## 3 Results  
The bacterial 16S rRNA abundance, as determined by qPCR, increased significantly by nearly threefold in +Compost soil compared with \(-\)Compost soil (Figure 1a). Analysis of sequence data yielded on average 782 operational taxonomic units (OTUs) for \(-\)Compost and 750 OTUs for \(+\)Compost, which were not significantly different. Additionally, no significant differences for diversity and richness estimates were observed between the treatments (Table 1). A 98% coverage from Good's coverage estimator and rarefaction curve (Figure S1) showed that sampling was sufficient to estimate those indices. Principal coordinate analysis (PCoA), performed to estimate the effects of studied treatments on bacterial community composition, showed differences in ordination patterns of the treatments with PC1 explaining 28% of variance and PC2 explaining 22% of variance (Figure 1b). Figure 1: (a) The 16S rRNA copy numbers of soil bacterial communities estimated by qPCR. (b) The principal coordinate analysis (PCoA) showing the clustering of bacterial communities between soil samples. Values for 16S rRNA data are plotted with mean; error bars indicate standard errors; different letters on plot mean significant difference (\(p\) < 0.05) between treatments according to [PERSON]’s test. At taxonomic levels, the sequences from the soils were annotated to 56 different phyla, of which the 20 most abundant phyla are represented in Figure 2a. Proteobacteria were the most abundant bacterial phylum in both the studied soil groups, followed by Chloroflexi, Actinobacteria, Verrucomicrobia, Firmicutes, Bacteroidetes, Nitrospirae, uncultured-ODI, Gemmatimonadetes, uncultured-TM7, Cyanobacteria, Chlorobi, Elusimicroiba, Fibroketeres, Chlamydia, Spirochaetes, uncultured-WS3, and Armatimonadetes. Of all phyla, the abundance of Chloroflexi and Firmicutes varied significantly with Chloroflexi significantly abundant in \(-\)Compost soils while Firmicutes significantly dominating +Compost soils. At the bacterial order level (Figure 2b), Actinomycetes were the most abundant, followed by other groups. However, Rhiziales and Clostridiales were significantly abundant in \(+\)Compost, whereas the abundance of uncultured-SJA-15 increased significantly in \(-\)Compost soils. LefSe analysis (Figure 3) demonstrated that \(-\)Compost soils had significantly higher abundance of the phylum Chloroflexi and their related class Anaerobic and the phylum Acidobacteria and their related order Acidobacterialies compared with \(-\)Compost soils. On the other hand, \(+\)Compost soils had higher abundance of Actinobacteria along with the family Microcaceae and genus _Arthobacter_, and Firmicutes along with the class Bacilli and order Bacillales. Additionally, abundance of the class Alphaproteobacteria, their related order Rhiziales, family Hyphomicrobiaceae, and genus _Rhodoplanes_ increased significantly in \(+\)Compost soils compared with \(-\)Compost soils. The predicted abundance of genes encoding enzymes related to plant growth promotion, development, and fatty acid biosynthesis was significantly increased in \(+\)Compost soils when compared with \(-\)Compost soils (Figure 4). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Treatment** & \begin{tabular}{c} **No. of** \\ **Sequences** \\ \end{tabular} & \
\begin{tabular}{c} **Goods** \\ **Coverage (\%)** \\ \end{tabular} & **No. of OTUs** & **Chao** &
\begin{tabular}{c} **Shannon’s** \\ **Index** \\ \end{tabular} \\ \hline \(-\)Compost & 6567 & 98.6 & 782 \(\pm\) 6.71 1  & 816 \(\pm\) 8.2  & 6.02 \(\pm\) 0.02  \\ \(+\)Compost & 6567 & 98.8 & 750 \(\pm\) 13.5  & 775 \(\pm\) 15  & 5.98 \(\pm\) 0.01  \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary data for 165 rRNA sequencing results and \(\alpha\)-diversity of the soil samples. Figure 2: _Cont._  
Figure 3: The significantly different taxa of bacteria between two soil samples depicted by linear discriminant analysis effect size (LEfSe) method.