Draft Genome Sequence of Bacillus sp. Strain M21, Isolated from the Arid Area of Matmata, Tunisia.

Bacillus sp. strain M21 was isolated from an environmental sample. In antibacterial screenings, the strain inhibited growth of Gram-positive and Gram-negative test strains. The genome was assembled into 69 contigs with a total size of 5.178 Mb. The strain contains at least nine biosynthetic gene clusters for the production of specialized metabolites.

The Potential of Indonesian Heterobranchs Found around Bunaken Island for the Production of Bioactive Compounds.

The species diversity of marine heterobranch sea slugs found on field trips around Bunaken Island (North Sulawesi, Indonesia) and adjacent islands of the Bunaken National Marine Park forms the basis of this review. In a survey performed in 2015, 80 species from 23 families were collected, including 17 new species. Only three of these have been investigated previously in studies from Indonesia. Combining species diversity with a former study from 2003 reveals in total 140 species from this locality. The diversity of bioactive compounds known and yet to be discovered from these organisms is summarized and related to the producer if known or suspected (might it be down the food chain, de novo synthesised from the slug or an associated bacterium). Additionally, the collection of microorganisms for the discovery of natural products of pharmacological interest from this hotspot of biodiversity that is presented here contains more than 50 species that have never been investigated before in regard to bioactive secondary metabolites. This highlights the great potential of the sea slugs and the associated microorganisms for the discovery of natural products of pharmacological interest from this hotspot of biodiversity.

Draft Genome Sequence of Burkholderia contaminans 293K04B, an Endosymbiont of the Sponge-Derived Fungus Stachylidium bicolor.

Here, we present the draft genome of the endofungal symbiotic bacterium Burkholderia contaminans 293K04B, isolated from Stachylidium bicolor 293K04 (Ascomycota). The fungus was originally isolated from the sponge Callyspongia cf. C. flammeaS. bicolor 293K04 produces the endolides A-B, bioactive cyclic peptides possibly biosynthesized by its endobacterium B. contaminans 293K04B.

Antimicrobial Potential of Bacteria Associated with Marine Sea Slugs from North Sulawesi, Indonesia.

Nudibranchia, marine soft-bodied organisms, developed, due to the absence of a protective shell, different strategies to protect themselves against putative predators and fouling organisms. One strategy is to use chemical weapons to distract predators, as well as pathogenic microorganisms. Hence, these gastropods take advantage of the incorporation of chemical molecules. Thereby the original source of these natural products varies; it might be the food source, de novo synthesis from the sea slug, or biosynthesis by associated bacteria. These bioactive molecules applied by the slugs can become important drug leads for future medicinal drugs. To test the potential of the associated bacteria, the latter were isolated from their hosts, brought into culture and extracts were prepared and tested for antimicrobial activities. From 49 isolated bacterial strains 35 showed antibiotic activity. The most promising extracts were chosen for further testing against relevant pathogens. In that way three strains showing activity against methicillin resistant Staphylococcus aureus and one strain with activity against enterohemorrhagic Escherichia coli, respectively, were identified. The obtained results indicate that the sea slug associated microbiome is a promising source for bacterial strains, which hold the potential for the biotechnological production of antibiotics.

Toolbox for Antibiotics Discovery from Microorganisms.

Microorganisms produce a vast array of biologically active metabolites. Such compounds are applied by humans to positively influence their health and, therefore, natural products serve as drug leads for pharmaceutical and medicinal chemistry. In this minireview, tools for the discovery and the production of potential drug leads are explained. A snapshot is provided, starting from the isolation of new producer strains, across genomic mining of (meta)genomes to identify biosynthetic gene clusters corresponding to natural products, toward heterologous expression to produce potential drug leads.

Oxidative dearomatisation: the key step of sorbicillinoid biosynthesis†Electronic supplementary information (ESI) available: Containing all experimental details. See DOI: 10.1039/c3sc52911hClick here for additional data file.

