Search

Graphical abstract Highlights • A cyclic peptide, croissamide, was discovered from a marine cyanobacterium. • Gross structure was determined by spectroscopic analyses. • Absolute stereochemistry was determined by chiral HPLC analyses of acid hydrolysates. • Structurally, croissamide contains five prolines and one N -prenylated tryptophan. Abstract Croissamide, a proline-rich cyclic peptide that contains an N -prenylated tryptophan, was isolated from a marine cyanobacterium Symploca sp. Its gross structure was determined by spectroscopic analyses, and the absolute configuration was established based on chiral HPLC analyses of acid hydrolysates. [ABSTRACT FROM AUTHOR]

A new siderophore containing a 4,5-dihydroimidazole moiety was isolated from Pseudoalteromonas piscicida S2040 together with myxochelins A and B, alteramide A and its cycloaddition product, and bromo- and dibromoalterochromides. The structure of pseudochelin A was established by spectroscopic techniques including 2D NMR and MS/MS fragmentation data. In bioassays selected fractions of the crude extract of S2040 inhibited the opportunistic pathogen Pseudomonas aeruginosa . Pseudochelin A displayed siderophore activity in the chrome azurol S assay at concentrations higher than 50 μM, and showed weak activity against the fungus Aspergillus fumigatus , but did not display antibacterial, anti-inflammatory or anticonvulsant activity. [ABSTRACT FROM AUTHOR]

Natural products containing carbon–phosphorus bonds elicit important bioactivity in many organisms. l -Phosphinothricin contains the only known naturally-occurring carbon–phosphorus–carbon bond linkage. In actinomycetes, the cobalamin-dependent radical S -adenosyl- l -methionine (SAM) methyltransferase PhpK catalyzes the formation of the second C–P bond to generate the complete C–P–C linkage in phosphinothricin. Here we use electron paramagnetic resonance and nuclear magnetic resonance spectroscopies to characterize and demonstrate the activity of a cobalamin-dependent radical SAM methyltransferase denoted SD_1168 from Shewanella denitrificans OS217, a marine bacterium that has not been reported to synthesize phosphinothricin. Recombinant, refolded, and reconstituted SD_1168 binds a four-iron, four-sulfur cluster that interacts with SAM and cobalamin. In the presence of SAM, a reductant, and methylcobalamin, SD_1168 surprisingly catalyzes the P-methylation of N-acetyl-demethylphosphinothricin and demethylphosphinothricin to produce N-acetyl-phosphinothricin and phosphinothricin, respectively. In addition, this enzyme is active in the absence of methylcobalamin if the strong reductant titanium (III) citrate and hydroxocobalamin are provided. When incubated with [methyl- 13 C] cobalamin and titanium citrate, both [methyl- 13 C] and unlabeled N-acetylphosphinothricin are produced. Our results suggest that SD_1168 catalyzes P-methylation using radical SAM-dependent chemistry with cobalamin as a coenzyme. In light of recent genomic information, the discovery of this P-methyltransferase suggests that S. denitrificans produces a phosphinate natural product. [ABSTRACT FROM AUTHOR]

Fractionation of the ethyl acetate extract of the marine bacterium Bacillus pumilus isolated from the black coral Antipathes sp. led to the isolation of five compounds: cyclo-(L-Leu-L-Pro) (1), 3-hydroxyacetylindole (2), N-acetyl-β-oxotryptamine (3), cyclo-(L-Phe-L-Pro) (4), and 3-formylindole (5). The structures of compounds 1-5 were established by spectroscopic analyses, including HRESITOF-MS and NMR (1H, 13C, HSQC, HMBC and COSY). Compounds 2, 3 and 5 caused the inhibition on the growth of Trypanosoma cruzi (T. cruzi), with IC50 values of 20.6, 19.4 and 26.9 μM, respectively, with moderate cytotoxicity against Vero cells. Compounds 1-5 were found to be inactive when tested against Plasmodium falciparum and Leishmania donovani, therefore showing selectivity against T. cruzi parasites. [ABSTRACT FROM AUTHOR]

