The study of archaeal microbiota is currently hindered by methodological constraints and a constant expansion of this life Domain. In amplicon sequencing surveys, the use of universal primers eventually results in a PCR bias, overlooking different archaeal taxons. Furthermore, archaeal taxonomic structure obtained with universal primers still cannot explain the methanogenic activity observed in biogas reactors. In this work, we used reported specific primers, in order to explore the Archaeome of tree full-scale reactors treating brewery (B1 and B2) and malting (M) wastewater. We compared the dominant taxons with specific methanogenic activity test results using acetate or CO2/H2 as substrates. We analysed the V4 region of the 16S rRNA sequences in fresh sludge samples using the primer ser 340F-787R (Pinto et al., 2012, Yu et al., 2005). Specific acetoclastic and methanogenic activity tests were performed in each sample. The orders Methanosarcinales (Methanosaetaceae) and Methanobacteriales (Methanobacteriaceae) were dominant groups in all the reactors. However, the presence of a high abundance of methylotophic members (Methanomethylophilaceae) in the malt processing plant (M) reactor was also observed. The relative abundance of different taxons were summed and grouped in Acetoclastic, Hydrogenotrophic and Methylotrophic (Figure 1). The results showed a higher abundance of acetoclastic methanogens in all reactors, however this was not in accordance with the specific acetoclastic (SAMA) and hydrogenotrophic (SHMA) methanogenic activities tested in the same sludge samples. These differences could be explained by a primer bias in the detection of hydrogenotrophic methanogens, or an inhibited acetoclastic methanogenic activity. Further RNA based analysis and metagenomic approaches are still necessary to link activity to archeome structure.
Figure 1. Double axis plot showing accumulated abundances of hydrogenotrophic, acetogenic and methylotrophic taxons and specific methanogenic activities (SAMA y SHAMA).
Acknowledgement. This work was supported by local grant CSIC grupos 2019.
