Table 2.

Relative contributions of the three microbial abundance categories (rare biosphere, intermediate abundance, and dominant genera) to cobalamin synthesis or transport (evaluated by cob/cbi/bluB or btuB gene, respectively). Relative contributions are evaluated by the proportion of genes (cob/cbi/bluB or btuB) in the metagenomes within each category. The rare biosphere refers to genera whose individual relative abundances are less than 0.1%; intermediate abundance genera: 0.1–5%; dominant taxa: >5%. Group A is corrin ring biosynthesis, Group B is final synthesis and repair, and Group C is 5,6-dimethylbenzimidazole (DMB) synthesis (Fig. 1). Only annotated genera are included in the three categories (rare, intermediate, and dominant) in this table. Proportions for unclassified genera are shown at the bottom

Abundance category	Group A (%)	Group B (%)	Group C (%)	btuB (%)
Rare	45.4	45.4	41.9	50.5
Intermediate	50.9	49.0	51.7	34.7
Dominant	1.0	3.6	0.9	3.6
Unclassified	2.7	2.0	5.5	11.2