Abstract
Methanogenesis occurs in many natural environments and is used in biotechnology for biogas production. The efficiency of methane production depends on the microbiome structure that determines interspecies electron transfer. In this research, the microbial community retrieved from mining subsidence reservoir sediment was used to establish enrichment cultures on media containing different carbon sources (tryptone, yeast extract, acetate, CO2/H2). The microbiome composition and methane production rate of the cultures were screened as a function of the substrate and transition stage. The relationships between the microorganisms involved in methane formation were the major focus of this study. Methanogenic consortia were identified by next generation sequencing (NGS) and functional genes connected with organic matter transformation were predicted using the PICRUSt approach and annotated in the KEGG. The methane production rate (exceeding 12.8 mg CH4 L−1 d−1) was highest in the culture grown with tryptone, yeast extract, and CO2/H2. The analysis of communities that developed on various carbon sources casts new light on the ecophysiology of the recently described bacterial phylum Caldiserica and methanogenic Archaea representing the genera Methanomassiliicoccus and Methanothrix. Furthermore, it is hypothesized that representatives of Caldiserica may support hydrogenotrophic methanogenesis.
Highlights
Microbial diversity and functioning in the environment are one of the most intriguing issues in science, given that they are related to the foundations of the knowledge regarding biogeochemical cycles
We found a relationship between the contribution of Methanothrix and acetogenic bacteria
The results obtained in this study show that our current understanding of microbial processes leading to degradation of organic matter to methane is still far from complete
Summary
Microbial diversity and functioning in the environment are one of the most intriguing issues in science, given that they are related to the foundations of the knowledge regarding biogeochemical cycles. Methanogenesis is a multistage process in which degradation of complex organic molecules into simple one-carbon compounds is performed by a consortium of microorganisms [7,8]. Their existence in the natural environment is an effect of coevolution leading to the development of metabolic interactions that allow the flow of carbon, energy, and other intermediates for mutual benefit [9,10]. Ethanol and 2-propanol may be used by some methanogens instead of H2 as electron donors [11] This narrow range of substrates is delivered by bacteria, mostly from the genera Clostridium, Pseudomonas, Desulfovibrio, and Cellulomonas [14]. In freshwater lakes, is primarily decomposed by bacteria to acetate, CO2, and H2, which are the main substrates used by methanogens in two major pathways: hydrogenotrophic and acetotrophic [15,16]
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