Abstract: Some marine bacteria collected around deep-sea hydrothermal vents are able to produce, in laboratory conditions, complex and innovative exopolysaccharides. In a previous study, the mesophilic strain Alteromonas macleodii subsp. fijiensis biovar deepsane was collected on the East Pacific Rise at 2600m depth. It was isolated from a polychaete annelid Alvinella pompejana and is able to synthesise and excrete the exopolysaccharide deepsane. Biological activities have been screened and some protective properties have been established. Deepsane is commercially available in cosmetics under the name of Abyssine® for soothing and reducing irritation of sensitive skin against chemical, mechanical and UVB aggression. This study presents structural data for this original and complex bacterial exopolysaccharide and highlights some structural similarities with other known EPS produced by marine Alteromonas strains. [Copyright &y& Elsevier]

Luminous marine bacteria usually emit bluish-green light with a peak emission wavelength (λmax) at about 490 nm. Some species belonging to the genus Photobacterium are exceptions, producing an accessory blue fluorescent protein (lumazine protein: LumP) that causes a blue shift, from λmax ≈ 490 to λmax ≈ 476 nm. However, the incidence of blue-shifted light emission or the presence of accessory fluorescent proteins in bacteria of the genus Vibrio has never been reported. From our spectral analysis of light emitted by 16 luminous strains of the genus Vibrio, it was revealed that most strains of Vibrio azureus emit a blue-shifted light with a peak at approximately 472 nm, whereas other Vibrio strains emit light with a peak at around 482 nm. Therefore, we investigated the mechanism underlying this blue shift in V. azureus NBRC 104587T. Here, we describe the blue-shifted light emission spectra and the isolation of a blue fluorescent protein. Intracellular protein analyses showed that this strain had a blue fluorescent protein (that we termed VA- BFP), the fluorescent spectrum of which was almost identical to that of the in vivo light emission spectrum of the strain. This result strongly suggested that VA- BFP was responsible for the blue-shifted light emission of V. azureus. [ABSTRACT FROM AUTHOR]

Abstract: Reported herein is the isolation and structure elucidation of three highly modified peptides, actinoramides A–C (1–3), which are produced by a marine bacterium closely related to the genus Streptomyces. The planar structures of the actinoramides, which are composed of the unusual amino acids 2-amino-4-ureidobutanoic acid and 4-amino-3-hydroxy-2-methyl-5-phenylpentanoic acid, were assigned by chemical transformations and by interpretation of spectroscopic data, while the absolute configuration of these new peptides were defined by application of the advanced Marfey’s and Mosher’s methods. [Copyright &y& Elsevier]

Chemical analysis of a marine-derived Streptomycessp. (CMB-M0423) isolated from beach sand off Heron Island, Australia, yielded three new members of the rare pyrroloterpene biosynthetic structure class. Identified by detailed spectroscopic analysis as the first reported examples of naturally occurring 2-nitropyrroles, heronapyrroles A−C (1−3) displayed promising biological activitywith low to submicromolar IC50activity against Gram-positive bacteria but no cytotoxicity toward mammalian cell lines. [ABSTRACT FROM AUTHOR]

An acidic O-specific polysaccharide containing L-rhamnose, 2-acetamido-2-deoxy-D-galactose, 2,6-dideoxy-2-(N-acetyl-L-threonine)amino-D-galactose, and 2-acetamido-2-deoxy-D-mannuronic acid was obtained by mild acid degradation of the lipopolysaccharide of the marine bacterium Pseudoalteromonas agarivorans KMM 232 (R-form) followed by gel-permeation chromatography. The polysaccharide was subjected to Smith degradation to give a modified polysaccharide with trisaccharide repeating unit containing L-threonine. The initial and modified polysaccharides were studied by sugar analysis and 1H- and 13C-NMR spectroscopy, including COSY, TOCSY, ROESY, and HSQC experiments, and the structure of the branched tetrasaccharide repeating unit of the polysaccharide was established. [ABSTRACT FROM AUTHOR]

