Richness of phyla and coverage by SILVA and the GPC.

(A) Estimated number of OTUs (97% similarity in the 16S-V4 region) globally, within various prokaryotic phyla. Estimated based on the coverage of SILVA by the GPC (subfigure C) and the number of OTUs in the GPC. Only phyla including at least 10 entries in SILVA (release 132, set NR99) [14] and estimated to contain at least 10 extant OTUs are considered. Phyla are sorted in decreasing estimated OTU richness; only the 25 richest phyla are shown. (B) Fraction of GPC OTUs that could be mapped to SILVA NR99 at similarity ≥97%, as a proxy for global OTU richness covered by SILVA, within the same phyla as in A. (C) Fraction of SILVA NR99 sequences that could be mapped to the GPC at similarity ≥97%, as a proxy for global OTU richness covered by the GPC, within the same phyla as in A. For additional phyla not shown here, see S6 Fig. For analogous results at other phylogenetic resolutions, see S7 Fig (99%), S8 Fig (95%), and S9 Fig (90%). For analogous results at the class level, see S10 Fig (99%), S11 Fig (97%), and S12 Fig (95%). GPC, Global Prokaryotic Census; NR, nonredundant; OTU, operational taxonomic unit.