Identification, Biocontrol and Plant Growth Promotion Potential of Endophytic Streptomyces sp. a13

Medicinal plants often harbour various endophytic actinomycetia, which are well known for their potent antimicrobial properties and plant growth-promoting traits. In this study, we isolated an endophytic actinomycetia, A13, from the leaves of tea clone P312 from the MEG Tea Estate, Meghalaya, India. The isolate A13 was identified as Streptomyces sp. A13 through whole genome sequencing (WGS) and 16S rRNA sequencing, showing 88% (ANI; Average Nucleotide Identity) and 99.78% sequence similarity with Streptomyces olivaceus. The strain A13 exhibited a prominent broad-spectrum antifungal activity against nine phytopathogens. It was observed that the ethyl acetate (EtAc) extract of A13 inhibits the spore germination rate of phytopathogen Nigrospora sphaerica (NSP) and also damages the fungal cell wall and cell structure. Additionally, the A13 strain exhibits several plant growth-promoting (PGP) traits, such as nitrogen fixation, ammonia production (4.7 µmol/ml), indole-acetic acid (IAA) production (8.91 µg/ml), siderophore production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity Gas chromatography mass spectrometry (GC-MS) analysis revealed that Phenol, 3,5-bis(1,1-dimethylethyl) was found to be the major chemical constituent in the EtAc extract of the A13 strain, accounting for 50.15% of the area percentage. Whole genome sequencing and subsequent genome analysis utilizing bioinformatics techniques such as Antibiotics & Secondary Metabolite Analysis SHell (antiSMASH) and Rapid Annotation using Subsystem Technology (RAST) revealed a wide array of biologically active secondary metabolite biosynthesis gene clusters (smBGCs) with different physiologically significant roles. These findings emphasize the potential of the A13 strain as a biocontrol agent with the capability to enhance plant growth and prevent diseases.