Natural Asphalt Seeps Are Potential Sources for Recalcitrant Oceanic Dissolved Organic Sulfur and Dissolved Black Carbon.

Natural oil seepages contribute about one-half of the annual petroleum input to marine systems. Yet, environmental implications and the persistence of water-soluble hydrocarbons from these seeps are vastly unknown. We investigated the release of oil-derived dissolved organic matter (DOM) from natural deep sea asphalt seeps using laboratory incubation experiments. Fresh asphalt samples collected at the Chapopote asphalt volcano in the Southern Gulf of Mexico were incubated aerobically in artificial seawater over 4 weeks. The compositional changes in the water-soluble fraction of asphalt-derived DOM were determined with ultrahigh-resolution mass spectrometry (Fourier-transform ion cyclotron resonance mass spectrometry, FT-ICR-MS) and by excitation-emission matrix spectroscopy to characterize fluorescent DOM (FDOM) applying parallel factor (PARAFAC) analysis. Highly reduced aliphatic asphalt-derived DOM was readily biodegraded, while aromatic and sulfur-enriched DOM appeared to be less bioavailable and accumulated in the aqueous phase. A quantitative molecular tracer approach revealed the abundance of highly condensed aromatic molecules of thermogenic origin. Our results indicate that natural asphalt and potentially other petroleum seepages can be sources of recalcitrant dissolved organic sulfur and dissolved black carbon to the ocean.

Activation of the NLRP3 Inflammasome by Hyaboron, a New Asymmetric Boron-Containing Macrodiolide from the Myxobacterium Hyalangium minutum.

A Natural Compound Library containing myxobacterial secondary metabolites was screened in murine macrophages for novel activators of IL-1ß maturation and secretion. The most potent of three hits in total was a so far undescribed metabolite, which was identified from the myxobacterium Hyalangium minutum strain Hym3. While the planar structure of 1 was elucidated by high resolution mass spectrometry and NMR data yielding an asymmetric boron containing a macrodiolide core structure, its relative stereochemistry of all 20 stereocenters of the 42-membered ring was assigned by rotating frame Overhause effect spectroscopy correlations, 1H,1H, and 1H,13C coupling constants, and by comparison of 13C chemical shifts to those of the structurally related metabolites tartrolon B-D. The absolute stereochemistry was subsequently assigned by Mosher's and Marfey's methods. Further functional studies revealed that hyaboron and other boronated natural compounds resulted in NLRP3 inflammasome dependent IL-1ß maturation, which is most likely due to their ability to act as potassium ionophores. Moreover, besides its inflammasome-stimulatory activity in human and mouse cells, hyaboron (1) showed additional diverse biological activities, including antibacterial and antiparasitic effects.

The Exometabolome of Two Model Strains of the Roseobacter Group: A Marketplace of Microbial Metabolites.

Recent studies applying Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) showed that the exometabolome of marine bacteria is composed of a surprisingly high molecular diversity. To shed more light on how this diversity is generated we examined the exometabolome of two model strains of the Roseobacter group, Phaeobacter inhibens and Dinoroseobacter shibae, grown on glutamate, glucose, acetate or succinate by FT-ICR-MS. We detected 2,767 and 3,354 molecular formulas in the exometabolome of each strain and 67 and 84 matched genome-predicted metabolites of P. inhibens and D. shibae, respectively. The annotated compounds include late precursors of biosynthetic pathways of vitamins B1, B2, B5, B6, B7, B12, amino acids, quorum sensing-related compounds, indole acetic acid and methyl-(indole-3-yl) acetic acid. Several formulas were also found in phytoplankton blooms. To shed more light on the effects of some of the precursors we supplemented two B1 prototrophic diatoms with the detected precursor of vitamin B1 HET (4-methyl-5-(ß-hydroxyethyl)thiazole) and HMP (4-amino-5-hydroxymethyl-2-methylpyrimidine) and found that their growth was stimulated. Our findings indicate that both strains and other bacteria excreting a similar wealth of metabolites may function as important helpers to auxotrophic and prototrophic marine microbes by supplying growth factors and biosynthetic precursors.