Syntrophic Co-culture Studies
Sponsor: DOE Office of Biological and Environmental Research; PNNL's Biomolecular Sciences Initiative
Contacts: Johannes Scholten, Weiwen Zhang, and Fred Brockman
Syntrophy means "feeding together" two syntrophic co-cultures are being studied. Syntrophy is the inability of either microorganism by itself to grow on a compound, yet when the two organisms work together they are able to both gain energy for growth from the compound. The syntrophic partnership is based on one partner maintaining the concentration of a product at an extremely low level so that product formation is not inhibited due to thermodynamic considerations. Understanding syntrophic relationships at the molecular genetic level will enable future understanding of other syntrophic relationships and the ensemble of such relationships in anaerobic microbial communities where many conversions occur at (Gibbs) free energy changes very close to thermodynamic equilibrium.
Two syntrophic co-cultures are being studied. The goal of the Desulfovibrio vulgaris-Methanosarcina barkeri co-culture project is to identify genome-wide metabolic networks in the syntrophic relationship and to understand how the syntrophic partnership modulates the partners' expression and biochemical machinery compared to those of the pure cultures. Metabolic networks will be determined for each organism and compared to the networks present when they are grown in a syntrophic co-culture. Batch and continuous cultures will be studied. Whole-genome DNA microarrays and proteomics technologies will be applied to profile gene expression and protein abundance and the data will be analyzed to identify active modules and metabolic networks. Of particular interest are the genes and networks differentially expressed in pure culture and syntrophic co-culture.
The goal of the Syntrophobacter fumaroxidans-Methanospirillum hungatei co-culture project is to identify the differences in proteins and metabolic networks under conditions that support a near maximum, a tenfold reduced, and an essentially zero growth rate. These organisms are currently being sequenced by the Department of Energy. Protein profiling will characterize genome-wide expression under the different conditions, RNA will be archived for future analysis, and the bioenergetics of the different growth rates will be characterized. This research will develop novel, genome-wide information on how microbes reprogram their genetic and biochemical machinery when exposed to the same substrate but under widely varying substrate flux.