Diversity and Applications of Endophytic Actinobacteria of Plants in Special and Other Ecological Niches

Abstract

Actinobacteria are wide spread in nature and represent the largest taxonomic group within the domain Bacteria. They are abundant in soil and have been extensively explored for their therapeutic applications. This versatile group of bacteria has adapted to diverse ecological habitats, which has drawn considerable attention of the scientific community in recent times as it has opened up new possibilities for novel metabolites that may help in solving some of the most challenging problems of the day, for example, novel drugs for drug-resistant human pathogens, affordable means to maintain ecological balance in various habitats, and alternative practices for sustainable agriculture. Traditionally, free dwelling soil actinobacteria have been the subject of intensive research. Of late, symbiotic actinobacteria residing as endophytes within the plant tissues have generated immense interest as potential source of novel compounds, which may find applications in medicine, agriculture, and environment. In the light of these possibilities, this review focuses on the diversity of endophytic actinobacteria isolated from the plants of extreme habitats and specific ecological niches. Furthermore, an attempt has been made to assign chemical class to the compounds obtained from endophytic actinobacteria. Potential therapeutic applications of these compounds and the utility of endophytic actinobacteria in agriculture and environment are discussed.

Phylogenetic and Functional Characterization of Culturable Endophytic Actinobacteria Associated With Camellia spp. for Growth Promotion in Commercial Tea Cultivars

“…As in previous studies, both Streptomyces and non-Streptomyces spp. were reported as IAA producers and within a similar range (Nimnoi et al, 2010;Shutsrirung et al, 2013;Singh and Dubey, 2018). Phosphorus is a major micronutrient responsible for many functional processes and phosphate solubilizing bacteria (PSB) can increase the availability of phosphorus for the plants.…”

“…In previous studies, many Streptomyces sp. were reported for the synthesis of antifungal metabolites as well as some reports on rare actinobacteria for antimicrobial metabolite production are reported (El-Tarabily et al, 2010;Palaniyandi et al, 2013;Singh and Dubey, 2018). Endophytic actinobacteria with positive chitinase, NRPS, PKS-1 gene showed antagonistic activity and protected plants against plant phytopathogens (Passari et al, 2016b).…”

“…Endophytes are microbes found within various plant tissues, including roots, stems, leaf, flower, fruits, seeds, pollen in a symbiotic relationship without causing any apparent harm (Zhang et al, 2019). Endophytic actinobacteria are recognized as potential agents for their PGP effects and their role in nutrient uptake in host plants by producing biologically active secondary metabolites that enhance the fitness and resilience of the plants against environmental stress (Dinesh et al, 2017;Singh and Dubey, 2018). Endophytic actinobacteria have drawn a significant interest in the recent years for their ability to produce bioactive secondary metabolites with diverse function (Sathya et al, 2017).…”

Phyllospheric Microbiomes: Diversity, Ecological Significance, and Biotechnological Applications

“…They are soil-inhabiting saprophytic microbes and have been extensively studied for their therapeutic secondary metabolites. This versatile group of gram-positive bacteria has adapted to diverse environments including the phyllosphere of the plant (Singh et al 2018). Some actinobacteria form symbiotic association residing in plant tissues have generated (Coombs and Franco 2003;Thamchaipenet et al 2010;Chen et al 2011;Xie et al 2011;Yadav 2017;Yadav and Yadav 2018).…”

All small things considered: the diversity of fungi, bacteria and oomycota isolated from the seagrass,Zostera marina

“…This includes several Actinomycetes (Streptomyces sp., Rhodococcus sp. and Isoptericola) which are known to produce a variety of antibiotics and interesting secondary metabolites (Singh & Dubey, 2018) and members of the genus, Isoptericola, have been previously isolated as endophytes of mangrove plants . We also isolated a Phyllobacterium sp.…”