Characterization of endophytic bacteria, Solibacillus silvestris DDBU6 and Kocuriaassamensis DDBU9 isolated from the leaves of a medicinal plant, Phlogacanthusthyrsiformis

Abstract

Endophyte’s symbiotic association with host plants can be immensely valuable to agriculture because it promotes plants's growth and development. Endophytic bacteria present in medicinal plants play a highly essential role in the fields of pharmacology as well as agriculture, since therapeutic plants themselves are reservoirs for a variety of significant bioactive substances. However, the study of the endophytic bacteria presents in the medicinal plant, Phlogacanthusthyrsiformis, remains unknown. The primary goal of this research is to isolate, characterize, and molecular identification of endophytic bacteria present in the leaves of P. thyrsiformis. Two endophytic bacteria were isolated from theleaves: Solibacillus silvestrisDDBU6 (PTL-1) and KocuriaassamensisDDBU9 (PTL-2). In this study, K. assamensis was identified as an endophytic bacterium for the first time. Gram staining revealed that both leaf isolates were Gram-positive. In biochemical tests, both isolates tested negative for indole production but positive for citrate utilization and catalase activity PTL-1 and PTL-2 tested negative for oxidase test. S. silvestris and K. assamensiswere able to tolerate 5% NaCl. These bacteria, under conditions of salt stress, hold potential to support plant growth. Moreover, in plant growth promotion assays, both the isolates exhibited positive results for ammonia production, negative for phosphate solubilization. For IAA production ability, highest production was shown by PTL-1 (81 ± 1.24 µg/ml) followed by PTL-2 (45 ± 0.47 µg/ml). All isolates showed promise as a viable endophytic bacterium for application in agriculture, possibly helping to produce ecologically friendly biofertilizers due to its positive results for some plant growth promotion activities and its tolerance of high salt concentrations.