Marine Bacteria, XLVII - Psychrotolerant Bacteria from Extreme Antarctic Habitats as Producers of Rare Bis- and Trisindole Alkaloids.

From the gastrointestinal tract of a fish dredged near the South Orkney Islands in Antarctica, we isolated the psychrotolerant bacterial strain T262, which belongs to the species Vibrio splendidus. Investigation of this strain led to the isolation of a series of 15 bis- and trisindole derivatives. Among them, six new indole alkaloids, namely, turbomycin C [4'-n-butoxyphenyl-bis(1H-indol-3-yl)methane, 1a], turbomycin D [4'-n-propoxyphenyl-bis(1H-indol-3-yl)methane, 1b], turbomycin E [4'-ethoxyphenyl-bis(1H-indol-3-yl)methane, 1c], turbomycin F [4'-methoxy-3',5'-dinitrophenyl-bis(1H-indol-3-yl)methane, 2], trisindolal (3a), and 4-(1H-indol-3-yl-sulfanyl)phenol (4). Another new bisindole derivative elucidated as 2-(indol-3-ylmethyl)-indol-3-ylethanol (7a) was obtained together with six known compounds from the psychrotolerant Arthrobacter psychrochitiniphilus strain T406, isolated from the excrement of penguins. Some of the isolated compounds showed activity against both gram-positive and gram-negative bacteria at 10 µg/paper disk. Trisindolal (3a) was active against the peronosporomycetes Botrytis cinerea and Phytophthora infestans, and some of the indole derivatives indicated promising cytotoxicity towards human tumor cell lines. By exhibiting a mean IC50 of 0.45 µg/mL (1.17 µM), trisindolal (3a) showed pronounced potency and selectivity in a panel of 11 human tumor cell lines derived from 10 different tumor histotypes.

Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean.

Roughly 60% of the Earth's outer surface is composed of oceanic crust formed by volcanic processes at mid-ocean ridges. Although only a small fraction of this vast volcanic terrain has been visually surveyed or sampled, the available evidence suggests that explosive eruptions are rare on mid-ocean ridges, particularly at depths below the critical point for seawater (3,000 m). A pyroclastic deposit has never been observed on the sea floor below 3,000 m, presumably because the volatile content of mid-ocean-ridge basalts is generally too low to produce the gas fractions required for fragmenting a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel ridge in the Arctic Basin at 85 degrees E, to acquire photographic and video images of 'zero-age' volcanic terrain on this remote, ice-covered ridge. Here we present images revealing that the axial valley at 4,000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele), covering a large (>10 km(2)) area. At least 13.5 wt% CO(2) is necessary to fragment magma at these depths, which is about tenfold the highest values previously measured in a mid-ocean-ridge basalt. These observations raise important questions about the accumulation and discharge of magmatic volatiles at ultraslow spreading rates on the Gakkel ridge and demonstrate that large-scale pyroclastic activity is possible along even the deepest portions of the global mid-ocean ridge volcanic system.

Mansouramycins A-D, cytotoxic isoquinolinequinones from a marine streptomycete.

Chemical screening of the ethyl acetate extract from the marine-derived Streptomyces sp. isolate Mei37 resulted in five isoquinolinequinones, four new derivatives, mansouramycin A-D (1, 3-5), and the known 3-methyl-7-(methylamino)-5,8-isoquinolinedione (2). Their structures were elucidated by NMR and MS techniques and by comparison with related compounds. Cytotoxicity profiling of the mansouramycins in a panel of up to 36 tumor cell lines indicated significant cytotoxicity of several derivatives, with pronounced selectivity for non-small cell lung cancer, breast cancer, melanoma, and prostate cancer cells.

Electrospray ionization mass spectra of piperazimycins A and B and gamma-butyrolactones from a marine-derived Streptomyces sp.

Chemical investigation of the marine-derived Streptomyces sp. Act8015 led to the isolation of two cyclic peptide antibiotics, piperazimycins A and B (1a, 1b). Their structures were confirmed on the basis of a detailed HRESI-MS/MS analysis. Additionally, a new butanolide, 4,10-dihydroxy-10-methyl-dodecan-4-olide (2), and the respective acid, 4,10-dihydroxy-10-methyl-dodecanoic acid (3a) were identified. Further isolated compounds were staurosporin, adenine, indole-3-carboxylic acid, ferulic acid, tryptophol, and three gamma-butyrolactones: virginiae butanolide E (4e) and Graefe's Factors I (4f) and III (4g). The structures of 2 and 3a were confirmed by detailed 1D and 2D NMR studies and MS spectra and by comparison with related structures. A full signal assignment of virginiae butanolide E (4e) is reported here for the first time.

