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  • 1
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    Asperentin B, a New Inhibitor of the Protein Tyrosine Phosphatase 1B (2017)
    MDPI
    In:  Marine Drugs, 15 (6). p. 191.
    Details
    Publication Date: 2020-02-06
    Description: In the frame of studies on secondary metabolites produced by fungi from deep-sea environments we have investigated inhibitors of enzymes playing key roles in signaling cascades of biochemical pathways relevant for the treatment of diseases. Here we report on a new inhibitor of the human protein tyrosine phosphatase 1B (PTP1B), a target in the signaling pathway of insulin. A new asperentin analog is produced by an Aspergillus sydowii strain isolated from the sediment of the deep Mediterranean Sea. Asperentin B (1) contains an additional phenolic hydroxy function at C-6 and exhibits an IC50 value against PTP1B of 2 μM in vitro, which is six times stronger than the positive control, suramin. Interestingly, asperentin (2) did not show any inhibition of this enzymatic activity. Asperentin B (1) is discussed as possible therapeutic agents for type 2 diabetes and sleeping sickness.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3390/md15060191
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Lysoquinone-TH1, a New Polyphenolic Tridecaketide Produced by Expressing the Lysolipin Minimal PKS II in Streptomyces albus (2018)
    MDPI
    In:  Antibiotics, 7 (3). Art.Nr. 53.
    Details
    Publication Date: 2021-02-08
    Description: The structural repertoire of bioactive naphthacene quinones is expanded by engineering Streptomyces albus to express the lysolipin minimal polyketide synthase II (PKS II) genes from Streptomyces tendae Tü 4042 (llpD-F) with the corresponding cyclase genes llpCI-CIII. Fermentation of the recombinant strain revealed the two new polyaromatic tridecaketides lysoquinone-TH1 (7, identified) and TH2 (8, postulated structure) as engineered congeners of the dodecaketide lysolipin (1). The chemical structure of 7, a benzo[a]naphthacene-8,13-dione, was elucidated by NMR and HR-MS and confirmed by feeding experiments with [1,2-13C2]-labeled acetate. Lysoquinone-TH1 (7) is a pentangular polyphenol and one example of such rare extended polyaromatic systems of the benz[a]napthacene quinone type produced by the expression of a minimal PKS II in combination with cyclases in an artificial system. While the natural product lysolipin (1) has antimicrobial activity in nM-range, lysoquinone-TH1 (7) showed only minor potency as inhibitor of Gram-positive microorganisms. The bioactivity profiling of lysoquinone-TH1 (7) revealed inhibitory activity towards phosphodiesterase 4 (PDE4), an important target for the treatment in human health like asthma or chronic obstructive pulmonary disease (COPD). These results underline the availability of pentangular polyphenolic structural skeletons from biosynthetic engineering in the search of new chemical entities in drug discovery
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3390/antibiotics7030053
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  • 3
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    First Evidence of Dehydroabietic Acid Production by a Marine Phototrophic Gammaproteobacterium, the Purple Sulfur Bacterium Allochromatium vinosum MT86 (2018)
    MDPI
    In:  Marine Drugs, 16 (8). Art.Nr. 270.
    Details
    Publication Date: 2021-03-19
    Description: The production of secondary metabolites by a new isolate of the purple sulfur bacterium Allochromatium vinosum, which had shown antibiotic activities during a preliminary study, revealed the production of several metabolites. Growth conditions suitable for the production of one of the compounds shown in the metabolite profile were established and compound 1 was purified. The molecular formula of compound 1 (C20H28O2) was determined by high resolution mass spectra, and its chemical structure by means of spectroscopic methods. The evaluation of these data revealed that the structure of the compound was identical to dehydroabietic acid, a compound known to be characteristically produced by conifer trees, but so far not known from bacteria, except cyanobacteria. The purified substance showed weak antibiotic activities against Bacillus subtilis and Staphylococcus lentus with IC50 values of 70.5 µM (±2.9) and 57.0 µM (±3.3), respectively.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md16080270
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  • 4
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    Calcarides A–E, Antibacterial Macrocyclic and Linear Polyesters from a Calcarisporium Strain (2013)
    MDPI
    In:  Marine Drugs, 11 (9). pp. 3309-3323.
