Season, but not symbiont state, drives microbiome structure in the temperate coral Astrangia poculata.

BACKGROUND: Understanding the associations among corals, their photosynthetic zooxanthella symbionts (Symbiodinium), and coral-associated prokaryotic microbiomes is critical for predicting the fidelity and strength of coral symbioses in the face of growing environmental threats. Most coral-microbiome associations are beneficial, yet the mechanisms that determine the composition of the coral microbiome remain largely unknown. Here, we characterized microbiome diversity in the temperate, facultatively symbiotic coral Astrangia poculata at four seasonal time points near the northernmost limit of the species range. The facultative nature of this system allowed us to test seasonal influence and symbiotic state (Symbiodinium density in the coral) on microbiome community composition. RESULTS: Change in season had a strong effect on A. poculata microbiome composition. The seasonal shift was greatest upon the winter to spring transition, during which time A. poculata microbiome composition became more similar among host individuals. Within each of the four seasons, microbiome composition differed significantly from that of surrounding seawater but was surprisingly uniform between symbiotic and aposymbiotic corals, even in summer, when differences in Symbiodinium density between brown and white colonies are the highest, indicating that the observed seasonal shifts are not likely due to fluctuations in Symbiodinium density. CONCLUSIONS: Our results suggest that symbiotic state may not be a primary driver of coral microbial community organization in A. poculata, which is a surprise given the long-held assumption that excess photosynthate is of importance to coral-associated microbes. Rather, other environmental or host factors, in this case, seasonal changes in host physiology associated with winter quiescence, may drive microbiome diversity. Additional studies of A. poculata and other facultatively symbiotic corals will provide important comparisons to studies of reef-building tropical corals and therefore help to identify basic principles of coral microbiome assembly, as well as functional relationships among holobiont members

Insights into the cultured bacterial fraction of corals

Bacteria associated with coral hosts are diverse and abundant, with recent studies suggesting involvement of these symbionts in host resilience to anthropogenic stress. Despite their putative importance, the work dedicated to culturing coral-associated bacteria has received little attention. Combining published and unpublished data, here we report a comprehensive overview of the diversity and function of culturable bacteria isolated from corals originating from tropical, temperate, and cold-water habitats. A total of 3,055 isolates from 52 studies were considered by our metasurvey. Of these, 1,045 had full-length 16S rRNA gene sequences, spanning 138 formally described and 12 putatively novel bacterial genera across the Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria phyla. We performed comparative genomic analysis using the available genomes of 74 strains and identified potential signatures of beneficial bacterium-coral symbioses among the strains. Our analysis revealed \u3e 400 biosynthetic gene clusters that underlie the biosynthesis of antioxidant, antimicrobial, cytotoxic, and other secondary metabolites. Moreover, we uncovered genomic features-not previously described for coral-bacterium symbioses-potentially involved in host colonization and host-symbiont recognition, antiviral defense mechanisms, and/or integrated metabolic interactions, which we suggest as novel targets for the screening of coral probiotics. Our results highlight the importance of bacterial cultures to elucidate coral holobiont functioning and guide the selection of probiotic candidates to promote coral resilience and improve holistic and customized reef restoration and rehabilitation efforts

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

What Makes Retirees Happier: A Gradual or 'Cold Turkey' Retirement?

This study explores the factors that affect an individual’s happiness while transitioning into retirement. Recent studies highlight gradual retirement as an attractive option to older workers as they approach full retirement. However, it is not clear whether phasing or cold turkey makes for a happier retirement. Using longitudinal data from the Health and Retirement Study, this study explores what shapes the change in happiness between the last wave of full employment and the first wave of full retirement. Results suggest that what really matters is not the type of transition (gradual retirement or cold turkey), but whether people perceive the transition as chosen or forced

Stability, Development, and Function of a Symbiotic Bacterial Community Associated with the Reproductive System of the Hawaiian Bobtail Squid, Euprymna scolopes

