Isolation,structure determination and cytotoxicity studies of tryptophan alkaloids from an Australian marine sponge Hyrtios sp.

Mass-guided fractionation of the MeOH extract from a specimen of the Australian marine sponge Hyrtios sp. resulted in the isolation of two new tryptophan alkaloids, 6-oxofascaplysin (2), and secofascaplysic acid (3), in addition to the known metabolites fascaplysin (1) and reticulatate (4). The structures of all molecules were determined following NMR and MS data analysis. Structural ambiguities in 2 were addressed through comparison of experimental and DFT-generated theoretical NMR spectral values. Compounds 1–4 were evaluated for their cytotoxicity against a prostate cancer cell line (LNCaP) and were shown to display IC₅₀ values ranging from 0.54 to 44.9 μM.     

3D,Mutually Embedded MOF@Carbon Nanotube Hybrid Networks for High‐Performance Lithium‐Sulfur Batteries

Metal‐organic frameworks (MOFs) hybridized with a conductive matrix could potentially serve as a sulfur host for lithium‐sulfur (Li‐S) battery electrodes; so far most of the previously studied hybrid structures are in the powder form or thin compact films. This study reports 3D porous MOF@carbon nanotube (CNT) networks by grafting MOFs with tailored particle size uniformly throughout a CNT sponge skeleton. Growing larger‐size MOF particles to entrap the conductive CNT network yields a mutually embedded structure with high stability, and after sulfur encapsulation, it shows an initial discharge capacity of ≈1380 mA h g^?1 (at 0.1 C) and excellent cycling stability with a very low fading rate. Furthermore, owing to the 3D porous network that is suitable for enhanced sulfur loading, a remarkable areal capacity of ≈11 mA h cm^?2 (at 0.1 C) is obtained, which is much higher than other MOF‐based hybrid electrodes. The mutually embedded MOF@CNTs with simultaneously high specific capacity, areal capacity, and cycling stability represent an advanced candidate for developing high‐performance Li‐S batteries and other energy storage systems.     

Evolution and function of eukaryotic‐like proteins from sponge symbionts

Sponges (Porifera) are ancient metazoans that harbour diverse microorganisms, whose symbiotic interactions are essential for the host's health and function. Although symbiosis between bacteria and sponges are ubiquitous, the molecular mechanisms that control these associations are largely unknown. Recent (meta‐) genomic analyses discovered an abundance of genes encoding for eukaryotic‐like proteins (ELPs) in bacterial symbionts from different sponge species. ELPs belonging to the ankyrin repeat (AR) class from a bacterial symbiont of the sponge Cymbastela concentrica were subsequently found to modulate amoebal phagocytosis. This might be a molecular mechanism, by which symbionts can control their interaction with the sponge. In this study, we investigated the evolution and function of ELPs from other classes and from symbionts found in other sponges to better understand the importance of ELPs for bacteria–eukaryote interactions. Phylogenetic analyses showed that all of the nine ELPs investigated were most closely related to proteins found either in eukaryotes or in bacteria that can live in association with eukaryotes. ELPs were then recombinantly expressed in Escherichia coli and exposed to the amoeba Acanthamoeba castellanii, which is functionally analogous to phagocytic cells in sponges. Phagocytosis assays with E. coli containing three ELP classes (AR, TPR‐SEL1 and NHL) showed a significantly higher percentage of amoeba containing bacteria and average number of intracellular bacteria per amoeba when compared to negative controls. The result that various classes of ELPs found in symbionts of different sponges can modulate phagocytosis indicates that they have a broader function in mediating bacteria–sponge interactions.     

Sterol-dependent membrane association of the marine sponge-derived bicyclic peptide Theonellamide A as examined by 1H NMR

Theonellamide A (TNM-A) is an antifungal bicyclic dodecapeptide isolated from a marine sponge Theonella sp. Previous studies have shown that TNM-A preferentially binds to 3β-hydroxysterol-containing membranes and disrupts membrane integrity. In this study, several ¹H NMR-based experiments were performed to investigate the interaction mode of TNM-A with model membranes. First, the aggregation propensities of TNM-A were examined using diffusion ordered spectroscopy; the results indicate that TNM-A tends to form oligomeric aggregates of 2–9 molecules (depending on peptide concentration) in an aqueous environment, and this aggregation potentially influences the membrane-disrupting activity of the peptide. Subsequently, we measured the ¹H NMR spectra of TNM-A with sodium dodecyl sulfate-d₂₅ (SDS-d₂₅) micelles and small dimyristoylphosphatidylcholine (DMPC)-d₅₄/dihexanoylphosphatidylcholine (DHPC)-d₂₂ bicelles in the presence of a paramagnetic quencher Mn²⁺. These spectra indicate that TNM-A poorly binds to these membrane mimics without sterol and mostly remains in the aqueous media. In contrast, broader ¹H signals of TNM-A were observed in 10 mol % cholesterol-containing bicelles, indicating that the peptide efficiently binds to sterol-containing bilayers. The addition of Mn²⁺ to these bicelles also led to a decrease in the relative intensity and further line-broadening of TNM-A signals, indicating that the peptide stays near the surface of the bilayers. A comparison of the relative signal intensities with those of phospholipids showed that TNM-A resides in the lipid–water interface (close to the C2′ portion of the phospholipid acyl chain). This shallow penetration of TNM-A to lipid bilayers induces an uneven membrane curvature and eventually disrupts membrane integrity. These results shed light on the atomistic mechanism accounting for the membrane-disrupting activity of TNM-A and the important role of cholesterol in its mechanism of action.     

New antibacterial sesquiterpene aminoquinones from a Vietnamese marine sponge of Spongia sp.

Two new sesquiterpene aminoquinones, langcoquinones A (1) and B (2), together with seven known meroterpenoids (3⿿9), were isolated from the marine sponge Spongia sp. collected in Vietnam. Their structures were determined on the basis of spectroscopic analyses and comparisons with published data. The antibacterial activities of the isolated compounds (1⿿9) were investigated against four bacterial strains. Among these, the new sesquiterpene aminoquinones (1 and 2) and the known related compounds (3, 5, 6, 8, and 9) exhibited significant antibacterial activities against Staphylococcus aureus and Bacillus subtilis, with MICs ranging from 6.25 to 12.5 μM.     

Nutrient translocation from green algal symbionts to the freshwater sponge Ephydatia fluviatilis

The symbiosis between the freshwater sponge Ephydatia fluviatilis and a chlorella-like green alga is not obligate and only occurs when the sponge grows in the light. The algae accumulate intracellular pools of sucrose and glucose and translocate between 9 and 17% of the total photosynthate to the host. The principal product translocated is glucose which is fed directly into the sponge metabolic pool. White sponges transplanted back into the river in the shade grew logarithmically with a mean doubling time of 12 days. Sponges transplanted into illuminated habitats did not grow. It is unknown how the sponge acquires its algal symbiont.