## 3 Results  
### Analysis of Bacterial Community in Shrimp Paste Samples  
The bacterial composition in shrimp paste samples was determined by high-throughput sequencing and the results are shown in Figure 1. There were 11 genera identified in the control group and 7 genera in the inoculation group, respectively. The dominant genera in both groups were _Marinilactibacillus_ and _Tetragencococcus_, with relative abundances of 85.13-38.47% and 8.83-54.16% in the control group and 19.85-22.17% and 78.13-74.82% in the test group, respectively (Figure 1A). After the starter culture inoculation, the relative abundance of _Marinilactibacillus_ at 7 and 35 days decreased by 65.28% and 16.30%, respectively. In addition to the dominant genera, some genera with less abundance (<4%), such as _Virgibacillus_, _Atopostiyes_, _Salinicoccus_, _Moritella_, _Jeogalicoccus_, and _Staphylococcus_, were further reduced in relative abundance with the inoculation of starter culture (<2%).  
Eight species were identified in both the control and test group. The predominant species in both groups were uncultured _Marinilactibacillus_, _T. muriaticus_, and _Tetragencoccus halophilus_ (_T. halophilus_), with relative abundances of 85.13-38.47%, 5.63-33.78%, and 3.20-20.38% in the control group and 19.85-22.17%, 77.91-63.83%, and 0.22-10.99% in the test group, respectively (Figure 1B). After the starter culture inoculation, the relative abundance of _T. muriaticus_ increased by 72.28% and 30.05% by Day 7 and Day 35, respectively. The relative abundance of uncultured _Marinilactibacillus_ decreased by 65.28% and 16.30% by Day 7 and Day 35, respectively. The relative abundance of _T. halophilus_ decreased by 2.98% and 9.39% by Day 7 and Day 35. In addition, some relatively low-abundance species, such as _Lentiobacillus juriscarrius_ and _Salinicoccus siamensis_, also decreased in relative abun  
Figure 1: Comparative analysis of bacterial composition in control and test groups on genus (**A**) and species (**B**) level. Relative abundance of bacteria is presented as mean values, measured in triplicate. C: samples without starter culture; T: samples with starter culture. 7, 35: fermentation time (in days).  
dance after the inoculation of the starter culture. The inoculation resulted in a significant difference in the abundance of the bacterial genera and species.  
Principal coordinate analysis (PCoA), determined by the Bray-Curtis and Euclidean distance matrices, was conducted to explore the difference in bacterial diversity between the control and test groups, and the results are shown in Figure 2A. There was a large distance between the control and test group, while a small distance between the samples fermented for 7 and 35 days of the test group was found. The difference between groups was calculated to assess whether it was bigger than the difference within groups using analysis of similarities (ANOSIM), and it was discovered that the former was larger than the latter (Figure 2B). With operational taxonomic units (OTUs) identified at 97% sequence similarity, clustering was carried out to investigate the number of species in each group. A total of 87 OTUs were found at the genus level, as shown by the Venn diagram (Figure 2C). Totals of 83 and 68 OTUs were found in the control and test groups, representing 95.40% and 78.16% of the total OTUs, respectively. Linear discriminant analysis effect size (LEfSe) was conducted to find the bacteria with significant differences in relative abundance between control and test groups, and the result is shown in Figure 2D. The microbial biomarker in the test group was _Tetragonococcus_, while the microbial biomarkers found in the control group were _Marinilatchillus_, _Lentiobacillus_, and _Pseudoalteromonas_. The inoculation of _T. muriaticus_ might have caused a significant change in the microbial diversity in the shrimp paste.