Search

The organic carbon (Corg) stored in seagrass meadows is globally significant and could be relevant in strategies to mitigate increasing CO2 concentration in the atmosphere. Most of that stored Corg is in the soils that underlie the seagrasses. We explored how seagrass and soil characteristics vary among seagrass meadows across the geographic range of turtlegrass (Thalassia testudinum) with a goal of illuminating the processes controlling soil organic carbon (Corg) storage spanning 23° of latitude. Seagrass abundance (percent cover, biomass, and canopy height) varied by over an order of magnitude across sites, and we found high variability in soil characteristics, with Corg ranging from 0.08 to 12.59% dry weight. Seagrass abundance was a good predictor of the Corg stocks in surficial soils, and the relative importance of seagrass-derived soil Corg increased as abundance increased. These relationships suggest that first-order estimates of surficial soil Corg stocks can be made by measuring seagrass abundance and applying a linear transfer function. The relative availability of the nutrients N and P to support plant growth was also correlated with soil Corg stocks. Stocks were lower at N-limited sites than at P-limited ones, but the importance of seagrass-derived organic matter to soil Corg stocks was not a function of nutrient limitation status. This finding seemed at odds with our observation that labile standard substrates decomposed more slowly at N-limited than at P-limited sites, since even though decomposition rates were 55% lower at N-limited sites, less Corg was accumulating in the soils. The dependence of Corg stocks and decomposition rates on nutrient availability suggests that eutrophication is likely to exert a strong influence on carbon storage in seagrass meadows.

Black band disease is a globally distributed and easily recognizable coral disease. Despite years of study, the etiology of this coral disease, which impacts dozens of stony coral species, is not completely understood. Although black band disease mats are predominantly composed of the cyanobacterial species Roseofilum reptotaenium, other filamentous cyanobacterial strains and bacterial heterotrophs are readily detected. Through chemical ecology and metagenomic sequencing, we uncovered cryptic strains of Roseofilum species from Siderastrea siderea corals that differ from those on other corals in the Caribbean and Pacific. Isolation of metabolites from Siderastrea-derived Roseofilum revealed the prevalence of unique forms of looekeyolides, distinct from previously characterized Roseofilum reptotaenium strains. In addition, comparative genomics of Roseofilum strains showed that only Siderastrea-based Roseofilum strains have the genetic capacity to produce lasso peptides, a family of compounds with diverse biological activity. All nine Roseofilum strains examined here shared the genetic capacity to produce looekeyolides and malyngamides, suggesting these compounds support the ecology of this genus. Similar biosynthetic gene clusters are not found in other cyanobacterial genera associated with black band disease, which may suggest that looekeyolides and malyngamides contribute to disease etiology through yet unknown mechanisms.

Naturally produced polybrominated diphenyl ethers (PBDEs) pervade the marine environment and structurally resemble toxic man-made brominated flame retardants. PBDEs bioaccumulate in marine animals and are likely transferred to the human food chain. However, the biogenic basis for PBDE production in one of their most prolific sources, marine sponges of the order Dysideidae, remains unidentified. Here, we report the discovery of PBDE biosynthetic gene clusters within sponge-microbiome-associated cyanobacterial endosymbionts through the use of an unbiased metagenome-mining approach. Using expression of PBDE biosynthetic genes in heterologous cyanobacterial hosts, we correlate the structural diversity of naturally produced PBDEs to modifications within PBDE biosynthetic gene clusters in multiple sponge holobionts. Our results establish the genetic and molecular foundation for the production of PBDEs in one of the most abundant natural sources of these molecules, further setting the stage for a metagenomic-based inventory of other PBDE sources in the marine environment.

Tetrabromopyrrole (TBP) is a readily biosynthesized marine proteobacterial compound that induces coral settlement (attachment and metamorphosis) at concentrations ranging from 50 - 250 ng ml-1 (0.13 - 0.65 μM). This suggests a great potential for the use of this compound as a settlement inducer for restoration purposes. However, the applicability and optimal concentration of TBP for many coral species is not yet known. Furthermore, TBP is an unstable compound, which may present both challenges and benefits to its potential use for restoration purposes. In order to assess the utility of this compound for restoration, settlement induction by TBP was assessed among a wide range of Caribbean coral species. Additionally, a suite of halogenated compounds (tribromopyrrole, pentabromopseudolin, dibromophenol, tribromophenol, bromophene, n-methyl tetrabromopyrrole, tetrachloropyrrole, dibromoindole, n-methyl tetrachloropyrrole and dibromopyridine) that are related to TBP, some of which have similar antibiotic and antialgal properties, were also tested for settlement induction activity. These compounds were chosen based on their structural similarity to TBP or their identity as a product within the bacterial TBP biosynthetic pathway. TBP induced settlement in nine of ten coral species tested including seven not previously reported (Dendrogyra cylindrus, Orbicella faveolata, Colpophyllia natans, Diploria labyrinthiformis, Pseudodiploria clivosa, Acropora cervicornis, Montastraea cavernosa) at concentrations ranging from 0.375 - 1.5 μM. No other compound tested induced settlement, demonstrating a high degree of specificity for TBP. [ABSTRACT FROM AUTHOR]

