Diverse endophytic Streptomyces species with dynamic metabolites and their meritorious applications: a critical review

The strains of actinobacteria are unique as they lie between true fungi and bacteria and several of them were reported as endophytic actinobacteria as they were isolated from the inner regions of various plant parts and will enhance uptake of nutrients and improve defense against pathogens. Literature and scientific communications reported the relationship between the endophytes and plants, most of them concluded the association as commensalism. Remarkably, bioactive compounds from endophytic Streptomyces sp. were confirmed with various applications. A retrospective consolidation on the endophytic Streptomyces sp. and their metabolite application in day to day life is presented here. It was deduced that this group of the organism are a source for a wide range of bioactive compounds including anticancer agents, immune suppressor, plant growth promoters, anti-inflammatory agents, anti-tumor agents, enzymes and antimicrobial substances. These antimicrobial metabolites show broad-spectrum activity and are effective against bacteria and fungi. The mechanism of action of secondary metabolites from endophytes and its positive influence on the host plants are noted as involvement in deterrence, antifeedant activity, toxicity against common pests, and as enhancers for physical mechanisms such as water uptake and sunlight absorption, thus supporting the growth of host plants.