New aromatic nitro compounds from Salegentibacter sp. T436, an Arctic Sea ice bacterium: taxonomy, fermentation, isolation and biological activities.

Nineteen aromatic nitro compounds were isolated from the culture broth of an Arctic sea ice bacterium. Four of these compounds are new and six compounds are reported from a natural source for the first time. The new natural products showed weak antimicrobial and cytotoxic activities. 2-nitro-4-(2'-nitroethenyl)-phenol was the most potent antimicrobial and cytotoxic substance. Some of the compounds exhibit plant growth modulating activities. Based on its biochemical properties and the 16S rRNA gene sequence, the producing strain can be described as a distinct species within the genus Salegentibacter.

Isolation and Structural Elucidation of Nitrogenous Secondary vetabolites from Terrestrial and Marine Streptomyces spp.

Screening and chromatography of extracts from a terrestrial and a marine-derived streptomycete yielded two new nitrogenous benzene derivatives, namely (S)-N-[3-hydroxy--(4-hydroxyphenyl)-propyl]-acetamide (1a), and (R)-2-(l-methyl-2-oxopropylamino)-benzoic acid (2). Additionally, eight known compounds were. isolated, 2-acetamidophenol, phenazine-l-carboxylic acid, phenazine-l-carboxylic acid methyl ester, perlolyrin, tyrosol, uracil, and anthranilic acid. The structures of the new compounds were deduced from high resolution mass, ID and 2D NMR spectra and by comparison with related compounds from the literature. The absolute configuration of ia and 2 was determined by comparison of experimental and calculated CD and ORD data.

Bacterial communities and chemical parameters in soils and coastal sediments in response to diesel spills at Carlini Station, Antarctica.

A diesel spill occurring at Carlini Station (King George Island (Isla 25 de Mayo), South Shetland Islands) in 2009 started the study of the fate of the hydrocarbons and their effect on the bacterial communities of the Potter Cove ecosystem. Soils and sediments were sampled across the 200-meter long diesel plume towards Potter Cove four and 15months after the spill. The sampling revealed a second fuel leakage from an underground pipeline at the spill site. The hydrocarbon fraction spilt over frozen and snow-covered ground reached the sea and dispersed with the currents. Contrary, diesel that infiltrated unfrozen soil remained detectable for years, and was seeping with ground water towards coastal marine sediments. Structural changes of the bacterial communities as well as hydrocarbon, carbon and nitrogen contents were investigated in sediments in front of the station, two affected terrestrial sites, and a terrestrial non-contaminated reference site. Bacterial communities (16S rRNA gene clone libraries) changed over time in contaminated soils and sediments. At the underground seepage site of highest contamination (5812 to 366µgg-1dw hydrocarbons from surface to 90-cm depth), communities were dominated by Actinobacteria (18%) and a betaproteobacterium closely related to Polaromonas naphthalenivorans (40%). At one of the spill sites, affected exclusively at the surface, contamination disappeared within one year. The same bacterial groups were enriched at both contaminated sites. This response at community level suggests that the cold-adapted indigenous microbiota in soils of the West Antarctic Peninsula have a high potential for bioremediation and can support soil cleaning actions in the ecosystem. Intensive monitoring of pollution and site assessment after episodic fuel spills is required for decision-making towards remediation strategies.

Oligomycins and pamamycin homologs impair motility and induce lysis of zoospores of the grapevine downy mildew pathogen, Plasmopara viticola.

Four antibiotics (pamamycin, oligomycin A, oligomycin B and echinosporin) were isolated and characterized from the fermentation broth of the marine Streptomyces strains B8496 and B8739. Bioassays revealed that each of these compounds impaired motility and caused subsequent lysis of P. viticola zoospores in a dose- and time-dependent manner. Pamamycin displayed the strongest motility inhibitory and lytic activities (IC50 0.1 µg mL(-1)) followed by oligomycin B (IC50 0.15 and 0.2 µg mL(-1)) and oligomycin F (IC50 0.3 and 0.5 µg mL(-1)). Oligomycin A and echinosporin also showed motility inhibitory activities against the zoospores with IC50 values of 3.0 and 10.0 µg mL(-1), respectively. This is the first report of motility inhibitory and lytic activities of these antibiotics against zoospores of a phytopathogenic peronosporomycete. Structures of all the isolated compounds were determined based on detailed spectroscopic analysis.

