Fig. 2

Relative abundance of the most prevalent bacteria at the phylum and genus levels in stable COPD patients. The bacterial taxonomic distributions are shown at the phylum and genus levels in the sputum microbiomes of COPD patients. The stacked bar represents differentially expressed bacteria at the phylum level (a) in different COPD phenotypic subgroups. The box and whisker plots (10–90 percentile) show the relative abundance of Proteobacteria in the LRE vs HRE groups (b) or in the PFT I and PFT II groups (c). The stacked bar represents differentially expressed bacteria at the genus level (d) in the different COPD phenotypic subgroups. The box and whisker plots show the relative abundance of Streptococcus in the LRE vs HRE groups (e) or in the PFT I and PFT II groups (f). The p value was analyzed using the Mann–Whitney Wilcoxon test. Bonferroni-adjusted p-values < 0.05/15 (5 phyla and 10 genera) = 0.0033 indicate significance. LRE low-risk exacerbator, HRE high-risk exacerbator