Characterization of growth promoting bacterial endophytes isolated from Artemisia annua L.

The highly diverse nature of plant microbiota is indicative of many ecological roles of this group of microorganisms. For important medicinal plants such as Artemisia annua L (Family Asteraceae), there can be numerous functional attributes of the associated bacterial endophytes, but the diversity and functions of such endophytes remain widely unknown. To understand their potential functional diversity, we isolated endophytic bacteria associated with the plant from different plant parts including leaves, stems, and roots. Bacterial community of the leaves showed more diversity than those of the stems and the roots. Bacterial isolates were screened in vitro for various plant growth promoting attributes including Indole acetic acid (IAA), 1-aminocyclopropane-1-carboxylate (ACC) deaminase production, and nitrogen fixation. Ninety five percent of the isolates were able to produce IAA, while 7.5% produced ACC deaminase, and 15% were able to fix nitrogen. Based on their potential plant growth promoting attributes, 25 bacterial isolates of 16 genera belonging to four phyla were identified. Proteobacteria (36%) and Firmicutes (36%) were the most predominant isolated bacteria, followed by Actinobacteria (24%) and Bacteroidetes (4%). The most promising isolates were selected for the investigation of their ability to enhance seed germination. We observed that the treatment with isolates AAR80 Bacillus selenatarsenatis and AAL56 Achromobacter xylosoxidans increased germination percentage of inoculated seeds. Moreover, (48%) of the isolates showed antimicrobial activity upon testing against indicator microorganisms. This study revealed that endophytic bacteria isolated from A. annua L have dual potential to be used as growth promoters and antimicrobial agents.