Session Title: Novel Technologies and Methods: Functional Community Analysis
Presentation Date: Thursday, August 21, 2008
Poster Board Number: 0263
LINKING STRUCTURE AND FUNCTION IN SYNTROPHIC BUTYRATE-DEGRADING CONSORTIA - INTEGRATING CULTIVATION AND RNA STABLE ISOTOPE PROBING
M. Altinbas1, K. Roest2, C.M. Plugge2, I. Ozturk1, A.J.M. Stams2, H. Smidt2
1Istanbul Technical University, Department of Environmental Engineering, Istanbul, Turkey, 2Wageningen University, Laboratory of Microbiology, Wageningen, Netherlands
Butyrate is an important intermediate of organic matter conversion under methanogenic conditions, accounting for up to 60% of methanogenesis in anaerobic bioreactors. The degradation of this intermediate depends on the syntrophic interaction of butyrate-oxidizing bacteria with hydrogen utilizing organisms. However, knowledge with respect to the degradation of butyrate is mostly limited to a few pure cultures, and the structure of butyrate degrading mixed cultures active in anaerobic bioreactors has not yet been characterized by culture-independent approaches. The objective of this study was therefore to elucidate structure-function relationships within syntrophic butyrate-oxidizing consortia, employing complementary culture-dependent and -independent techniques.
A combination of cultivation-based methods with a molecular biological approach was used to reveal the dominant syntrophic butyrate degraders in laboratory-scale UASB reactors. The application of MPN dilution enrichment techniques allowed estimating the numbers of different tropic groups in the reactor biomass, focusing on sulfate-reducers, acetogens and methanogens. Highest dilution cultures that yielded growth were examined to identify the dominant populations using cloning and sequencing of 16S rRNA gene fragments. In addition, active butyrate-degrading microorganisms were identified by using a combined approach of RNA-based DGGE fingerprinting of RT-PCR-amplified 16S rRNA fragments, cloning and sequencing together with RNA-Stable Isotope Probing (SIP) with 13C-labeled butyrate and propionate. These analyses indicated that populations most closely related to Syntrophomonas spp. were the dominant, but not the only butyrate-degrading bacteria active in the reactor. In conclusion, this study provided novel leads for the identity of syntrophic butyrate-oxidizing bacteria, and their isolation and further physiological and genomic characterization.