Many aquatic organisms deposit their eggs into an environment where successful embryogenesis depends on minimizing biofouling. The female Hawaiian bobtail squid, Euprymna scolopes, harbors a diverse bacterial community within the accessory nidamental gland (ANG), a symbiotic reproductive organ. This community is hypothesized to be environmentally transmitted, and to be deposited from the ANG into the egg jelly coat (JC). Illumina sequencing of the 16S rRNA V4 gene region demonstrated that the ANG bacterial community (n=29) and that of the JC (n=35) were composed primarily of members of the Rhodobacteraceae and Verrucomicrobia, which together comprised on average 86% of the sequences recovered per sample (68% and 18% respectively). JC bacterial communities clustered with the ANG community of the female that produced those eggs, suggesting that bacteria from the ANG are deposited directly into the JC. OTUs representing 94.5% of the average ANG abundance were found in the natural squid environment, consistent with the hypothesis of environmental transmission between generations. The ANG bacterial community gradually changed from a Verrucomicrobia-dominated to an Alphaproteobacteria-dominated community over the course of host sexual development. The surface of the immature ANG was covered in microvilli and contained numerous ciliated invaginations, demonstrating that the immature ANG is poised for colonization by environmental bacteria. Eggs treated with antibiotics over the course of embryogenesis developed a biofilm, primarily composed of the fungus Fusarium keratoplasticum, which led to the death of the embryos (3% viability; n=17 clutches). Fungal challenge experiments on dissected eggs demonstrated that the JC containing the bacterial community is essential for egg defense from fungal bud cells (n=3 trials, 8-10 eggs/treatment). Extracts from ANG/JC bacteria were also able to inhibit F. keratoplasticum in vitro. Taken together, these data suggest that the ANG/JC bacteria protect developing embryos from biofouling. Ongoing work is focused on identifying specific strains and compounds responsible for antifungal activity. This association offers a unique experimental model for understanding mechanisms by which marine invertebrates protect their eggs in the environment. This research has set the background for utilizing the E. scolopes ANG system as a model for studying how consortial symbioses are established and maintained

Season, but not symbiont state, drives microbiome structure in the temperate coral Astrangia poculata

Abstract Background Understanding the associations among corals, their photosynthetic zooxanthella symbionts (Symbiodinium), and coral-associated prokaryotic microbiomes is critical for predicting the fidelity and strength of coral symbioses in the face of growing environmental threats. Most coral-microbiome associations are beneficial, yet the mechanisms that determine the composition of the coral microbiome remain largely unknown. Here, we characterized microbiome diversity in the temperate, facultatively symbiotic coral Astrangia poculata at four seasonal time points near the northernmost limit of the species range. The facultative nature of this system allowed us to test seasonal influence and symbiotic state (Symbiodinium density in the coral) on microbiome community composition. Results Change in season had a strong effect on A. poculata microbiome composition. The seasonal shift was greatest upon the winter to spring transition, during which time A. poculata microbiome composition became more similar among host individuals. Within each of the four seasons, microbiome composition differed significantly from that of surrounding seawater but was surprisingly uniform between symbiotic and aposymbiotic corals, even in summer, when differences in Symbiodinium density between brown and white colonies are the highest, indicating that the observed seasonal shifts are not likely due to fluctuations in Symbiodinium density. Conclusions Our results suggest that symbiotic state may not be a primary driver of coral microbial community organization in A. poculata, which is a surprise given the long-held assumption that excess photosynthate is of importance to coral-associated microbes. Rather, other environmental or host factors, in this case, seasonal changes in host physiology associated with winter quiescence, may drive microbiome diversity. Additional studies of A. poculata and other facultatively symbiotic corals will provide important comparisons to studies of reef-building tropical corals and therefore help to identify basic principles of coral microbiome assembly, as well as functional relationships among holobiont members

Host–symbiont plasticity in the upside-down jellyfish Cassiopea xamachana: strobilation across symbiont genera