NMR and MS/MS-based metabolomics of a cyanobacterial extract from Piti Bomb Holes, Guam, indicated the presence of unique enyne-containing halogenated fatty acid amides. We isolated three new compounds of this class, taveuniamides L-N (1–3), along with the previously reported taveuniamide F (4), which was the most abundant analog. The planar structures of the new compounds were established using 1D and 2D NMR as well as mass spectrometry. We established the configuration of this chemical class to be R at C-8 via Mosher's analysis of 4 after reduction of the carboxamide group. Our biological investigations with 4 revealed that the compound binds to the cannabinoid receptor CNR1, acting as an antagonist/inverse agonist in the canonical G-protein signaling pathways. In selectivity profiling against 168 GPCR targets using the β-arrestin functional assay, we found that 4 antagonizes GPR119, NPSR1b, CCR9, CHRM4, GPR120, HTR2A, and GPR103, in addition to CNR1. Interestingly, 4 showed a 6.8-fold selectivity for CNR1 over CNR2. The binding mode of 4 to CNR1 was investigated using docking and molecular dynamics simulations with both natural and unnatural stereoisomers, revealing important CNR1 residues for the interaction and also providing a possible reasoning for the observed CNR1/CNR2 selectivity. [ABSTRACT FROM AUTHOR]

This work was undertaken to evaluate the biological activity of the aqueous extract of the dry seeds of Aframomum daniellii seeds on the copulatory performance of rats with testicular deficiency.Hypogonadal adult male rats (30) were divided into 6 groups: group I received distilled water (10 ml/kg), group II received sildenafil citrate (5 mg/kg), group III received intramuscular injections of testosterone enanthate (3. 6 mg/kg), group IV, V, and VI received the aqueous extract of A. daniellii at the respective doses of 100, 200, and 400 mg/kg/po/day for 14 days. The copulatory performance of the animals were assessed on days 1, 7 and 14 through the following copulation parameters: Mount, intromission, and ejaculation latency (ML, IL, and EL) and frequency (MF, IF and EF), average interval of copulation (AIC) and post-ejaculatory interval (PEI)). We noticed a significant decrease of ML (p < 0.05), IL (p < 0.01), EL (p < 0.001) and the increase of MF, IF and EF (p < 0.01) particularly at doses of 100 and 400 mg/kg when compared to group I and II. In addition, we noticed a significant increase of AIC from day 7 (p < 0.05) to day 14 (p < 0.001) at the same two doses while the PEI significantly decreased from the 1st (p < 0.01) to the 14th day (p < 0.001) when compared to group I and II. These findings demonstrated that A. daniellii aqueous extract of seeds enhanced pro-sexual potential and pro-sexual desire in male rats with testicular deficiency.

The monounsaturated fatty acid 7(E)-9-keto-hexadec-7-enoic acid (1) and three structurally related analogues with different oxidation states and degrees of unsaturation (2–4) were discovered from a marine benthic cyanobacterial mat collected from Delta Shoal, Florida Keys. Their structures were elucidated using NMR spectroscopy and mass spectrometry. The structure of 1 contained an α,β-unsaturated carbonyl system, a key motif required for the activation of the Keap1/Nrf2−ARE pathway that is involved in the activation of antioxidant and phase II detoxification enzymes. Compounds 1–4 were screened in ARE-luciferase reporter gene assay using stably transfected HEK293 cells, and only 1 significantly induced Nrf2 activity at 32 and 10 µM, whereas 2–4 were inactive. As there is crosstalk between inflammation and oxidative stress, subsequent biological studies were focused on 1 to investigate its anti-inflammatory potential. Compound 1 induced Nqo1, a well-known target gene of Nrf2, and suppressed iNos transcript levels, which translated into reduced levels of nitric oxide in LPS-activated mouse macrophage RAW264.7 cells, a more relevant model for inflammation. RNA sequencing was performed to capture the effects of 1 on a global level and identified additional canonical pathways and upstream regulators involved in inflammation and immune response, particularly those related to multiple sclerosis. A targeted survey of marine cyanobacterial samples from other geographic locations, including Guam, suggested the widespread occurrence of 1. Furthermore, the previous isolation of 1 from marine diatoms and green algae implied a potentially important ecological role across marine algal eukaryotes and prokaryotes. The previous isolation from sea lettuce raises the possibility of dietary intervention to attenuate inflammation and related disease progression. [ABSTRACT FROM AUTHOR]