Fig. 3

Disparities in relative but not absolute 16S rRNA gene microbial abundance in amniotic fluid samples from preterm deliveries depending on the BPD disease severity. A AF samples from preterm deliveries from Fig. 2 were separated for the BPD disease severity into no (red), mild (green) and moderate/severe (m/s, blue) BPD. Box plots show the gene copy numbers of 16S rRNA gene per ml of AF samples and prevailed no significant difference in total bacterial load. Statistical analysis was performed using Kruskal–Wallis and Wilcoxon Rank-Sum test with Benjamini–Hochberg correction for multiple comparisons, respectively. B Box plots of different alpha (diversity indices show that richness and Shannon diversity did not differ significantly between the samples of different disease severities while evenness of mild BPD was increased. Statistical analysis was performed using Kruskal–Wallis and Wilcoxon Rank-Sum test with Benjamini–Hochberg correction for multiple comparisons, respectively. C NMDS plot of weighted Unifrac distances shows no significant (p < 0.05) difference in bacterial 16S rRNA gene community composition for samples of different disease severities. Statistical analysis was performed using PERMANOVA with Benjamini–Hochberg correction for multiple comparisons. D Heat tree including genera ≥ 0.1% of all reads. The labelled tree on the lower left shows the taxonomic information (domain to genus) and is the key for the unlabelled smaller trees. Smaller trees represent a pairwise comparison between no, mild and moderate/severe (m/s) BPD. Coloured taxa are more abundant (based on log2-transformed ratio of median proportions) in the samples indicated in the respective tree subtitle colour. Significant changes (p < 0.05 based on Wilcoxon-Rank-Sum test with FDR correction) are marked with green rectangles