Influence of crude oil on changes of bacterial communities in Arctic sea-ice.

The danger of a petroleum hydrocarbon spillage in the polar, ice-covered regions is increasing due to oil exploration in Arctic offshore areas and a growing interest in using the Northern Sea Route (NSR) as an alternative transportation route for Arctic oil and gas. However, little is known about the potential impact of accidental oil spills on this environment. We investigated the impact of crude oil on microbial community composition in six different Arctic sea-ice samples incubated with crude oil at 1 degrees C in microcosms for one year. Alterations in the composition of bacterial communities were analyzed with the culture-independent molecular methods DGGE (denaturing gradient gel electrophoresis) and FISH (fluorescence in situ hybridization). DGGE, FISH and cultivation methods revealed a strong shift in community composition toward the gamma-proteobacteria in sea-ice and melt pool samples incubated with crude oil. Marinobacter spp., Shewanella spp. and Pseudomonas spp. were the predominant phylotypes in the oil-treated microcosms. The ability of indigenous sea-ice bacteria to degrade hydrocarbons at low temperature (1 degrees C) was tested using four representative strains cultivated from sea-ice enriched with crude oil. [14C]Hexadecane was degraded by the sea-ice isolates at 20-50% capacity of the mesophilic type strain Marinobacter hydrocarbonoclasticus, a known hydrocarbon degrader, incubated at 22 degrees C.

1-Hydroxy-1-norresistomycin and resistoflavin methyl ether: new antibiotics from marine-derived streptomycetes.

Cultivation of the marine-derived streptomycete isolate B8005 delivered three known antibiotics, resistomycin (1), resistoflavin (3a) and tetracenomycin (4), and a further member of the rare resistomycin class, the weakly antibiotically active 1-hydroxy-1-norresistomycin (2). From a related marine strain B4842, 1 and resistoflavin methyl ether (3b) have been isolated. The formation of 2 is of interest from a biosynthetic point of view.

Volatile organic compounds from arctic bacteria of the Cytophaga-Flavobacterium-Bacteroides group: a retrobiosynthetic approach in chemotaxonomic investigations.

Volatile organic compounds emitted by different marine arctic strains of the Cytophaga-Flavobacterium-Bacteroides group were investigated by using a modified closed-loop stripping apparatus (CLSA). Seven of nine strains emitted volatiles, dominated by methyl ketones, in specific patterns. The methyl ketones were aliphatic saturated, or unsaturated, and comprised 12 to 18 C-atoms, sometimes with terminal Me branches. They were identified by GC/MS, retention-index calculations, derivatization with dimethyl disulfide for C=C bond location, and GC/FTIR to elucidate their uniform (Z)-configuration. The proposed structures of all methyl ketones were subsequently confirmed by synthesis, while the absolute configuration of chiral volatiles was elucidated by stereoselective synthesis. From retrobiosynthetic considerations, it was found that strain ARK10267 uses mainly valine, and strain ARK10063 mainly isoleucine for formation of starters for the ketone biosynthesis, which is correlated to fatty acid biosynthesis. Four strains (ARK10223, ARK10044, ARK10141, and ARK10146) use leucine. These separations are supported by phylogenetic affiliations based on 16S rRNA. Strain ARK10255b, in the course of this study found to be not a member of the Cytophaga-Flavobacterium-Bacteroides phylum, did not emit aliphatic ketones of medium chain length, but methionine-derived 4-(methylsulfanyl)butan-2-one and corresponding 4-(methylsulfanyl)butan-2-ol. Most of the compounds described have not been reported previously from nature.

Himalomycin A and B: isolation and structure elucidation of new fridamycin type antibiotics from a marine Streptomyces isolate.

In our screening of marine Streptomycetes for bioactive compounds, in addition to the known metabolites rabelomycin (1), fridamycin D (2b), N-benzylacetamide and N-(2'-phenylethyl)acetamide, two new anthracycline antibiotics designated as himalomycin A (2c) and B (2d) were isolated from the culture broth of the marine Streptomyces sp. isolate B6921. The structure of the new antibiotics was determined by comparison of the NMR data with those of fridamycin D (2b) and by detailed interpretation of mass, 1D and 2D NMR spectra.

