A culture apparatus for maintaining H2 at sub-nanomolar concentrations

We devised a microbial culture apparatus capable of maintaining sub-nanomolar H-2 concentrations. This apparatus provides a method for study of interspecies hydrogen transfer by externally fulfilling the thermodynamic requirement for low H-2 concentrations, thereby obviating the need for use of cocultures to study some forms of metabolism. The culture vessel is constructed of glass and operates by sparging a liquid culture with purified gases, thereby removing H-2 as it is produced. We used the culture apparatus to decouple a syntrophic association in an ethanol-consuming, methanogenic enrichment culture, allowing ethanol oxidation to dominate methane production. We also used the culture apparatus to grow pure cultures of the ethanol-oxidizing, proton-reducing Pelobacter acetylenicus (WoAcy 1), and to study the bioenergetics of growth. (C) 2000 Elsevier Science B.V. All rights reserved.