*3.1. Isolation and Identification of the Endophytic Bacterium*

Endophytic bacteria live inside of plants without causing harm to the host plant [24]. In our study, we obtained a total of 17 endophytic bacterial isolates from the interior of onion leaves. One isolate, namely, H3 was selected based on its ability in the biosynthesis of AgNPs. This isolate was subjected to molecular identification. Partial 16S rRNA gene sequence analysis revealed that the selected isolate was belonging to the genus of *Bacillus* (Figure 1), and subjected to GenBank under accession number MN611116.

**Figure 1.** Phylogenetic tree of endophytic bacterium *B. endophyticus* strain H3 isolated from onion leaves in the seedling stage constructed by using 16S rRNA gene sequences. Bootstrap analysis (1000 replicates) for node values greater than 50% are given. Bar 0.02 substitutions per nucleotide position.