    Details
    Publication Date: 2018-03-02
    Description: Bioactive compounds were detected in crude extracts of the fungus, Calcarisporium sp. KF525, which was isolated from German Wadden Sea water samples. Purification of the metabolites from the extracts yielded the five known polyesters, 15G256α, α-2, β, β-2 and π (1–5), and five new derivatives thereof, named calcarides A–E (6–10). The chemical structures of the isolated compounds were elucidated on the basis of one- and two-dimensional NMR spectroscopy supported by UV and HRESIMS data. The compounds exhibited inhibitory activities against Staphylococcus epidermidis, Xanthomonas campestris and Propionibacterium acnes. As the antibacterial activities were highly specific with regard to compound and test strain, a tight structure-activity relationship is assumed.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.3390/md11093309
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  • 5
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    Spirocyclic Drimanes from the Marine Fungus Stachybotrys sp. Strain MF347 (2014)
    MDPI
    In:  Marine Drugs, 12 (4). pp. 1924-1938.
    Details
    Publication Date: 2018-03-02
    Description: A novel spirocyclic drimane coupled by two drimane fragment building blocks 2 and a new drimane 1 were identified in mycelia and culture broth of Stachybotrys sp. MF347. Their structures were established by spectroscopic means. This is the first example of spirocyclic drimane coupled by a spirodihydrobenzofuranlactam unit and a spirodihydroisobenzofuran unit; and the connecting position being N-C instead of an N and N connecting unit. Strain MF347 produced also the known spirocyclic drimanes stachybocin A (12) and stachybocin B (11) featured by two sesquiterpene-spirobenzofuran structural units connected by a lysine residue; the known spirocyclic drimanes chartarlactam O (5); chartarlactam K (6); F1839A (7); stachybotrylactam (8); stachybotramide (9); and 2α-acetoxystachybotrylactam acetate (10); as well as ilicicolin B (13), a known sesquiterpene. The relative configuration of two known spirobenzofuranlactams (3 and 4) was determined. All compounds were subjected to biological activity tests. The spirocyclic drimane 2, 11, and 12, as well as the sesquiterpene 13, exhibited antibacterial activity against the clinically relevant methicillin-resistant Staphylococcus aureus (MRSA).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md12041924
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  • 6
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    Isolation of extremely halophilic phototrophic bacteria from the alkaline Wadi Natrun, Egypt (1978)
    Schweizerbart
    In:  Archiv für Hydrobiologie, 84 . pp. 381-388.
    Details
    Publication Date: 2015-03-24
    Type: Article , PeerReviewed
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  • 7
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    Bacterial and archaeal diversity in high altitude wetlands of the Chilean Altiplano (2013)
    Schweizerbart
    In:  Fundamental and Applied Limnology : Archiv für Hydrobiologie, 182 (2). pp. 135-159.
    Details
    Publication Date: 2019-04-04
    Description: The microbial diversity of five unconnected high altitude (≥ 3800 m a.s.l.) wetlands from the Chilean Altiplano was analyzed by a culture-independent approach, using 16 S rRNA gene sequences of different microbial groups. The wetlands (Chungara Lake, Parinacota wetland, Piacota Lake, Salar de Huasco and Salar de Ascotan) differed in terms of habitat type and physicochemical properties. The bacterial communities of these systems were dominated by Bacteroidetes (24-94 % of the clones) and Proteobacteria (Alpha, Beta, Gamma and Delta subgroups) with smaller contributions by the Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Chloroflexi, Cyanobacteria, Acidobacteria, Deinococcus-Thermus and Candidate Division WS3. Fourteen phylotypes matching Alphaproteobacteria were part of the marine Roseobacter clade, representing new clusters of this group. Archaeal diversity was much lower than that seen for bacteria, and was dominated by Euryarchaeota; however Crenarchaeota were also present. Considering the large differences in microbial community composition between sites and samples, the presence of eleven phylotypes common to two or more habitats is highlighted. The frequent presence of new taxa in different phylogenetic groups in the altiplanic wetlands studied here revealed the unique characteristics of Bacteria and Archaea in these fragile Andean ecosystems.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1127/1863-9135/2013/0393
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  • 8
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    Effect of salinity on cyanobacterial community composition along a transect from Fuliya spring into the water of Lake Kinneret, Israel (2013)
    Schweizerbart
    In:  Fundamental and Applied Limnology : Archiv für Hydrobiologie, 182 (2). pp. 99-107.
