Mangroves are woody plants located in tropical and subtropical intertidal coastal regions. The mangrove ecosystem is becoming a hot spot for natural product discovery and bioactivity survey. Diverse mangrove actinomycetes as promising and productive sources are worth being explored and uncovered. At the time of writing, we report 73 novel compounds and 49 known compounds isolated from mangrove actinomycetes including alkaloids, benzene derivatives, cyclopentenone derivatives, dilactones, macrolides, 2-pyranones and sesquiterpenes. Attractive structures such as salinosporamides, xiamycins and novel indolocarbazoles are highlighted. Many exciting compounds have been proven as potential new antibiotics, antitumor and antiviral agents, anti-fibrotic agents and antioxidants. Furthermore, some of their biosynthetic pathways have also been revealed. This review is an attempt to consolidate and summarize the past and the latest studies on mangrove actinomycetes natural product discovery and to draw attention to their immense potential as novel and bioactive compounds for marine drugs discovery.

https://www.mdpi.com/1660-3397/12/5/2590/pdf

Natural Products from Mangrove Actinomycetes

/pdf/endophytic-actinomycetes-as-emerging-source-for-therapeutic-50oxz05og2.pdf

Endophytic Actinomycetes as Emerging Source for Therapeutic Compounds

Activity and diversity of culturableStreptomycesisolated from marine sediments of sea areas of Dalian

Halophytes are associated with the intertidal forest ecosystem of Saudi Arabia and seemingly have an immense potential for yielding useful and important natural products. In this study we have aimed to isolate and characterize the endophytic and rhizospheric bacterial communities from the halophyte, Salsola imbricata, In addition these bacterial strains were identified and selected strains were further studied for bioactive secondary metabolites. At least 168 rhizspheric and endophytic bacteria were isolated and of these 22 were active antagonists against the oomycetous fungal plant pathogens, Phytophthora capsici and Pythium ultimum. Active cultures were mainly identified with molecular techniques (16S r DNA) and this revealed 95.7-100% sequence similarities with relevant type strains. These microorgansims were grouped into four major classes: Actinobacteria, Firmicutes, β-Proteobacteria, and γ-Proteobacteria. Production of fungal cell wall lytic enzymes was detected mostly in members of Actinobacteria and Firmicutes. PCR screening for type I polyketide synthases (PKS-I), type II polyketide synthases (PKS-II) and nonribosomal peptide synthetases (NRPS) revealed 13 of the 22 strains (59%) were positive for at least one of these important biosynthetic genes that are known to be involved in the synthesis of important antibiotics. Four bacterial strains of Actinobacteria with potential antagonistic activity including two rhizobacteria, EA52 (Nocardiopsis sp.), EA58 (Pseudonocardia sp.) and two endophytic bacteria Streptomyces sp. (EA65) and Streptomyces sp. (EA67) were selected for secondary metabolite analyses using LC-MS. As a result, the presence of different bioactive compounds in the culture extracts was detected some of which are already reported for their diverse biological activities including antibiotics such as Sulfamethoxypyridazine, Sulfamerazine, and Dimetridazole. In conclusion, this study provides an insight into antagonistic bacterial population especially the Actinobacteria from S. imbricata, producing antifungal metabolites of medical significance and characterized taxonomically in future.

/pdf/microbial-flora-associated-with-the-halophyte-salsola-1n8zmoceqf.pdf

Microbial Flora Associated with the Halophyte–Salsola imbricate and Its Biotechnical Potential

A total of 144 endophytic actinomycetes were isolated from roots, stems and leaves of Aegle marmelos (n=51), Murraya koenigii (n=35) and Syzygium cumini (n=58). Another 71 isolates (35 from Azadirachta indica, 36 from Emblica officinalis) were procured from the Department of Microbiology, PAU. Ethyl acetate extracts of the culture supernatants from starch casein broth were prepared in vacuo (-130°C). A total of 25.58% extracts diffused the zone of clearance produced by alpha-amylase on starch agar medium. Out of these, 76.36 and 74.54% extracts inhibited the activity of α-amylase and α-glucosidase respectively. Out of 53 selected extracts, forty-one, forty-four, ten, twenty-four and forty-five extracts displayed scavenging of diphenyl-picryl-hydrazyl, hydroxyl, nitric, superoxide and linoleate free radicals respectively. Reduction of Fe 3+ to Fe 2+ was carried out by 88.67% extracts. Total phenol content was measured in terms of catechol and gallic acid equivalents/gram extract. On the basis of above findings, five potential extracts (AZS96, C-3, C-4, J-7 and J-8) were identified for further study. Their 1000μg/ml concentrations inhibited the diffusion of glucose across the semipermeable membrane within 24 hours. Michaelis-Menten kinetics indicated the modes of α-amylase and α-glucosidase inhibition to be pure or near competitive types. Liquid Chromatography-Mass Spectrometric analysis of C-4 P-α-Amy and J-7 P-α-Amy extracts confirmed the presence of phenolic compounds. In vitro inhibition against Staphylococcus aureus, Aspergillus fumigatus, Candida albicans, Klebsiella sp., Escherichia coli and Yersinia sp. was displayed by n=10, 4, 3, 3, 2, 1 isolates of S. cumini respectively. Out of these fifteen, eight different isolates were able to hydrolyze chitin and casein. Six of the isolates degraded carboxy-methyl-cellulose present in the culture medium. Thirteen, fourteen and fifteen of the S. cumini isolates exhibited amidase, amylase and lipase activity respectively. Staphylococcus aureus sample treated with J-17 culture supernatant subjected to Scanning Electron Microscopy, indicated swelling of cells and disruption of cell wall and cell membrane. Out of 66 isolates, 57.57% belonged to Streptomyces sp., followed by Micromonospora sp. (16.66%), Microbispora sp. (10.60%), Actinopolyspora sp. (9.09%), Saccharopolyspora sp. (4.54%) and Rhodoccocus sp. (1.51%). On the basis of 16S rDNA sequencing, AZS96 isolate was found to be Rhodococcus qingshengii strain BJC15-A38 and isolate C-3 showed similarity with Streptomyces koyangensis, strain B025.

Identification of bioactive metabolites from endophytic actinomycetes isolated from medicinal plants

OBJECTIVE In order to explore the diversity, antimicrobial activity and enzyme-producing activity of marine actinobacteria isolated from mangrove sediments in Indian Ocean. METHODS Eight sediments collected from mangrove sediments in Indian Ocean were treated by the plate dilution method and spread on 24 isolation media only containing sole carbon source for energy. Marine actinobacteria were isolated and identified by 16S rRNA gene sequence analysis. The antimicrobial activity and enzyme-producing activity of isolated strains were further detected by spot planting method. RESULTS In total 139 representative strains were selected from 521 isolates, and they were further sequenced and performed phylogenetic analysis based on their 16S rRNA gene sequences. There were 35 strains identified as potential novel species. Antimicrobial activity was detected in Bacillus subtilis, Candida albicans, Escherichia coli, Staphylococcus aureus, Aspergillus niger. Enzyme-producing activity for protease cellulase, amylase and esterase were 36.5%, 26.5%, 22.4% and 15.9%, respectively. CONCLUSION Diverse marine actinobacteria were discovered in mangrove sediment in Indian Ocean, which have antimicrobial and enzyme activity.

Diversity and bioactivities of culturable marine actinobacteria isolated from mangrove sediment in Indian Ocean

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Diversity and bioactivities of culturable marine actinobacteria isolated from mangrove sediment in Indian Ocean