Unveiling the Biodiversity of Hyperthermophilic Archaea in Jharia Coal Mines: Potential Threat to Methanogenesis?

Abstract

Aim: To examine the biodiversity of archaeal sulfate reducers and methanogens present in the underground coal mines of Jharia using metagenomics and pyrosequencing.

Objectives: 1) Bioinformatical analysis of the metagenomic data related to a taxonomic analysis obtained from the coal to investigate complete archaeal taxonomic features of the coal bed methane (CBM) microbiome. 2) Bioinformatical analysis of the metagenomic data related to a functional analysis obtained from the coal to investigate functional features relating to taxonomic diversity of the CBM microbiome. 3) The functional attributes have been examined specifically for ORFs related to sulfite reduction and methanogenesis.The taxonomic and functional biodiversity related to euryarchaeota will help in a better understanding of the obstacles associated with methane production imposed by the sulfate reducers.

Background: The microbial methanogenesis in the coal microbiome is a resultant of substrate utilization by primarily fermentative bacteria and methanogens. The present work reveals the biodiversity of archaeal sulfate reducers and methanogens present in the underground coal mines of Jharia using metagenomics and pyrosequencing.

Methodology: Bioinformatical analysis for structural and functional attributes was accomplished using MG-RAST. The structural analysis was accomplished using RefSeq database, whereas the functional analysis was done via CoG database with a cut off value, a sequence percent identity, and sequence alignment length cut off of 1e^-5, 60% and 45, respectively.

Results: Attained communities revealed the dominance of hyperthermophilic archaea Pyrococcus furiosus along with Thermococcus kodakarensis in the coal metagenome.The obtained results also suggest the presence of dissimilatory sulfite reductase and formylmethanofuran dehydrogenase, formylmethanofuran: tetrahydromethanopterin formyltransferase involved in sulfite reduction and methanogenesis, respectively, in the microbiome.

Conclusion: This report is the first attempt to showcase the existence of specific euryarchaeal diversity and their related functional attributes from Jharia coal mines through high throughput sequencing. The study helps in developing a better understanding of the presence of indigenous microbes (archaea) and their functions in the coal microbiome, which can be utilized further to resolve the energy crisis.

Keywords: Euryarchaeota; SRBs; metagenomics; pyrosequencing; sulfite reductase; thermococcales.

Fig. (1)

Rarefaction analysis of coal metagenome. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (2)

Stacked bar chart revealing the euryarchaeal diversity in the metagenome. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (3)

A. Barchart showing genus distribution in Thermococcaceae family; B. Barchart showing family distribution in Methanobacteriales order and genus distribution in Methanobacteraceae class; C. Stacked barchart revealing family distribution in Methanomicrobiales and Methanosarcinales order. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (4)

Heatmap showing the functional distribution of coal metagenome under the metabolism section. (A higher resolution / colour version of this figure is available in the electronic copy of the article).