## 3 Results and Discussion
### 16S rRNA High-Throughput Sequencing Analysis
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample*** & **No. of Reads** & **No. of OTUs** & **Chao1 Index** & **Shannon Index** & **Simpson Index** & **No. of Genera** \\ \hline D0 & 82,359 & 9915 & 53,904 & 7.32 & 0.96 & 76 \\ C3 & 150,114 & 18,824 & 126,204 & 6.03 & 0.80 & 31 \\ C6 & 144,592 & 18,146 & 132,612 & 6.05 & 0.86 & 21 \\ TP6 & 57,660 & 7586 & 46,409 & 6.80 & 0.93 & 70 \\ TP12 & 123,255 & 10,044 & 67,274 & 3.05 & 0.40 & 11 \\ Mean & 111,596 & 12,903 & 85,280 & 5.85 & 0.79 & 42 \\ \(\pm\) SD & \(\pm\) 40,224 & \(\pm\) 5194 & \(\pm\) 41,032 & \(\pm\) 1.66 & \(\pm\) 0.23 & \(\pm\) 29 \\ \hline \hline \end{tabular}  
* D0 indicates fresh, crisp grass carp fillets prior to any treatment. C3 and C6 indicate the fillet samples that were treated with distilled water and stored for 3 and 6 days, respectively. TP6 and TP12 indicate the fillet samples that were treated with tea polyphenols and stored for 6 and 12 days, respectively.  
\end{table} 
Table 1: Crisp grass carp sample information, microbial diversity, and sequence analysis. Figure 3: Principal coordinate analysis of the crisp grass carp fillet bacterial communities based on (**a**) weighted and (**b**) unweighted UniFrac metrics of samples during storage at 4 \({}^{\circ}\)C.  
Seven bacterial phyla were identified in the fresh fillets (D0), consisting of Actinobacteria, Bacteroidetes, Firmicutes, Fusobacteria, Proteobacteria, TM7, and Therni (Figure 4a). In the fresh fillet, the predominant phyla were Proteobacteria and Bacteroidetes (accounting for 50.1% and 32.3% of the bacteria, respectively). By 6 th day, the Proteobacteria increased significantly to 97.8% in the fillet treated with distilled water, as compared to 99.3% in the fillet treated with tea polyphenols by the end of 12 days. In contrast, Bacteroidetes declined sharply to 0.4% in the fillet treated with distilled water and to 0.1% in fillet treated with the tea polyphenols; these findings are consistent with previously published studies [12]. Interestingly, the relative abundance of Fusobacteria, accounting for 8.1% of the bacteria in the fresh fillets, was higher in our study than that reported in previous studies, which disappeared by the end of the storage period [12]. The dynamics of the bacterial community (at the genus level) during the cold storage at 4 \({}^{\circ}\)C, are displayed in Figure 4b. By the end of the cold storage, seventy six genera of bacteria were identified in the fresh fillets, which was significantly higher than the number of genera identified in the samples treated with tea polyphenols (21 genera) or distilled water (11 genera) (Table 1); the principal genera identified in samples included _Acinetobacter_, _Flavobacterium_, _Sphingomonas_, _Clrysobacterium_, _Enhydrobacter_, and _Cetobacterium_, constituting for 17.9, 15.6, 11.8, 9.5, 8.6, and 7.5% of bacterial population in fresh fillets, respectively (Figure 4b). _Acinetobacter_ commonly found in natural waters was the predominant bacteria not only in the crisp grass carp fillets of this study and those reported previously [12] but also in grass carp (_Cetenopharynxgodon idellus_) [20], common carp (_Cyprinus carpio_) [21] and silver carp (_Hypophthalmichthys molitrix_) [7], suggesting that _Acinetobacter_ could be the resident flora in this fish. After 3 days, this bacterial genus decreased slightly to 16.1% in the distilled water treated fillets during the 4 \({}^{\circ}\)C storage and declined to 10.3% after 6 days. Figure 4: Relative abundance of the bacterial phyla (**a**) and genera (**b**) in crisp grass carp fillets during chilled storage at 4 \({}^{\circ}\)C. Only genera \(\geq\) 1% of the total relative abundance of the samples are shown. In contrast, its abundance decreased significantly to 8.7% after 6 days in the fillet treated with tea polyphenols and then decreased sharply to 0.6% after 12 days. These results indicated tea polyphenols inhibited the growth of _Acinetobacter_, which was consistent with the results of [PERSON] et al., [7].