Diverse microorganisms can execute one or more steps in denitrification, during which nitrate or nitrite is successively reduced into nitric oxide, nitrous oxide, and ultimately dinitrogen. Many of the best-characterized denitrifiers are “complete” denitrifiers capable of executing all steps in the process, but whether they dominate in natural communities and what environmental factors drive the distribution of complete vs. partial denitrifiers remain unclear and incomplete in a global context. To address this, we will conduct a comparative analysis of denitrification genes in 48,284 genomes and assessed their environmental distribution in 3,991 metagenomes and 1,700 metatranscriptomes covering all major biomes. We did the genomic and metagenomic analyses and need now to process the metratranscriptomes.