Title: Terephthalate degradation through multiple syntrophic interactions revealed by metagenomic and metatranscriptomic analysis

Presenter: Dr. LI Xiangzhen

University: Center for Advanced BioEnergy Research, the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign, US

Time: 15:00-16:00, 21 March, 2011

Venue: A102, Institute of Microbiology, Chinese Academy of Sciences

Abstract:

Metagenomics and metatranscriptomics are based on the analysis of microbial DNA and RNA that are extracted directly from microbial communities in environmental samples. They are powerful tools that can be used to analyze microbial community composition and metabolic potentials without cultivations. Metagenomics provides information on the potential metabolic activities of a microbial community. However, metatranscriptomics can trace those genes that are actively transcribed at a particular time and specific conditions, and ultimately to identify what is responsible for the difference. Next generation sequencing techniques greatly promote the applications of these methods. In this seminar, next generation sequencing technique and its applications will be briefly introduced. Then, a study will be discussed using metagenomics and metatranscriptomics to investigate the key metabolic pathways and microbial interactions in a terephthalate (TA)-degrading methanogenic consortium. 

Terephthalate-containing wastewater is produced at large quantity and in high concentration in plastic industry. Prior to discharge, the wastewater is commonly treated using anaerobic methanogenic reactors. TA degradation pathways and microbial interactions in anaerobic TA-degradation systems are not fully understood. In our research, a laboratory-scale bioreactor for treating TA was operated at hyper-mesophilic conditions (46-50oC) for four years. We used metagenomic and metatranscriptomic approaches to study the putative TA degradation pathways, the responsible microorganisms, and multiple syntrophic interactions in this system. Pelotomaculum spp. were consistently observed as the most important bacterial population together with three different novel methanogens, one related to Methanolinea tarda and two related to Methanosaeta concilli. These four populations formed a primary syntrophic interaction. Based on the genes predicted, they could participate in the degradation of TA using pathways that involve in decarboxylation, dearomatization and b-oxidation to hydrogen/CO2 and acetate, and finally to methane and CO2.

Metatranscriptomic data indicated that highly expressed genes in reactor mainly originated from Methanolinea, followed by uncultured Methanosaeta, Pelotomaculum, Kosmotoga, WWE1, OP5, confirming their important roles in TA-degradation. Novel genes involved in TA degradation to acetate and H2/CO2 in Pelotomaculum sp. were actively expressed. Some genes involved in acetyl-CoA fermentation to butyrate from Pelotomaculum and OP5 were actively expressed, indicating that butyrate may be an important intermediate besides H2/CO2 and acetate. Kosmotoga and Syntrophus are potential microorganisms to oxidize butyrate into H2/CO2 and acetate. Butyrate production triggers secondary syntrophic interaction, which serve to maintain the stability of anaerobic process.