Melatonin or probiotics treatment alleviated gut microbiota disorders in NP exposure mice (n = 6). (a) Distribution of OTUs in the four groups. (b) The sequencing depth was characterized by Shannon–Wiener curves for all samples. (c) Number of sequences detected in each group. (d) PCoA plot analysis. (e) and (f) Differential gut microbial identification by LEfSe analysis (linear discriminant analysis (LDA) > 4). (g) Correlation between differential gut microbiota and hematopoietic damage by Spearman analysis. (h)–(k) Relative abundances of key microbiota at the family, species, genus, and order level, respectively. Values were presented as median ± quartile. Differences were assessed by Mann Whitney test and denoted as follows: *p < 0.05, **p < 0.01, ns: p > 0.05.