Isolation, Characterization, and Identification of Endophytic Bacteria from Curcuma Longa and Detection of Indole Acetic Acid and Gibberellic Acid Production

Abstract

Curcuma longa, commonly known as turmeric, is renowned for its medicinal properties, largely attributed to its bioactive compounds. Recent studies have focused on its endophytic bacteria, which reside within plant tissues and contribute to plant health and growth. This study aimed to isolate, characterize, and identify endophytic bacteria from Curcuma longa and evaluate their ability to produce the plant growth-promoting hormones indole acetic acid (IAA) and gibberellic acid (GA).Fifteen bacterial isolates were obtained from the roots, rhizomes, and leaves of Curcuma longa. These isolates were characterized based on their morphological and biochemical properties. Morphological characterization revealed diverse colony shapes, sizes, colors, and cell morphologies, including both Gram-positive and Gram-negative bacteria. Biochemical tests indicated varying abilities among the isolates to hydrolyze starch and gelatin, reduce nitrate, utilize citrate, and produce catalase and oxidase. Molecular identification using 16S rRNA gene sequencing identified the isolates as belonging to several genera, including Bacillus, Pseudomonas, Enterobacter, Stenotrophomonas, Acinetobacter, and Klebsiella. These genera are known for their plant growth-promoting traits, such as nutrient solubilization, biocontrol, and hormone production. The ability of these endophytes to produce IAA and GA was assessed using colorimetric assays and high-performance liquid chromatography (HPLC), respectively. Ten isolates produced IAA in concentrations ranging from 5 to 45 µg/mL, while eight isolates produced GA in concentrations ranging from 0.5 to 7 µg/mL. The highest levels of IAA and GA were observed in isolates identified as Bacillus sp. and Pseudomonas sp., respectively. Statistical analysis confirmed significant differences in hormone production among the isolates (p < 0.05). The diverse endophytic community and their capacity for hormone production highlight the potential of these bacteria as biofertilizers and biostimulants. These findings suggest that endophytic bacteria from Curcuma longa can be harnessed to promote sustainable agricultural practices by enhancing crop growth and productivity.This study advances our understanding of the beneficial roles of endophytic bacteria in medicinal plants, providing a foundation for the development of bio-based agricultural inputs that support sustainable crop production. Further research and field trials are necessary to fully explore the practical applications of these endophytes in agriculture.