FIG 2.

Abundance of N-cycling genes and their distribution across soil ecosystems. (A) Abundance of hallmark genes for denitrification, DNRA, and nitrogen fixation pathways, represented as genome equivalents (% of total bacterial genomes sampled that carry the gene) in the metagenomes studied (see figure key). (B) Frequency of genomes carrying the respective denitrifying gene across the three ecosystems studied. Genes denoted by the same letter are not statistically significantly different between ecosystems (analysis of variance [ANOVA] Tukey test). Statistical significance reported at P < 0.05. Note that nitrification genes were not detected in any of the Puerto Rico sites.