Genome-guided Investigation of Antibiotic Substances produced by Allosalinactinospora lopnorensis CA15-2(T) from Lop Nor region, China

Anti-inflammatory, anti-infectious and anti-cancer potential of marine algae and sponge: A review

Marine organisms are potentially a pretty good source of highly bioactive secondary metabolites that are best known for their anti-inflammation, anti-infection, and anti-cancer potential. The growing threat of bacterial resistance to synthetic antibiotics, is a potential source to screen terrestrial and marine natural organisms to discover promising anti-inflammatory and antimicrobial agents which can synergistically overcome the inflammatory and infectious disases. Algae and sponge have been studied enormously to evaluate their medicinal potential to fix variety of diseases, especially inflammation, infections, cancers, and diabetes. Cytarabine is the first isolated biomolecule from marine organism which was successfully practiced in clinical setup as chemotherapeutic agent against xylogenous leukemia both in acute and chronic conditions. This discovery opened the horizon for systematic evaluation of broad range of human disorders. This review is designed to look into the literature reported on anti-inflammatory, anti-infectious, and anti-cancerous potential of algae and sponge to refine the isolated compounds for value addition process.

Biocontrol potential and antifungal mechanism of a novel Streptomyces sichuanensis against Fusarium oxysporum f. sp. cubense tropical race 4 in vitro and in vivo

Most commercial banana cultivars are highly susceptible to Fusarium wilt caused by soilborne fungus Fusarium oxysporum f. sp. cubense (Foc), especially tropical race 4 (TR4). Biological control using antagonistic microorganism has been considered as an alternative method to fungicide. Our previous study showed that Streptomyces sp. SCA3-4 ^T had a broad-spectrum antifungal activity from the rhizosphere soil of Opuntia stricta in a dry hot valley. Here, the sequenced genome of strain SCA3-4 ^T contained 6614 predicted genes with 72.38% of G + C content. A polymorphic tree was constructed using the multilocus sequence analysis (MLSA) of five house-keeping gene alleles (atpD, gyrB, recA, rpoB, and trpB). Strain SCA3-4 ^T formed a distinct clade with Streptomyces mobaraensis NBRC 13819 ^T with 71% of bootstrap. Average nucleotide identity (ANI) values between genomes of strain SCA3-4 ^T and S. mobaraensis NBRC 13819 ^T was 85.83% below 95-96% of the novel species threshold, and named after Streptomyces sichuanensis sp. nov. The type strain is SCA3-4 ^T (= GDMCC 4.214 ^T = JCM 34964 ^T). Genomic analysis revealed that strain SCA3-4 ^T contained 36 known biosynthetic gene clusters of secondary metabolites. Antifungal activity of strain SCA3-4 ^T was closely associated with the production of siderophore and its extracts induced the apoptosis of Foc TR4 cells. A total of 12 potential antifungal metabolites including terpenoids, esters, acid, macrolides etc. were obtained by the gas chromatography-mass spectrometry (GC-MS). Greenhouse experiment indicated that strain SCA3-4 ^T could significantly inhibit infection of Foc TR4 in the roots and corms of banana seedlings and reduce disease index. Therefore, strain SCA3-4 ^T is an important microbial resource for exploring novel natural compounds and developing biopesticides to manage Foc TR4. KEY POINTS: • Strain SCA3-4 ^T was identified as a novel species of Streptomyces. • Siderophore participates in the antifungal regulation. • Secondary metabolites of strain SCA3-4 ^T improves the plant resistance to Foc TR4.

Exploring the Potential of Antibiotic Production From Rare Actinobacteria by Whole-Genome Sequencing and Guided MS/MS Analysis

Actinobacteria are well recognized for their production of structurally diverse bioactive secondary metabolites, but the rare actinobacterial genera have been underexploited for such potential. To search for new sources of active compounds, an experiment combining genomic analysis and tandem mass spectrometry (MS/MS) screening was designed to isolate and characterize actinobacterial strains from a mangrove environment in Macau. Fourteen actinobacterial strains were isolated from the collected samples. Partial 16S sequences indicated that they were from six genera, including Brevibacterium, Curtobacterium, Kineococcus, Micromonospora, Mycobacterium, and Streptomyces. The isolate sp.01 showing 99.28% sequence similarity with a reference rare actinobacterial species Micromonospora aurantiaca ATCC 27029T was selected for whole genome sequencing. Organization of its gene clusters for secondary metabolite biosynthesis revealed 21 clusters encoded to antibiotic production, which is higher than other Micromonospora species. Of the genome-predicted antibiotics, kanamycin was found through guided MS/MS analysis producible by the M. aurantiaca strain for the first time. The present study highlighted that genomic analysis combined with MS/MS screening is a promising method to discover potential of antibiotic production from rare actinobacteria.

