## 3 Results
### Microbial Community Composition and Difference between S- and N-NXDQ  
The relative abundance (more than 1%) of microbiota composition at phylum and genus level is shown in Figure 3. Four bacterial phyla, including Firmicutes, unclassified_K_Bacteria (UN_K_Bacteria), Proteobacteria and Actinobacteria (Figure 3a), and two fungal phyla, including Ascomycota and Mucoromycota (Figure 3b), were found to be the dominant phyla, which accounted for more than 98% of the total microorganisms. There was no obvious difference in the composition of bacterial and fungal phyla between S- and N-NXDQ, while the average relative abundance of the dominant three fungal phyla in MYP_N was higher than that in MYP_S, respectively. Sixteen bacterial genera and fourteen fungal genera were found. The dominant bacterial genera were UN_k_Bacteria, Staphylococcus, Bacillus, Thermoactinomyces, Weissella, UN_f_Enterobacteriaceae and Kroppenstedtia (Figure 3c). Furthermore, the average abundance of Staphylococcus (29.65%) and Weissella (10.33%) in S-NXDQ was obviously higher than that (17.28% and 2.98%) in N-NXDQ, while the average abundance of Bacillus (26.75%) and Thermoactinomyces (9.44%) in N-NXDQ was higher than that (13.58% and 7.24%) in S-NXDQ. The fungal genera was dominated by Thermoascus, Aspergillus, Thermomyces, Rhizumor and Saccharomyces (Figure 3d). Meanwhile, Thermoascus was relatively higher in S-NXDQ (82.09%) than that in N-NXDQ (48.96%). On the contrary, Aspergillus presented the highest average abundance in N-NXDQ (24.52%), especially in MYP_N (39.26%), which was obviously higher than that in S-NXDQ (3.84%). Thermoascus and Aspergillus accounted for more than 74% of the fungal community in N-NXDQ. In addition, the average abundance of Rhizumor and Saccharomyces in N-NXDQ was higher than that in S-NXDQ.  
Figure 3: Relative abundance of the microbial communities in S-NXDQ and N-NXDQ samples. (**a**) Bar plots of bacterial communities at the phylum level. (**b**) Bar plots of fungal communities at the phylum level. (**c**) Bar plots of bacteria at the genus level. (**d**) Bar plots of fungi at the genus level.  
Based on the linear discriminant analysis (LDA) effect size (LEfSe) and Wilcoxon rank-sum test, the variance in microorganisms in the two grades of NXDQ are shown in Figure 4. Eleven bacterial genera and thirteen fungal genera were identified as differential taxa with significantly different relative abundance (\(p<0.05\)). MSH_N and MYP_N had more differential bacteria and fungi, respectively. _Curvibacter_, _Macrococcus_ and _Thermoactinomyces_ were significantly enriched in MYP_S, MSH_S and MSH_N samples, respectively. Meanwhile, _Candida_, _Thermomyces_, _Thermoascus_ and _Aspergillus_ were enriched in MSH_S, MSH_N, MYP_S and MYP_N samples, respectively. The rank-sum test showed that _Pseudoxanthomonas_, _Cell Vibrio_ and _Parapedobacter_ in S-NXDQ were significantly higher than those in N-NXDQ. In the fungal genera, except for _Thermoascus_, the relative abundance of the other six fungal genera in N-NXDQ was significantly higher than that in S-NXDQ. These differential bacteria and fungi could be used as biomarkers.  
Figure 4: The variations of the microbial communities in two grades of NXDQ based on linear discriminant analysis (LDA) effect size (LEfSe) and Wilcoxon rank-sum test. (**a**) The LDA score indicated the discriminant level of bacterial genera. (**b**) The LDA score indicated the discriminant level of fungal genera. (**c**) Comparison of variance bacterial genera. (**d**) Comparison of variance fungal genera. LDA > 3.5, \(p<0.05\), the levels of significance: * 0.01 \(<p\leq 0.05\); ** \(p\leq 0.01\).