.0000032231.76403.63

We investigated the influence of inhibitors of energy metabolism and ionophores on the growth and formation of metabolic products in alkaliphilic anaerobes characterized by various catabolism types. It was shown that blockage of oxidative phosphorylation by the addition of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of F sub(1)F sub(0) ATP synthase, resulted in a complete arrest of the growth of the acetogenic bacterium Tindallia magadiensis with arginine as an electron acceptor. In the presence of pyruvate, substrate-level phosphorylation occurred. The methylotrophic methanogenic archaebacterium Methanosalsus zhilinae did not grow with DCCD and vanadate, an inhibitor of [E sub(1)E sub(2)] ATPase, suggesting the presence of two ATPase types in this species. In the saccharolytic alkaliphiles Halonatronum saccharophilum, Amphibacillus tropicus, and Spirochaeta alkalica (which are characterized by different pH optima), the contribution of the H super(+) gradient to the energy metabolism and, presumably, to the maintenance of the intracellular pH level decreased with an increase in the degree of alkaliphily. Based on the data of an inhibitor assay using protonophores, monensin, and amiloride, we suggest that all of the bacteria tested depend on H super(+) and Na super(+) gradients. The Na super(+)/H super(+) antiport appears to be a universal mechanism of regulating the intracellular pH level and the interaction between the Na super(+) and H super(+) cycles in bacterial cells cultivated under alkaline conditions.