An FAD-dependent monooxygenase encoding gene (SorbC) was cloned from Penicillium chrysogenum E01-10/3 and expressed as a soluble protein in Escherichia coli. The enzyme efficiently performed the oxidative dearomatisation of sorbicillin and dihydrosorbicillin to give sorbicillinol and dihydrosorbicillinol respectively. Bioinformatic examination of the gene cluster surrounding SorbC indicated the presence of two polyketide synthase (PKS) encoding genes designated sorbA and sorbB. The gene sorbA-encodes a highly reducing iterative PKS while SorbB encodes a non-reducing iterative PKS which features a reductive release domain usually involved in the production of polyketide aldehydes. Using these observations and previously reported results from isotopic feeding experiments a new and simpler biosynthetic route to the sorbicillin class of secondary metabolites is proposed which is consistent with all reported experimental results.

Regio- and stereoselective oxidative phenol coupling in Aspergillus niger.

Piecing it together: Aspergillus niger produces kotanin by dimerization of the monomeric, polyketide-synthase-derived (PKS) 7-demethylsiderin. A combined approach, comprising bioinformatics and gene-deletion experiments, identified the biosynthetic cluster responsible for kotanin production. Homology modeling and substrate docking provide a rationale for the regio- and stereoselective phenol coupling reaction.

Rational domain swaps decipher programming in fungal highly reducing polyketide synthases and resurrect an extinct metabolite.

The mechanism of programming of iterative highly reducing polyketide synthases remains one of the key unsolved problems of secondary metabolism. We conducted rational domain swaps between the polyketide synthases encoding the biosynthesis of the closely related compounds tenellin and desmethylbassianin. Expression of the hybrid synthetases in Aspergillus oryzae led to the production of reprogrammed compounds in which the changes to the methylation pattern and chain length could be mapped to the domain swaps. These experiments reveal for the first time the origin of programming in these systems. Domain swaps combined with coexpression of two cytochrome P450 encoding genes from the tenellin biosynthetic gene cluster led to the resurrection of the extinct metabolite bassianin.

Catalytic role of the C-terminal domains of a fungal non-reducing polyketide synthase.

The in vivo activity of truncated forms of methylorcinaldehyde synthase shows that the synthase retains a hydrolytic release activity in the absence of reductive chain release and that chain-length is not controlled by the reductive release domain; experiments using a methyltransferase inhibitor suggest that methylation occurs prior to aromatisation.

Polyketide assembly lines of uncultivated sponge symbionts from structure-based gene targeting.

There is increasing evidence that uncultivated bacterial symbionts are the true producers of numerous bioactive compounds isolated from marine sponges. The localization and heterologous expression of biosynthetic genes could clarify this issue and provide sustainable supplies for a wide range of pharmaceuticals. However, identification of genes in the usually highly complex symbiont communities remains a challenging task. For polyketides, one of the most important groups of sponge-derived drug candidates, we have developed a general strategy that allows one to rapidly access biosynthetic gene clusters based on chemical moieties. Using this method, we targeted polyketide synthase genes from two different sponge metagenomes. We have obtained from a sponge-bacterial association a complete pathway for the rare and potent antitumor agent psymberin from Psammocinia aff. bulbosa. The data support the symbiont hypothesis and provide insights into natural product evolution in previously inaccessible bacteria.

Focal adhesion kinase regulates metastatic adhesion of carcinoma cells within liver sinusoids.

Organ-specific tumor cell adhesion to extracellular matrix (ECM) components and cell migration into host organs often involve integrin-mediated cellular processes that can be modified by environmental conditions acting on metastasizing tumor cells, such as shear forces within the blood circulation. Since the focal adhesion kinase (FAK) appears to be essential for the regulation of the integrin-mediated adhesive and migratory properties of tumor cells, its role in early steps of the metastatic cascade was investigated using in vitro and in vivo approaches. Human colon and hepatocellular carcinoma cells were used to study adhesive properties under static conditions and in a parallel plate laminar flow chamber in vitro. In addition, intravital fluorescence microscopy was used to investigate early interactions between circulating tumor cells and the microvasculature of potential target organs in vivo. Shear forces caused by hydrodynamic fluid flow induced Tyr-hyperphosphorylation of FAK in cell monolayers. Reduced expression of FAK or its endogenous inhibition by FAK-related non-kinase (FRNK) interfered with early adhesion events to extracellular matrix components under flow conditions. In contrast, tumor cell adhesion to endothelial cells under these conditions was not affected. Furthermore, down-regulation of FAK inhibited metastatic cell adhesion in vivo within the liver sinusoids. In summary, FAK appears to be involved in early events of integrin-mediated adhesion of circulating carcinoma cells under fluid flow in vitro and in vivo. This kinase may take part in the establishment of definitive adhesive interactions that enable adherent tumor cells to resist fluid shear forces, resulting in an organ-specific formation of distant metastases.

