Viral ecogenomics across the Porifera

BackgroundViruses directly affect the most important biological processes in the ocean via their regulation of prokaryotic and eukaryotic populations. Marine sponges form stable symbiotic partnerships with a wide diversity of microorganisms and this high symbiont complexity makes them an ideal model for studying viral ecology. Here, we used morphological and molecular approaches to illuminate the diversity and function of viruses inhabiting nine sponge species from the Great Barrier Reef and seven from the Red Sea.ResultsViromic sequencing revealed host-specific and site-specific patterns in the viral assemblages, with all sponge species dominated by the bacteriophage order Caudovirales but also containing variable representation from the nucleocytoplasmic large DNA virus families Mimiviridae, Marseilleviridae, Phycodnaviridae, Ascoviridae, Iridoviridae, Asfarviridae and Poxviridae. Whilst core viral functions related to replication, infection and structure were largely consistent across the sponge viromes, functional profiles varied significantly between species and sites largely due to differential representation of putative auxiliary metabolic genes (AMGs) and accessory genes, including those associated with herbicide resistance, heavy metal resistance and nylon degradation. Furthermore, putative AMGs varied with the composition and abundance of the sponge-associated microbiome. For instance, genes associated with antimicrobial activity were enriched in low microbial abundance sponges, genes associated with nitrogen metabolism were enriched in high microbial abundance sponges and genes related to cellulose biosynthesis were enriched in species that host photosynthetic symbionts.ConclusionsOur results highlight the diverse functional roles that viruses can play in marine sponges and are consistent with our current understanding of sponge ecology. Differential representation of putative viral AMGs and accessory genes across sponge species illustrate the diverse suite of beneficial roles viruses can play in the functional ecology of these complex reef holobionts

Helium suicide, a rapid and painless asphyxia: toxicological findings.

Suicide by helium inhalation has become increasingly common in the last few decades in Europe and the US because it produces a quick and painless death. Inhaled-gas suicides can easily be assessed through death scene investigation and autopsy. However, helium is a colorless and odorless inert gas that unfortunately cannot be detected using standard toxicological analysis. A successful gas analysis was performed following the suicide of a 17-year-old female. For the detection of helium, central/peripheral blood samples and gaseous samples from the esophagus, stomach, and upper and lower respiratory airways (from the trachea and the primary left and right bronchia) were collected with a gastight syringe, ensuring minimal dilution. Qualitative analyses were positive in all gaseous samples. Quantitative analyses were performed using a special gas-inlet system with a vacuum by which the sample can be transferred to a mass spectrometer, reducing the risk of contamination. Helium concentrations were 20.16% from the trachea, 12.33% from the right lung, and 1.5% from the stomach. Based on the high levels of helium, the cause and manner of death were assessed as asphyxia suicide by inhalation of helium. Therefore, toxicological analyses should always be applied in order to gain evidence of inhaled gas in gaseous samples

Biophysical Characterization of Refolded Drosophila Spatzle, a Cystine Knot Protein, Reveals Distinct Properties of Three Isoforms

The Drosophila Spätzle protein, involved in the embryonic development of the dorsal ventral axis and in the adult immune response, is expressed as a proprotein and is activated by the serine proteinases Easter or Spätzle processing enzyme. Proteolytic cleavage generates a 106 amino acid COOH terminal fragment, C106, homologous to the mature form of nerve growth factor NGF, a cystine knot protein. Through alternative splicing, the Spätzle gene encodes for several isoforms that with one exception, the propeptide isoform share C106 but differ in the prosequence. Three isoforms have been expressed recombinantly in Escherichia coli strains. The propeptide isoform could be expressed in soluble form and is unstructured according to CD and NMR measurements. Dimeric full length Spätzle isoforms have been refolded from insoluble inclusion bodies and are able to rescue Spätzle deficient embryos. Although the two full length isoforms exhibit similar far UV CD spectra, large differences in tryptophan fluorescence quenching by the respective pro parts are observed. Both full length isoforms exhibited highly cooperative folding transitions. Proteolytic digestion using trypsin resulted in C106, whose unfolding exhibits lower thermodynamic stability and cooperativity compared with the full length proteins. The structure of C106 reveals a T shaped dimer with significant differences to NGF and a deep internal cavity. Substantial amp; 946; sheet formation is observed between the two monomers, whereas a long loop containing the single tryptophan residue is disordered in the crystals. Our results suggest that the propeptides stabilize the tertiary structure of the mature Spätzle cystine kno