Bioactivity of medicinal plant and insect associated microbiota

Nikena Khwairakpam


The worsening global challenges such as climate change and increased population are leading to agricultural stress and antimicrobial resistance (AMR), necessitating the search for novel sources of microbial diversity [1]. Microbial diversity remains an unparalleled source of bioactive molecules and, of late, symbiotic microbes associated with plants and insects have been proposed as promising sources [3]. The present study was targeted at accessing selected ethno-medicinal plants and insects in Manipur, India for isolating bacterial symbionts and screening their promising bioactivities.
As soil microbiota have been overexploited for bioactive molecules, bioprospecting of endophytic microorganisms inhabiting plants especially medicinal plants and symbiotic microbes associated with insects holds great promise.
A total of 321 bacterial strains were isolated from 6 ethnomedicinal plant (Blumeopsis flava, Pholidota graffithii, Alocasia indica, Vangueria spinosa Linn., Curcuma aromatica Salisb, Celtis timorensis Linn) and 6 insect samples (putatively identified as Oecophylla smaragdina, Oxya sp., Apis cerana, Thysia wallichi tonkinensis, Crematogaster sp., and an as-yet unidentified black ant species). Thirty-eight (38) of the 321 bacterial symbiont isolates showed antibacterial activity against one or more of the 3 test organisms (Micrococcus luteus, MTCC 106; Bacillus subtilis, MTCC 121 and Escherichia coli, MTCC 739). Thirty-seven (37) isolates showed biocontrol activity against one or more of the 5 fungal test organisms (Rhizoctonia solani, MTCC 4633, Pyricularia oryzae, MTCC 1477, Fusarium oxysporum MTCC 284, Aspergillus niger, MTCC 432, and Curvularia oryzae, MTCC 2605). All the 67 bioactive bacterial symbiont isolates were screened for Plant Growth Promoting (PGP) traits, of which 19 were found positive for phosphate solubilization and 11 for siderophore production. 12 isolates have been selected for characterization as they were found to have broad spectrum antibacterial or antifungal activity. Interestingly, 2 insect associated bacterial isolates (D4IN-8 and D3N-1) showed both phosphate solubilization and siderophore production traits. Further screening of these isolates for other PGP traits are currently underway. The study indicates that bacteria associated with ethnomedicinal plants and insects in Manipur have potential antimicrobial activities and can be exploited as biocontrol and plant growth promoting (PGP) agents for agricultural applications and pharmaceutical use.

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