Fig. 1

Bacterial community structure in healthy controls and COPD patients at different stages (AECOPD, recovery, and stable COPD, respectively). a Comparison of sputum microbiome alpha richness and diversity (Shannon index, Simpson’s index, Chao1, and Observed species) by Wilcoxon rank-sum test. *p < 0.05, **p < 0.01. b Principal coordinates analysis (PCoA) based on Bray–Curtis’s distance is represented. Each point represents one subject and different colors represent different groups. ADONIS analysis showed that the separation of bacterial communities was significant (p < 0.05) as described in the text, except for stable vs controls (p = 0.066), AECOPD vs recovery (p = 0.057). c Venn diagram showing different OTUs among groups