Page 90 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 4. Robustness of coal microbial community after nutrient amendment
Figure 2. Phylogenetic analysis of the microbial community at 17 and 25 months based on 16S/18S rRNA genes. A) bacterial taxonomy using 17 months and 25 months amplicon 16S rRNA gene data and 25 months metagenome bacterial 16S rRNA reads; B) relative abundance of bacteria, archaea and fungi (eukarya) based on total metagenome 16S/18S rRNA gene mapped reads at 25 months.
Community shifts from Anaerolinaceae to Rhodocyclaceae as dominant potential complex organic compound degraders
At 17 months, the Anaerolinaceae were quite abundant (15% of 16S rRNA gene reads, Fig. 2) but almost completely disappeared at 25 months (< 0.2%). They were replaced by the Rhodocyclaceae comprising the genera Azoarcus and Thauera that were virtually absent at 17 months (< 0.4% of 16S rRNA gene reads) but became dominant community members at 25 months (23% of bacterial 16S rRNA gene reads in the amplicon survey; 44% relative abundance in the metagenome, Fig. 2). As there is no metagenome from the 17-month sample available and Anaerolinaceae were nearly absent at 25 months, a functional potential can only be inferred. Interestingly, their potential in coal degradation has not been suggested previously. However, Anaerolineaceae were dominant after long-term enrichments with long-chain n- alkanes-dependent methanogenic conditions and occur in combination with sulfate reducers and methanogens (Methanoculleus and Methanothrix) (Liang et al. 2015, 2016). In addition, enrichment from aquifer sediment with naphthalene (a polycyclic aromatic hydrocarbon) showed high relative abundance of Anaerolineaceae (5.7%-47.0%) and experimental evidence showed that polycyclic aromatic hydrocarbon (PAH) dioxygenases are present in
88