Diversity and antibacterial activity of endophytic bacteria associated with medicinal plant, Scrophularia striata

Abstract

To search endophytic bacteria diversity and evaluate their antibacterial activity, healthy medicinal plant of Scrophularia striata was chosen in this study. One hundred endophytic bacteria were isolated from surface-sterilized tissues (root, stem and leaf) of S. striata. Using sequence analysis targeting 16S rRNA gene, eight genera, including Agrococcus, Arthrobacter, Bacillus, Chryseobacterium, Delftia, Kocuria, Pseudomonas and Sphingomonas were identified. Antibacterial activity of endophytic bacteria was examined against some test bacteria, employing agar well diffusion method. Out of 31 endophytic bacterial isolates, 24(77.42%) isolates showed significant antimicrobial activity against Bacillus cereus, 17(54.84%) isolates exhibited maximum activity against Staphylococcus aureus, 14(45.16%) isolates against Escherichia coli and 5(16.13%) isolates showed positive activity against Proteus mirabilis.The results obtained in this study suggested that the medicinal plant, S. striatais is a potent source of endophytic bacteria with antibacterial activity and offers promise for discovery of more impressive biological compounds.

Keywords: 16S rRNA; Antibacterial activity; Diversity; Endophytes; Isolation.

Fig. 1

A representative selection of 16S rRNA gene PCR products obtained for endophytic bacterial isolates

Fig. 2

Phylogenetic tree for the comparative analysis of 16S rRNA gene sequences. This tree was constructed using the neighbor-joining method from aligned nucleotides. Bootstrap values (expressed as percentages of 1,000 replications) greater than 70.00% are shown at branch points. Bar: 5 substitutions per 100 nt positions