Abstract: Recent developments in whole-cell spectroscopic methods allow rapid characterization of microorganisms of interest to human health, but have yet to be widely applied to marine microbiological studies. In this study of bacteria associated with the kelp Laminaria digitata, we have isolated 18 epiphytic bacterial strains from several thalli, sequenced their 16S rDNA, built corresponding phylogenetic trees, and characterized them using spectroscopic methods. Molecular taxonomy revealed Gram+ Actinobacteria and Gram− Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. Twelve marine reference strains (Gram+ Firmicutes, and Gram− Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes) were treated accordingly. Whole-cell MALDI-TOF MS spectral profiles of 29 of the 30 strains were built into a database against which 16 replicate spectra of each strain were compared and categorized into groups. The proton HR-MAS NMR stack plots allowed visual delineation into taxonomic groups according to their most common peaks, in agreement with identifiable compounds from corresponding D2O solution spectra. With both methods, these groups corresponded to taxa identified by 16S rDNA sequences, MALDI-TOF MS being more discriminative than HR-MAS NMR. Culture age did not influence the spectral signatures in both approaches. Most cells grown under minimal conditions (VNSS medium) afforded HR-MAS NMR profiles markedly different to those grown in enriched conditions (ZoBell medium), indicating different adaptive metabolic responses between the two media. Spectral signatures obtained under strictly controlled conditions can be used as rapid and reliable tools for taxonomic purposes and as markers of physiological status. [Copyright &y& Elsevier]

Bioassay-guided fractionation of the cytotoxic constituents of the marine cyanobacterium Lyngbyasp. led to the isolation of biselyngbyaside (1), a new 18-membered macrolide glycoside. The structure of 1was established by spectroscopic analysis including 2D-NMR techniques and by synthetic studies. Biselyngbyaside (1) exhibits broad-spectrum cytotoxicity in a human tumor cell line panel. [ABSTRACT FROM AUTHOR]

A novel thiazole alkaloid, neobacillamide A 1, together with a known related one, bacillamide C 4, was isolated from the bacterium Bacillus vallismortisC89, associated with the South China Sea sponge Dysidea avara.The structure of the new compound was elucidated on the basis of its spectroscopic data. A plausible biosynthetic pathway is proposed. Neobacillamide A represents the first example of a thiazolecarboxamide bearing a 2phenylethylamine moiety. [ABSTRACT FROM AUTHOR]

Aims: To purify the biosurfactant produced by a marine Bacillus circulans strain and evaluate the improvement in surface and antimicrobial activities. Methods and Results: The study of biosurfactant production by B. circulans was carried out in glucose mineral salts (GMS) medium using high performance thin layer chromatography (HPTLC) for quantitative estimation. The biosurfactant production by this strain was found to be growth-associated showing maximum biosurfactant accumulation at 26 h of fermentation. The crude biosurfactants were purified using gel filtration chromatography with Sephadex® G-50 matrix. The purification attained by employing this technique was evident from UV–visible spectroscopy and TLC analysis of crude and purified biosurfactants. The purified biosurfactants showed an increase in surface activity and a decrease in critical micelle concentration values. The antimicrobial action of the biosurfactants was also enhanced after purification. Conclusions: The marine B. circulans used in this study produced biosurfactants in a growth-associated manner. High degree of purification could be obtained by using gel filtration chromatography. The purified biosurfactants showed enhanced surface and antimicrobial activities. Significance and Impact of the Study: The antimicrobial biosurfactant produced by B. circulans could be effectively purified using gel filtration and can serve as new potential drugs in antimicrobial chemotherapy. [ABSTRACT FROM AUTHOR]

