Observed operational taxonomic units (OTUs) and oral OTU-level bacterial diversity in lung cancer cases and controls. (A) Shared and unique OTUs observed among lung cancer cases and controls of European Americans and African Americans. (B) Comparing mean observed OTUs and three alpha diversity indexes (Chao1, PD whole tree, and Shannon) between lung cancer cases and controls (paired t-test, all P>0.05). (C) Principal coordinates analysis (PCoA) of Bray-Curtis beta diversity (P=0.93 from PERMANOVA-S, permutation number=1,000,000).