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Kahalalides, originally isolated from the sacoglossan mollusk Elysia rufescens , have been found in various Elysia and Bryopsis species, with over 20 variants identified to date. These compounds are biosynthesized by Candidatus Endobryopsis kahalalidefaciens within Bryopsis species. In this study, we report the isolation and structural determination of a new cyclic depsipeptide, mebamamide C (1), from Bryopsis sp. The planar structure was determined by spectroscopic data analyses, and the absolute configurations were determined using Marfey's method and modified Mosher's method. Additionally, our study explores the chemical relationship between Bryopsis algae and Elysia mollusks. The individual chemical profiles of these marine organisms highlight a fascinating aspect of marine chemical ecology. The distinct, species-specific chemical profiles observed in Elysia species imply the possibility of a symbiotic relationship with the kahalalide-producing bacteria. [ABSTRACT FROM AUTHOR]

The mesopelagic calanoid copepod Cephalophanes reflugens is characterized by its large eyes with semi-parabolic reflectors. It is hypothesized that the eyes aid in finding crustacean carcasses as food in poor deep-sea light and oligotrophic conditions. Here, the crustacean carcasses-associated luminous, chitin-degrading bacteria may play a vital role in detecting and digesting foods by the copepod. In this study, we collected adult female C. reflugens (n  = 9) from the mesopelagic layers off southwestern Japan in the Pacific Ocean and obtained a total of 47 bacterial isolates from the gut contents. None of the isolates were luminescent, but almost half of the isolates were chitinolytic. Based on the 16S rRNA gene sequences, these chitinolytic bacteria were identified as members of the genus Vibrio , Photobacterium and Pseudoalteromonas. In culture experiments at 15°C, most of the chitinolytic isolates efficiently utilized colloidal chitin as the sole carbon source and degraded the carapace strip of shrimp (Litopenaeus vannamei). Some isolates showed these chitinoclastic activities even at low temperatures (<5°C), equivalent to that of the deep-sea waters. The present results imply that chitin-degrading bacteria significantly contribute to chitin digestion in the gut of C. reflugens , whereas the involvement of luminous bacteria in the feeding mechanism remains unidentified. [ABSTRACT FROM AUTHOR]

Cultivated bacteria such as actinomycetes are a highly useful source of biomedically important natural products. However, such 'talented' producers represent only a minute fraction of the entire, mostly uncultivated, prokaryotic diversity. The uncultured majority is generally perceived as a large, untapped resource of new drug candidates, but so far it is unknown whether taxa containing talented bacteria indeed exist. Here we report the single-cell- and metagenomics-based discovery of such producers. Two phylotypes of the candidate genus 'Entotheonella' with genomes of greater than 9 megabases and multiple, distinct biosynthetic gene clusters co-inhabit the chemically and microbially rich marine sponge Theonella swinhoei. Almost all bioactive polyketides and peptides known from this animal were attributed to a single phylotype. 'Entotheonella' spp. are widely distributed in sponges and belong to an environmental taxon proposed here as candidate phylum 'Tectomicrobia'. The pronounced bioactivities and chemical uniqueness of 'Entotheonella' compounds provide significant opportunities for ecological studies and drug discovery., More than half of the known natural products with antimicrobial, antitumour or antiviral activity are of bacterial origin (1). Most of these compounds were isolated from cultivated representatives of only [...]

X-ray single-crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals. Here we report a protocol for SCD analysis that does not require the crystallization of the sample. In our method, tiny crystals of porous complexes are soaked in a solution of the target, such that the complexes can absorb the target molecules. Crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks. Because the SCD analysis is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram-microgram order. We demonstrate that as little as about 80 nanograms of a sample is enough for the SCD analysis. In combination with high-performance liquid chromatography, our protocol allows the direct characterization of multiple fractions, establishing a prototypical means of liquid chromatography SCD analysis. Furthermore, we unambiguously determined the structure of a scarce marine natural product using only 5 micrograms of the compound., Chemists need reliable methods to analyse and determine molecular structures. Nuclear magnetic resonance (NMR) and mass spectrometry are indispensable tools in daily chemical research for rapidly analysing molecular structures, but, [...]