## 3 Results
### Analysis of Bacterial Communities of Sichuan Bacon in Different Geographical Regions  
The differences between the bacterial communities was compared in the samples collected from three regions of Sichuan to investigate the association between sampling location and bacterial communities (Figure 3). For PCA analysis (Figure 3A), there were 22.36% and 13.23% total variations in the first and the second components, respectively. PCA analysis showed that the samples collected from the basin region could be clustered together in small ranges. Interestingly, only a part of the mountains and plateau samples were clustered with the basin group, and the remaining samples were scattered long distance. PCoA (PC1 58.43% and PC2 15.32%, Figure 3B) and NMDS (stress: 0.081, Figure 3C) analysis based on the Weighted Unifrac distance showed a similar clustering pattern in the bacterial structures for the three groups. Moreover, a significant test of the community structure difference between groups based on the Anosim nonparametric test method of OTU relative abundance showed that there was a significant difference (\(p<0.05\), data not shown) between the basin and mountains, basin and plateau, mountains and plateau, or basin, mountains, and plateau. Considered together, the bacterial diversity of Sichuan bacon in different geographical regions showed a certain specificity as well as similarity. It is believed that long-term regular processes in spontaneous fermentation food often leads to a stable microbiota, among which only the best-adapted strains will occur [33]. On the contrary, microbial communities are strongly influenced by external environment conditions, such as a low environment temperature due to a production date from December of the current year to January of the following year, a high level of salt stresses due to formulation, or low water activity due to the long production cycle in meat ripening.  
Figure 2: The relative abundances of bacterial compositions of different bacons (**A**) at the phylum level and (**B**) at the genus level.  
LefSe analysis was able to identify statistically significant biomarkers, which were bacterial taxa about significant differences between the groups. The taxon nodes were displayed in terms of LDA scores >4 (Figure 11), and a few predominant genera are illustrated in Figure 4. The relative abundances of _Lactobacillus_ in the mountains and plateau groups were much higher than those in the basin group (Figure 4A), while the opposite was true for _Staphylococcus_. The results showed that there was a negative correlation in the relative abundance between _Lactobacillus_ and _Staphylococcus_, which is perhaps one of the most important factors in shaping the typical style of Sichuan bacon. Interestingly, the relative abundances of _Lactococcus_ in the plateau group (Figure 4B), similar to _Enterococcus_ (not listed), were much higher than those in the basin and mountains groups. These genera also can produce a large amount of organic acid, such as acetic and lactic acid, during exponential growth, following conversion to the alcohols and ketone that contribute a richer flavor and aroma to the product [34,35]. It is suggested that _Lactococcus_ and _Enterococcus_ are the predominant acid-producing bacteria rather than _Lactobacillus_ in the plateau group. Moreover, the relative abundances of _Brochotrix_ in the basin group were much higher than those in the mountains and plateau groups (Figure 4C), while the relative abundances of _Pseudomonas_ from the basin group were much lower than those from the mountains and plateau groups (Figure 4D). Although there were undesirable microorganisms present in all samples of Sichuan bacon due to outdoor ripening processing, the undesirable microflora was different between regions, which means that different strategies should be prepared to ensure the safety of the products.