    Details
    Publication Date: 2019-04-04
    Description: Cyanobacterial community composition was studied along a salinity gradient from the saline Spring Fuliya towards the water column of Lake Kinneret. The samples included a gradient of salinities ranging from 4270 mg Cl L-1 (Saline Spring) to 239 mg Cl L-1 (Lake Kinneret). Denaturing gradient gel electrophoresis (DGGE) and cloning of the 16 S rRNA gene, as well as cloning and sequencing of the psbA gene, were used to characterize cyanobacterial community composition. Despite the differences in salinity, similar cyanobacterial communities were observed in the lake and the saline spring, the only exception being the highest salinity sample (4270 mg Cl L-1). Both, DGGE patterns and results of the clone libraries revealed the dominance of cyanobacteria with colonial Gloeocapsa and unicellular Synechococcus as the closest known cultured relatives, independently of the salinity. These results suggest that cyanobacterial populations inhabiting this freshwater lake and its saline sources can adapt to a wide range of salinities.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1127/1863-9135/2013/0407
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  • 9
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    Champacyclin, a New Cyclic Octapeptide from Streptomyces Strain C42 Isolated from the Baltic Sea (2013)
    MDPI
    In:  Marine Drugs, 11 (12). pp. 4834-4857.
    Details
    Publication Date: 2018-03-02
    Description: New isolates of Streptomyces champavatii were isolated from marine sediments of the Gotland Deep (Baltic Sea), from the Urania Basin (Eastern Mediterranean), and from the Kiel Bight (Baltic Sea). The isolates produced several oligopeptidic secondary metabolites, including the new octapeptide champacyclin (1a) present in all three strains. Herein, we report on the isolation, structure elucidation and determination of the absolute stereochemistry of this isoleucine/leucine (Ile/Leu = Xle) rich cyclic octapeptide champacyclin (1a). As 2D nuclear magnetic resonance (NMR) spectroscopy could not fully resolve the structure of (1a), additional information on sequence and configuration of stereocenters were obtained by a combination of multi stage mass spectrometry (MSn) studies, amino acid analysis, partial hydrolysis and subsequent enantiomer analytics with gas chromatography positive chmical ionization/electron impact mass spectrometry (GC-PCI/EI-MS) supported by comparison to reference dipeptides. Proof of the head-to-tail cyclization of (1a) was accomplished by solid phase peptide synthesis (SPPS) compared to an alternatively side chain cyclized derivative (2). Champacyclin (1a) is likely synthesized by a non-ribosomal peptide synthetase (NRPS), because of its high content of (d)-amino acids. The compound (1a) showed antimicrobial activity against the phytopathogen Erwinia amylovora causing the fire blight disease of certain plants.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md11124834
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  • 10
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    Two New Antibiotic Pyridones Produced by a Marine Fungus, Trichoderma sp. Strain MF106 (2014)
    MDPI
    In:  Marine Drugs, 12 (3). pp. 1208-1219.
    Details
    Publication Date: 2018-03-02
    Description: Two unusual pyridones, trichodin A (1) and trichodin B (2), together with the known compound, pyridoxatin (3), were extracted from mycelia and culture broth of the marine fungus, Trichoderma sp. strain MF106 isolated from the Greenland Seas. The structures of the new compounds were characterized as an intramolecular cyclization of a pyridine basic backbone with a phenyl group. The structure and relative configuration of the new compounds were established by spectroscopic means. The new compound 1 and the known compound 3 showed antibiotic activities against the clinically relevant microorganism, Staphylococcus epidermidis, with IC50 values of 24 μM and 4 μM, respectively.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/md12031208
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