ISSN:
1432-072X
Keywords:
Interspecies H2-transfer
;
H2-threshold
;
Sulfate-reduction
;
Nitrate-reduction
;
Methanogenesis
;
Competition for H2
;
Gibbs free energy change
;
Thermodynamics
;
Electron acceptor
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The effect of different electron acceptors on substrate degradation was studied in pure and mixed cultures of various hydrogenotrophic homoacetogenic, methanogenic, sulfate-reducing, fumarate-reducing and nitrate-ammonifying bacteria. Two different species of these bacteria which during organic substrate degradation produce and consume hydrogen, were cocultured on a substrate which was utilized only by one of them. Hydrogen, which was excreted as intermediate by the first strain (and reoxidized in pure culture), could, depending on the hydrogen acceptor present, also be used by the second organism, resulting in interspecies hydrogen transfer. The efficiency of H2 transfer was similar when methanol, lactate or fructose were used as organic substrate, although the free energy changes of fermentative H2 formation of these substrates are considerably different. In coculture experiments nitrate or fumarate〉sulfate〉 CO2/CH4〉sulfur or CO2/acetate were the preferred electron acceptors, and an increasing percentage of H2 was transferred to that bacterium which was able to utilize the preferred electron acceptor. In pure culture the threshold values for hydrogen oxidation decreased in the same order from ≤1,100 ppm for homoacetogenic bacteria to about 0.03 ppm for nitrate or fumarate reducing bacteria. The determined H2-threshold values as well as the percentage of H2 transfer in cocultures were related to the Gibbs free energy change of the respective hydrogen oxidizing reaction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00411655
Permalink