Abstract: A possibility has been suggested of applying the EPS produced by Rhodococcus rhodochrous strain S-2 (S-2 EPS) to the bioremediation of oil-contaminated environments, because its addition, together with minerals, to oil-contaminated seawater resulted in emulsification of the oil, increased the degradation of polyaromatic hydrocarbons (PAH) of the oil, and led to the dominance of PAH-degrading marine bacteria. To understand the underlying principles of these phenomena, we determined the chemical structure of the sugar chain of S-2 EPS. The EPS was found to be composed of d-galactose, d-mannose, d-glucose, and d-glucuronic acid, in a molar ratio of 1:1:1:1. In addition, 0.8% (w/w) of octadecanoic acid and 2.7% (w/w) of hexadecanoic acid were also contained in its structure. By 1H and 13C NMR spectroscopy, including 2D DQF-COSY, TOCSY, HMQC, HMBC, and NOESY experiments, as well as chemical and enzymatic analyses, the polysaccharide was shown to consist of tetrasaccharide repeating units with the following structure: Display Omitted [Copyright &y& Elsevier]

Abstract: The O-chain polysaccharide of the lipopolysaccharide from the halophilic marine bacterium Pseudoalteromonas carrageenovora IAM 12662T was characterized. The structure was studied by means of chemical analysis and 2D NMR spectroscopy of the de-O-acylated lipopolysaccharide and shown to be the following:▪Col is colitose, 3,6-di-deoxy-l-xylo-hexose. [Copyright &y& Elsevier]

Novel lipooligosaccharide components were isolated and identified from the lipooligosaccharide fraction of the halophilic marine bacterium Pseudoalteromonas issachenkonii type strain KMM 3549T. The complete structure was achieved by chemical analysis, 2D NMR spectroscopy and MALDI mass spectrometry as the following:All sugars are d-pyranoses. Hep is l-glycero-d-manno-heptose, Kdo is 3-deoxy-d-manno-oct-2-ulosonic acid, P is phosphate, residues and substituents in italic are not stoichiometrically linked. In addition, by MALDI mass spectrometry of the intact LOS, the lipid A moiety was also identified as a mixture of penta-, tetra- and triacylated species. [Copyright &y& Elsevier]

The phenotypic features of strain GJ1B. an unidentified marine bacterium that degrades agar [Young. K. S., Bhattacharjee. S. S. & Yaphe, W. (1978) Carbohydr. Res. 66, 207-212], were investigated and its agarolytic system was characterized using 13C-NMR spectroscopy to analyse the agarose degradation products, The bacterium was assigned to the genus Alteromonas and the new combination A, agarlyticus (Cataldi) is proposed. An α-agarase, i.e specific for the α(1→3) linkages present in agarose, was purified to homogeneity from the culture supernatant by affinity chromatography on cross-linked agarose (Sepharose CL-6B) and by anion-exchange chromatograpy (Mono Q column). The major end product of agarose hydrolysis using the purified enzyme was agarotetraose. Using SDS/PAGE, the purified α-agarase was detected as a single band with a molecular mass of 180 kDa. After the affinity-chromatography step, however, the native molecular mass was approximately 360 kDa, suggesting that the native enzyme is a dimer which is dissociated to active subunits by anion-exchange chromatography. The isolectric point was estimated to be 5.3. Enzyme activity was observed using agar as the substrate over the pH range 6,0-9.0 with a maximum value at pH 7.2 in Mops or Tris buffer, The enzyme was inactivated by prolonged treatment at a pH below 6.5, or by temperatures over 45°C or by removing calcium. In addition, a β-galactosidase specific for the end products of the α-agarase was present in the α-agarase affinity-chromatography fraction, probably as part of a complex with this enzyme, The degradation of agarose by this agarase complex yielded a mixture of oligosaccharides in the agarotetraose series and the agarotriose series, the latter consisting of otigosaccharides with an odd number of galactose residues. [ABSTRACT FROM AUTHOR]