The bioenergetic basis for the decrease in metabolic diversity at increasing salt concentrations: implications for the functioning of salt lake ecosystems

摘要: Examination of the microbial diversity in hypersaline lakes increasing salt concentrations shows that certain types dissimilatory metabolism do not occur at highest salinities. Examples are methanogenesis from hydrogen and carbon dioxide or acetate, sulfate reduction with oxidation autotrophic nitrification. The observations can be explained on basis energetic cost haloadaptation used by different metabolic groups free-energy change associated reactions. All halophilic microorganisms spend large amounts energy to maintain steep gradients Na+ K+ across their cytoplasmic membrane. Most Bacteria also methanogenic Archaea produce high intracellular organic osmotic solutes a cost. aerobic (order Halobacteriales) fermentative Halanaerobiales) use KCl as main solute. This strategy, while requiring far-reaching adaptations machinery, is energetically more favorable than production compatible solutes. By combining information amount available each physiological group strategy cope stress, coherent model emerges provides explanations for upper salinity limit which conversions lakes.