A new antioxidant isobenzofuranone derivative from the algicolous marine fungus Epicoccum sp.

The fungus Epicoccum sp., was isolated from the marine brown alga Fucus vesiculosus. After cultivation the fungus was investigated for its secondary metabolite content, and found to contain the new natural product 4,5,6-trihydroxy-7-methylphthalide (1, epicoccone), together with 5-(acetoxymethyl)-furan-2-carboxylic acid (2), furan-2-carboxylic acid (3), 5-(hydroxymethyl)-furan-2-carboxylic acid (4), (-)-(3 R,4 S)-4-hydroxymellein (5), and (-)-(3 R)-5-hydroxymellein (6). The structures of all compounds were determined by interpretation of their spectroscopic data (1D and 2D NMR, MS, UV, optical rotation and IR). Each isolate was tested for its antioxidative properties. Compound 1 was found to be potently active, showing 95 % DPPH radical scavenging effects at 25 microg/mL. Compound 1 also inhibited the peroxidation of linolenic acid in the TBARS assay (62 % inhibition at 37 microg/mL).

Antioxidative meroterpenoids from the brown alga Cystoseira crinita.

Six new tetraprenyltoluquinol derivatives (1-6), two new triprenyltoluquinol derivatives (7 and 8), and two new tetraprenyltoluquinone derivatives (9 and 10) were isolated from the brown alga Cystoseira crinita Duby together with four known tetraprenyltoluquinol derivatives (11-14). All structures were elucidated by employing spectroscopic techniques (NMR, MS, UV, and IR). Each compound was evaluated for its antioxidative properties in the TBARS and DPPH assay, and compounds 1, 2, 6, and 10-14 were additionally assessed in the TEAC and PCL assay. Hydroquinones were found to have powerful antioxidant activity.

New antioxidant hydroquinone derivatives from the algicolous marine fungus Acremonium sp.

A marine fungal isolate, identified as Acremonium sp., was mass cultivated and found to produce two novel hydroquinone derivatives, 7-isopropenylbicyclo[4.2.0]octa-1,3,5-triene-2,5-diol (1) and 7-isopropenylbicyclo[4.2.0]octa-1,3,5-triene-2,5-diol-5-beta-D-glucopyranoside (2). Compound 1 and its glucoside 2 possess a most unusual ring system. The new natural products (3R,4S)-3,4-dihydroxy-7-methyl-3,4-dihydro-1(2H)naphthalenone (3) and (3S,4S)-3,4-dihydroxy-7-methyl-3,4-dihydro-1(2H)-naphthalenone (4) were obtained as a 1:0.8 mixture. 2-(1-Methylethylidene)pentanedioic acid (5) was isolated for the first time as a natural product and its structure proven by X-ray analysis. In addition to these compounds an inseparable mixture of three new isomeric compounds, pentanedioic acid 2-(1-methylethylidene)-5-methyl ester (6), pentanedioic acid 2-(1-methylethylidene)-1-methyl ester (7), and pentanedioic acid 2-(1-methylethenyl)-5-methyl ester (8), was also obtained. Isolated together with the new compounds were three known hydroquinone derivatives, 9, 10, and 11. The structures of all compounds were determined by interpretation of their spectroscopic data (1D and 2D NMR, MS, UV, and IR). Each isolate was tested for its antioxidant properties, and compounds 1 and 9-11 were found to have significant activity.