Common fear molecules induce defensive responses in marine prey across trophic levels.

Predator-prey interactions are a key feature of ecosystems and often chemically mediated, whereby individuals detect molecules in their environment that inform whether they should attack or defend. These molecules are largely unidentified, and their discovery is important for determining their ecological role in complex trophic systems. Homarine and trigonelline are two previously identified blue crab (Callinectes sapidus) urinary metabolites that cause mud crabs (Panopeus herbstii) to seek refuge, but it was unknown whether these molecules influence other species within this oyster reef system. In the current study, homarine, trigonelline, and blue crab urine were tested on juvenile oysters (Crassostrea virginica) to ascertain if the same molecules known to alter mud crab behavior also affect juvenile oyster morphology, thus mediating interactions between a generalist predator, a mesopredator, and a basal prey species. Oyster juveniles strengthened their shells in response to blue crab urine and when exposed to homarine and trigonelline in combination, especially at higher concentrations. This study builds upon previous work to pinpoint specific molecules from a generalist predator's urine that induce defensive responses in two marine prey from different taxa and trophic levels, supporting the hypothesis that common fear molecules exist in ecological systems.

Isolation and Characterization of Anti-Mycobacterial Natural Products from a Petrosia sp. Marine Sponge.

Tuberculosis (TB) is a dreadful infectious disease and a leading cause of mortality and morbidity worldwide, second in 2020 only to severe acute respiratory syndrome 2 (SARS-Cov-2). With limited therapeutic options available and a rise in multidrug-resistant tuberculosis cases, it is critical to develop antibiotic drugs that display novel mechanisms of action. Bioactivity-guided fractionation employing an Alamar blue assay for Mycobacterium tuberculosis strain H37Rv led to the isolation of duryne (13) from a marine sponge Petrosia sp. sampled in the Solomon Islands. Additionally, five new strongylophorine meroditerpene analogues (1-5) along with six known strongylophorines (6-12) were isolated from the bioactive fraction and characterized using MS and NMR spectroscopy, although only 13 exhibited antitubercular activity.

Chemical ecology of the marine plankton.

Covering: January 2015 through December 2017 This review focuses on recent studies on the chemical ecology of planktonic marine ecosystems, with the objective of presenting a comprehensive overview of new findings in the field in the time period covered. In order to highlight the role of chemically mediated interactions in the marine plankton this review has been organized by ecological concepts starting with intraspecific communication, followed by interspecific interactions (including facilitation and mutualism, host-parasite, allelopathy, and predator-prey), and finally the effects of plankton secondary metabolites on community and ecosystem-wide interactions.

The role of extended Fe4S4 cluster ligands in mediating sulfite reductase hemoprotein activity.

The siroheme-containing subunit from the multimeric hemoflavoprotein NADPH-dependent sulfite reductase (SiR/SiRHP) catalyzes the six electron-reduction of SO32- to S2-. Siroheme is an iron-containing isobacteriochlorin that is found in sulfite and homologous siroheme-containing nitrite reductases. Siroheme does not work alone but is covalently coupled to a Fe4S4 cluster through one of the cluster's ligands. One long-standing hypothesis predicted from this observation is that the environment of one iron-containing cofactor influences the properties of the other. We tested this hypothesis by identifying three amino acids (F437, M444, and T477) that interact with the Fe4S4 cluster and probing the effect of altering them to alanine on the function and structure of the resulting enzymes by use of activity assays, X-ray crystallographic analysis, and EPR spectroscopy. We showed that F437 and M444 gate access for electron transfer to the siroheme-cluster assembly and the direct hydrogen bond between T477 and one of the cluster sulfides is important for determining the geometry of the siroheme active site.

Structural and Optical Properties of Sb-Substituted BiSI Grown from Sulfur/Iodine Flux.

Bismuth and antimony were reacted in sulfur/iodine flux mixtures at various temperatures and iodine concentrations to explore the effects of these variables on the synthesis and properties of Bi1-xSbxSI products. The products grow as crystals; microprobe elemental analysis and UV/vis/NIR spectroscopy of the Bi1-xSbxSI solid solutions indicate that substitution is homogeneous within individual crystals but varies up to 15% between crystals within each synthesis batch. Raman spectra show a two-mode behavior upon substitution, indicating covalent bonding within the structure, and TEM/SEM data confirm no presence of nanoclustering or segregation within the crystals.