Parimycin: isolation and structure elucidation of a novel cytotoxic 2,3-dihydroquinizarin analogue of gamma-indomycinone from a marine streptomycete isolate.

In our screening of actinomycetes from the marine environment for bioactive components, a new antibiotic with a novel structure designated as parimycin was obtained from the culture broth of Streptomyces sp. isolate B8652. The structure of the new antibiotic was determined by spectroscopic methods and by comparison of the NMR data with those of the structurally related gamma-indomycinone.

Chalcomycin B, a new macrolide antibiotic from the marine isolate Streptomyces sp. B7064.

In our screening of marine streptomycete isolates for bioactive components, a new macrolide antibiotic designated as chalcomycin B (1b) was isolated from the culture broth of a marine Streptomycete isolate B7064 together with chalcomycin (1a) as the active principles. The structure of the new antibiotic was determined by EI and ESI MS, 1H, 13C and 2D NMR spectroscopy and by comparison of the NMR data with those of chalcomycin.

Anti-cancer and antibacterial trioxacarcins with high anti-malaria activity from a marine Streptomycete and their absolute stereochemistry.

The ethyl acetate extract from the Streptomyces sp. isolate B8652 delivered the trioxacarcins A to approximately C (2a to approximately 2c) and additionally three new derivatives designated as trioxacarcins D to approximately F (2d to approximately 2f). All trioxacarcins showed high anti-bacterial and some of them high anti-tumor and anti-malaria activity. The structures of the new antibiotics were derived from mass, 1D and 2D NMR spectra and confirmed by comparison of the NMR data with those of known derivatives. The absolute configuration of the trioxacarcins is deduced from the X-ray analysis of gutingimycin (2g) and from the known stereochemistry of the L-trioxacarcinoses A and B.

Fujianmycin C, A bioactive angucyclinone from a marine derived Streptomyces sp. B6219.

From a marine-derived streptomycete, a new bioactive angucyclinone, fujianmycin C (1), has been isolated along with five known, metabolites fujianmycins A (2) and B (3), ochromycinone (4), ochromycinone methyl ether (5), and tetrangulol methyl ether (6). The structure elucidation of fujianmycin C (1) was performed by detailed analysis of data such as 1H, 13C, 1H, 1H COSY, HSQC, HMBC and NOESY spectra. Fujianmycin C (1) exhibited antibacterial activity against Streptomyces viridochromogenes (Tü57).

Nitro derivatives from the Arctic ice bacterium Salegentibacter sp. isolate T436.

Twenty-five aromatic nitro, dinitro and trinitro compounds were isolated in low yields of less than 1 mg l(-1) from a Salegentibacter sp. strain T436 derived from Arctic pack ice. Their structures were elucidated by MS and NMR techniques. Seven of these compounds, namely, 2-hydroxy-3-(4'-hydroxy-3'-nitrophenyl)-propionic acid methyl ester (6), 2-chloro-3- (4'-hydroxy-3'-nitrophenyl)propionic acid methyl ester (7), 3-(4'-hydroxy-3',5'-dinitrophenyl)-propionic acid methyl ester (14), 4'-hydroxy-3',5'-dinitrophenylethylchloride (16), (4'-hydroxy-3',5'-dinitrophenyl)-2-chloropropionic acid methyl ester (17), N-acetyl-3',5'-dinitrotyramine (18) and 2,6-dinitro-4-(2'-nitroethenyl)phenol (19) are new, and five are reported in this study from a natural source for the first time.

An imidazopyridinone and further metabolites from streptomycetes.

Screening and chromatographic analysis of the extracts from the terrestrial streptomycete GW5127 and from the marine Streptomyces sp. isolate B7967 yielded four new metabolites, i.e. 8-ethyl-6,11-dihydroxy-l1-methoxy-naphthacene-5,12-dione (la), 4-acetyl-1,3-dihydro-imidazo[4,5-c]pyridin-2-one (4a), 5-hydroxmethyl-4-hydroxy-2,4-dimethyl-2-cyclopentenone (6), and N-[2-(3'-hydroxy-4'-methoxyphenyl)-ethyl]-acetamide (5a), along with five known compounds, beta-rubromycin (2), rubromycin (3), 2-(3'-hydroxy-4'-methoxyphenyl)ethanol (5b), uracil, and N-acetyltyramine. The structures of the new compounds were deduced from high resolution mass, 1D and 2D NMR spectra and by comparison with related compounds from the literature. The antibiotic activity of the crude extracts was due to 2 and 3.