Desulfosporosinus infrequens sp. nov.

MAG SbF1 obtained from a wetland in Germany. A major driver of sulfate reduction in experimental microcosms established with acidic soil from the Schlöppnerbrunnen II fen (Bavaria, Germany).

The population genome of the low-abundance Desulfosporosinus species was obtained by coassembly and differential coverage binning of metagenomes obtained from native peat soil and 13C-labeled fractions of a DNA-stable isotope probing experiment of the same peatland (see Fig. S1in the supplemental material) (29). The high-quality metagenome-assembled genome (MAG) SbF1 had a size of 5.3 Mbp (on 971 scaffolds), a G+C content of 42.6%, a CheckM-estimated completeness of 98.0%, a potential residual contamination of 3.9%, and 10% strain heterogeneity. Besides 16S and 23S rRNA genes, SbF1 carried 6,440 protein-coding genes (CDS), five 5S rRNA gene copies, 59 tRNAs, and 37 other ncRNAs, making a total of 6,543 predicted genomic features. The genome size and G+C content were in the same range as observed for genomes of cultured Desulfosporosinus species (3.0 to 5.9 Mbp and 42 to 44%, respectively) (30–34). Scaffolds containing rRNA genes had a higher coverage than the average coverage of all scaffolds (Fig. S1), indicating multiple rrn operon copies, as is known from genomes of other Desulfosporosinus species (on average, 9.3 rrn operons; range, 8 to 11) (35).

Based on its phylogenetic placement and novel ecophysiological behavior, we propose that Desulfosporosinus sp. MAG SbF1 represents a novel species with the proposed name Desulfosporosinus infrequens” sp. nov. (in.fre′quens. L. adj. infrequens, rare, referring to its low relative abundance). Based on its genome-derived metabolic potential and support from metatranscriptomics,Desulfosporosinus infrequens” is capable of complete oxidation of acetate, propionate, and lactate with sulfate as the electron acceptor, with further potential for oxidation of molecular hydrogen (Fig. 1).