Marine Natural Products: A Source of Novel Anticancer Drugs

Cancer remains one of the most lethal diseases worldwide. There is an urgent need for new drugs with novel modes of action and thus considerable research has been conducted for new anticancer drugs from natural sources, especially plants, microbes and marine organisms. Marine populations represent reservoirs of novel bioactive metabolites with diverse groups of chemical structures. This review highlights the impact of marine organisms, with particular emphasis on marine plants, algae, bacteria, actinomycetes, fungi, sponges and soft corals. Anti-cancer effects of marine natural products in in vitro and in vivo studies were first introduced; their activity in the prevention of tumor formation and the related compound-induced apoptosis and cytotoxicities were tackled. The possible molecular mechanisms behind the biological effects are also presented. The review highlights the diversity of marine organisms, novel chemical structures, and chemical property space. Finally, therapeutic strategies and the present use of marine-derived components, its future direction and limitations are discussed.

Marine Natural Products: A Source of Novel Anticancer Drugs

Cancer remains one of the most lethal diseases worldwide. There is an urgent need for new drugs with novel modes of action and thus considerable research has been conducted for new anticancer drugs from natural sources, especially plants, microbes and marine organisms. Marine populations represent reservoirs of novel bioactive metabolites with diverse groups of chemical structures. This review highlights the impact of marine organisms, with particular emphasis on marine plants, algae, bacteria, actinomycetes, fungi, sponges and soft corals. Anti-cancer effects of marine natural products in in vitro and in vivo studies were first introduced; their activity in the prevention of tumor formation and the related compound-induced apoptosis and cytotoxicities were tackled. The possible molecular mechanisms behind the biological effects are also presented. The review highlights the diversity of marine organisms, novel chemical structures, and chemical property space. Finally, therapeutic strategies and the present use of marine-derived components, its future direction and limitations are discussed.

Biosynthetic Potential of Bioactive Streptomycetes Isolated From Arid Region of the Thar Desert, Rajasthan (India)

Acquisition of Actinobacteria, especially Streptomyces from previously underexplored habitats and the exploration of their biosynthetic potential have gained much attention in the rejuvenated antibiotics search programs. Herein, we isolated some Streptomyces strains, from an arid region of the Great Indian Thar Desert, which possess an ability to produce novel bioactive compounds. Twenty-one morphologically distinctive strains differing in their aerial and substrate mycelium were isolated by employing a stamping method. Among them, 12 strains were identified by a two-level antimicrobial screening method, exerting antimicrobial effects against a panel of indicator strains including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus species. Based on their potent antimicrobial activity, four isolates were further explored by 16S rRNA gene-based identification, genetic screening, and metabolomic analysis; and it was found that these strains belong to the genus Streptomyces. The selected strains were found to have polyketide synthase and non-ribosomal peptide synthetase systems. In addition, extracellular metabolomic screening revealed that the isolates produced analogs of doxorubicinol, pyrromycin, erythromycin, and 6-13 other putative novel metabolites. These results demonstrate the significance of Streptomyces inhabiting the arid region of Thar Desert, suggesting that similar arid environments can be considered as the reservoirs of novel Streptomyces strains that could have biotechnological significance.

Intertidal marine sediment harbours Actinobacteria with promising bioactive and biosynthetic potential

Actinobacteria are the major source of bioactive natural products that find their value in research and drug discovery programmes. Antimicrobial resistance and the resulting high demand for novel antibiotics underscore the need for exploring novel sources of these bacteria endowed with biosynthetic potential. Intertidal ecosystems endure regular periods of immersion and emersion, and represent an untapped source of Actinobacteria. In this study, we studied the diversity and biosynthetic potential of cultivable Actinobacteria from intertidal sediments of Diu Island in the Arabian Sea. A total of 148 Actinobacteria were selectively isolated using a stamping method with eight isolation media. Isolates were grouped into OTUs based on their 16S rRNA gene sequence, and categorized within actinobacterial families such as Glycomycetaceae, Micromonosporaceae, Nocardiaceae, Nocardiopsaceae, Pseudonocardiaceae, Streptomycetaceae, and Thermomonosporaceae. The biosynthetic potential of the Actinobacteria, necessary for secondary metabolite biosynthesis, was screened and confirmed by extensive fingerprinting approaches based on genes coding for polyketide synthases and nonribosomal peptide synthetases. The observed biosynthetic potential was correlated with the antibacterial activity exhibited by these isolates in laboratory conditions. Ultimately, the results demonstrate that intertidal sediment is a rich source of diverse cultivable Actinobacteria with high potential to synthesize novel bioactive compounds in their genomes.