Bioactive compounds and molecular diversity of endophytic actinobacteria isolated from desert plants

With the aim to find endophytic actinomycetes that synthesize bioactive compounds over 800 strains were isolated from 53 desert plants of the Gobi-Sumber, Umnugobi, Dundgobi, Dornogobi, Bayankhongor, and Gobi-Altai provinces of Mongolia. The HPLC study of strains with high anti-quorum sensing and antibacterial activities revealed that they produced flavonoids and phenolic compounds. Molecular diversity evaluated with 16S rRNA gene sequences of 123 strains showed that they belonged to 12 genera: Streptomyces, Promicromonospora, Micromonospora, Streptosporangium, Kribbella, Pseudonocardia, Nocardia, Micromonospora, Saccharothrix, Friedmanniella, Actinocatenispora, and Geodermatophilus, the latter two genera were registered in Mongolia for the first time. Moreover, the genus Actinocatenispora was isolated from plants for the first time.

Diversity of Endophytic Actinomycetes Producing Indole-3- Acetic Acid and In vitro Evaluation of Plant Growth-promoting Activity on Brassica oleracea L.

The evaluation of endophytic actinomycetes diversity, growth-promoting strain effects on cauliflower seeds germination, and in vitro organogenesis are the objectives in this study. Moreover, 15 strains from 125 isolates were determined to produce indole-3- acetic acid (IAA), where majority was obtained from roots (66.67%), followed by from branches (26.67%) and leaves (6.67%). Specifically, Jatropha sp. is a plant species with the most endophytic actinomycetes content compared to others. In addition, all endophytic Streptomyces strains were screened based on IAA production ability in vitro on yeast extract–malt extract broth (YMG) broth medium. The results showed the tendency for one strain with code Streptomyces sp. KMR-1E to generate a maximum IAA isolate from Cinnamomun sp. plant. Furthermore, the molecular taxonomy and phylogenetic analysis were recreated from 16S rRNA gene sequences, which attributed the KMR- 1E to genus Streptomyces. Meanwhile, plant growth promotion was evaluated under in vitro condition. This exposed the individual ability to enhance the shoot and root length of cauliflowers. The untreated cultures with a strain free agar block was used as control.

Molecular profiling and anti-infective potency of endophytic actinomycetes inhabiting Madhuca insignis Radlk., from Western Ghats of India

Background Endophytic actinomycetes are well known for their diverse bioactive entities and considered as an important source for drug development research. Results We isolated and identified four potential endophytic Streptomyces species, i.e., Streptomyces misionensis MI22, Streptomyces roietensis MI24, Streptomyces glaucescens MI29, and Streptomyces sp. MI04 inhabiting Madhuca insignis by its characteristic morphological features and 16S rRNA gene sequence analysis. S. misionensis MI22 exhibits a broad spectrum of anti-microbial activity against methicillin-resistant Staphylococcus aureus (25.00 ± 1.00 mm) followed by Bacillus subtilis (23.66 ± 0.57 mm), Escherichia coli (22.00 ± 0.00 mm), and Candida albicans (18.00 ± 0.00 mm). Minimum inhibitory concentrations of the ethyl acetate fraction of S. misionensis MI22 against test pathogens were ranged from 25 to 100 μg/mL. Indeed, strain MI22 also exhibited significant anti-proliferative activity against HeLa cell line with IC50 value 98 μg/mL and showed no cytotoxicity effect to the normal human embryonic kidney cell line in the MTT assay. The anti-microbial metabolites from strain MI22 were detected at Rf 0.55 as depicted by the inhibition zone on the intensive band in TLC-bioautography assay. Conclusion The study indicates that, anti-microbial metabolites of these endophytic Streptomyces species, especially S. misionensis MI22 as a prolific source to discover novel bioactive metabolites to combat multidrug-resistant pathogens.

Isolation and structure elucidation of phenazine derivative from Streptomyces sp. strain UICC B-92 isolated from Neesia altissima (Malvaceae)

Background and Objectives: Endophytic actinomycetes have been known as a promising source for new antibiotics discov- ery against susceptible and resistant forms of pathogenic microorganisms. This study was aimed at determining antibacterial compound from Streptomyces sp. strain B-92 isolated from a medicinal plant Neesia altissima. Materials and Methods: Streptomyces sp. strain UICC B-92 was endophytic actinomycetes of N. altissima that obtained from Universitas Indonesia Culture Collection (UICC). Isolation and determination of bioactive compound were carried out using thin layer chromatography (TLC), nuclear magnetic resonance spectroscopy (NMR), and liquid chromatography mass spectrometry (LC-MS) analyses. An in vitro antibacterial assay of pure bioactive compound from the endophytic actinomycetes strain was performed against Bacillus cereus strain ATCC 10876, Escherichia coli strain ATCC 25922, Salmonella typhimurium strain ATCC 25241, Shigella flexneri strain ATCC 12022 and Staphylococcus aureus strain ATCC 25923. Results: The bioactive compound was identified as 4-((3S,4R,5S)-3,4,5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H- pyran-2-yloxy) phenazine-1-carboxylic acid. In vitro antimicrobial assay showed that bioactive compound of Streptomyces sp. strain UICC B-92 exhibited antagonistic activities against two Gram-positive bacteria, viz, B. cereus strain ATCC 10876 and S. aureus strain ATCC 25923. Conclusion: The findings of this research showed that, bioactive compound of Streptomyces sp. strain UICC B-92 is sug- gested a new compound based on glycoside structure and its position.