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Effective treatment and prevention of any disease necessitates knowledge of the causative agent, yet the causative agents of most coral diseases remain unknown, in part due to the difficulty of distinguishing the pathogenic microbe(s) among the complex microbial backdrop of coral hosts. Stony coral tissue loss disease (SCTLD) is a particularly destructive disease of unknown etiology, capable of transmitting through the water column and killing entire colonies within a matter of weeks. Here we used a previously described method to (i) isolate diseased and apparently healthy coral colonies within individual mesocosms containing filtered seawater with low microbial background levels; (ii) incubate for several days to enrich the water with coral-shed microbes; (iii) use tangential-flow filtration to concentrate the microbial community in the mesocosm water; and then (iv) filter the resulting concentrate through a sequential series of different pore-sized filters. To investigate the size class of microorganism(s) associated with SCTLD transmission, we used 0.8 µm pore size filters to capture microeukaryotes and expelled zooxanthellae, 0.22 µm pore size filters to capture bacteria and large viruses, and 0.025 µm pore size filters to capture smaller viruses. In an attempt to further refine which size fraction(s) contained the transmissible element of SCTLD, we then applied these filters to healthy "receiver" coral fragments and monitored them for the onset of SCTLD signs over three separate experimental runs. However, several factors outside of our control confounded the transmission results, rendering them inconclusive. As the bulk of prior studies of SCTLD in coral tissues have primarily investigated the associated bacterial community, we chose to characterize the prokaryotic community associated with all mesocosm 0.22 µm pore size filters using Illumina sequencing of the V4 region of the 16S rRNA gene. We identified overlaps with prior SCTLD studies, including the presence of numerous previously identified SCTLD bioindicators within our mesocosms. The identification in our mesocosms of specific bacterial amplicon sequence variants that also appear across prior studies spanning different collection years, geographic regions, source material, and coral species, suggests that bacteria may play some role in the disease. [ABSTRACT FROM AUTHOR]

The causative agents of most coral diseases today remain unknown, complicating disease response and restoration efforts. Pathogen identifications can be hampered by complex microbial communities naturally associated with corals and seawater, which create complicating "background noise" that can potentially obscure a pathogen's signal. Here, we outline an approach to investigate waterborne coral diseases that use a combination of coral mesocosms, tangential flow filtration, and size fractionation to reduce the impact of this background microbial diversity, compensate for unknown infectious dose, and further narrow the suspect pool of potential pathogens. As proof of concept, we use this method to compare the bacterial communities shed into six Montastraea cavernosa coral mesocosms and demonstrate this method effectively detects differences between diseased and healthy coral colonies. We found several amplicon sequence variants (ASVs) in the diseased mesocosms that represented 100% matches with ASVs identified in prior studies of diseased coral tissue, further illustrating the effectiveness of our approach. Our described method is an effective alternative to using coral tissue or mucus to investigate waterborne coral diseases of unknown etiology and can help more quickly narrow the pool of possible pathogens to better aid in disease response efforts. Additionally, this versatile method can be easily adapted to characterize either the entire microbial community associated with a coral or target-specific microbial groups, making it a beneficial approach regardless of whether a causative agent is suspected or is completely unknown. [ABSTRACT FROM AUTHOR]

Colour variation in marine invertebrates is typically attributed to intraspecific variability; however, the use of molecular tools to investigate its genetic basis has uncovered many instances of cryptic speciation. The colonial ascidian Distaplia bermudensis occurs in a wide array of colour morphs, ranging from all white to a dark blue tunic with yellow siphon apertures; yet careful observations of zooid and larval morphologies have not revealed any consistent difference among these colour morphs. In this study, we sampled the 5 main colour morph groupings of D. bermudensis from Wilmington, North Carolina (USA) and sequenced fragments of the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear 18S rRNA genes. Analyses of both genes revealed the presence of two distinct genetic lineages that corresponded to unique colour morphology groupings. We further characterized symbiotic microbial communities for four samples from each lineage by high‐throughput sequencing of partial 16S rRNA genes. Each genetic lineage also harboured unique symbiont communities that differed significantly in diversity and structure. Thus, the two genetic lineages detected herein corresponded to unique colour morphs and microbial communities, indicating that two distinct species coexist under the same scientific name. Further, our study reports the utility of symbiont profiling in resolving the taxonomic status of phenotypically variable ascidian species. [ABSTRACT FROM AUTHOR]

The article presents an organizational biology research study investigating the cause of a recent mass mortality event of the sea urchin Diadema antillarum in the Caribbean Sea. Topics include identifying a scuticociliate to Philaster apodigitiformis consistently associated with abnormal urchins at affected sites; and researchers fulfilled Koch's postulates, confirming the scuticociliate's role in the mortality event and terming the condition D. antillarum scuticociliatosis.

Giant barrel sponges (GBSs) belong to a cryptic species complex (Xestospongia spp.) and are found on tropical reefs worldwide. Over their range, including most of the Caribbean, GBSs have a cylindrical shape, with variation in height, diameter and surface complexity. However, off the southwest coast of Barbados, GBSs mostly exhibit a clam shape or a tub shape, interspersed with a few that have the normal barrel morphotype, suggesting that this variation is not due to environmental factors. Haplotype identification (mtDNA-COI) of six clam and six normal sponges indicated no clear genetic differentiation based on morphotype; hence, this morphological variation remains unexplained. [ABSTRACT FROM AUTHOR]

1H-NMR and circular dichroism studies have been carried out on osteocalcin, a 49-residue, calcium-binding protein, the sequence of which contains a disulphide bridge, a proline-rich segment and three γ-carboxyglutamic acid (Gla) residues. These latter residues have been proposed to lie on one face of an alpha helix and interact with the mineral phase, leading to incorporation of the protein into the bone matrix. Circular dichroism shows an increase in the alpha-helical structure on Ca2+ binding to bovine osteocalcin. This induced structure is lost on heating the protein, giving a spectrum close to that of the Ca2+-free protein. 1H-NMR studies of rabbit osteocalcin gave a set of resonance assignments and NOEs which could be interpreted in terms of distance constraints. These did not allow a single conformation to be defined for the protein in solution but reflect rather a flexible structure which may be essential for the function of the protein. The calculated structures contain a hydrophobic core (comprising Leu2, Leu32, Val36 and Tyr42, seen to be slowly flipping in the Ca2+-bound form) and have the γ-carboxyglutamic acid side chains exposed on one face of the molecule. [ABSTRACT FROM AUTHOR]

Using NMR spectroscopy to visualise tyrosine phosphorylation kinetics in real time, we have investigated the sequence-dependent determinants of the selectivity of the human insulin receptor protein-tyrosine kinase for different tyrosine residues. The peptides used encompass the multipletyrosine-containing autophosphorylation site sequences from the itisulin receptor kinase core domain (Tyr1158, Tyr1162 and Tyr1163) and from its specific C-terminal tail domain (Tyr1328 and Tyr1334). Comparison of the phosphorylation kinetics with those found for the tyrosine residues on a peptide comprising the regulatory tyrosine phosphorylation site of cdc2 points to the role of the primary sequence context of the phosphate acceptor. The particularly deleterious influence of a basic residue immediately C-terminal to the tyrosine is discussed in relation to the autophosphorylation properties of the regulatory loop regions of the insulin and epidermal growth factor receptor kinases. The data further suggest that receptor tyrosine kinase active sites and their substrate targets act in concert to ensure that specific downstream effects are activated. [ABSTRACT FROM AUTHOR]