IntroductionIn the upside-down jellyfish, Cassiopea xamachana (Cnidaria: Scyphozoa), the establishment of photosymbiosis with dinoflagellates (family Symbiodiniaceae) is necessary for the sessile polyp to undergo metamorphosis (strobilation) into a free-swimming adult. C. xamachana has the capacity to associate with a wide variety of dinoflagellate species and representatives of divergent genera. While some studies have looked at the successful induction of symbiosis, none to date have examined the lasting effect of diverse symbiont taxa on host survivorship and development, which is needed to assess the fitness costs of such symbioses.MethodsOur study exposes C. xamachana polyps to 22 different cultured Symbiodinaceae strains representing 13 species from 5 genera. We analyzed the time to strobilation, the number of ephyra (juvenile medusa) produced, and the proportion of ephyra that died prematurely.ResultsHere we show that C. xamachana strobilation can be induced by nearly each symbiodinacean strain we tested, with the exception of free-living species (i.e., unknown to establish symbiosis with any other marine host). Additionally, ephyrae did not display morphological variation or survivorship differences with varying symbionts. However, we observed intraspecific variation in time to induce strobilation with different cultured dinoflagellate strains.DiscussionThis work expands the known symbiont species that can form stable mutualisms with C. xamachana, primarily in the genera Symbiodinium and Breviolum. Additionally, we provide evidence of differences in ability of cultured symbiodiniaceans to establish symbiosis with a host, which suggests population-level differences in dinoflagellate cultures impact their symbiosis success. By utilizing an animal like C. xamachana with flexible symbiont uptake, we are able to explore how symbiont diversity can influence the timing and success of symbiosis-driven development

Image_1_Host–symbiont plasticity in the upside-down jellyfish Cassiopea xamachana: strobilation across symbiont genera.tif

IntroductionIn the upside-down jellyfish, Cassiopea xamachana (Cnidaria: Scyphozoa), the establishment of photosymbiosis with dinoflagellates (family Symbiodiniaceae) is necessary for the sessile polyp to undergo metamorphosis (strobilation) into a free-swimming adult. C. xamachana has the capacity to associate with a wide variety of dinoflagellate species and representatives of divergent genera. While some studies have looked at the successful induction of symbiosis, none to date have examined the lasting effect of diverse symbiont taxa on host survivorship and development, which is needed to assess the fitness costs of such symbioses.MethodsOur study exposes C. xamachana polyps to 22 different cultured Symbiodinaceae strains representing 13 species from 5 genera. We analyzed the time to strobilation, the number of ephyra (juvenile medusa) produced, and the proportion of ephyra that died prematurely.ResultsHere we show that C. xamachana strobilation can be induced by nearly each symbiodinacean strain we tested, with the exception of free-living species (i.e., unknown to establish symbiosis with any other marine host). Additionally, ephyrae did not display morphological variation or survivorship differences with varying symbionts. However, we observed intraspecific variation in time to induce strobilation with different cultured dinoflagellate strains.DiscussionThis work expands the known symbiont species that can form stable mutualisms with C. xamachana, primarily in the genera Symbiodinium and Breviolum. Additionally, we provide evidence of differences in ability of cultured symbiodiniaceans to establish symbiosis with a host, which suggests population-level differences in dinoflagellate cultures impact their symbiosis success. By utilizing an animal like C. xamachana with flexible symbiont uptake, we are able to explore how symbiont diversity can influence the timing and success of symbiosis-driven development.</p

Table_1_Host–symbiont plasticity in the upside-down jellyfish Cassiopea xamachana: strobilation across symbiont genera.xlsx

IntroductionIn the upside-down jellyfish, Cassiopea xamachana (Cnidaria: Scyphozoa), the establishment of photosymbiosis with dinoflagellates (family Symbiodiniaceae) is necessary for the sessile polyp to undergo metamorphosis (strobilation) into a free-swimming adult. C. xamachana has the capacity to associate with a wide variety of dinoflagellate species and representatives of divergent genera. While some studies have looked at the successful induction of symbiosis, none to date have examined the lasting effect of diverse symbiont taxa on host survivorship and development, which is needed to assess the fitness costs of such symbioses.MethodsOur study exposes C. xamachana polyps to 22 different cultured Symbiodinaceae strains representing 13 species from 5 genera. We analyzed the time to strobilation, the number of ephyra (juvenile medusa) produced, and the proportion of ephyra that died prematurely.ResultsHere we show that C. xamachana strobilation can be induced by nearly each symbiodinacean strain we tested, with the exception of free-living species (i.e., unknown to establish symbiosis with any other marine host). Additionally, ephyrae did not display morphological variation or survivorship differences with varying symbionts. However, we observed intraspecific variation in time to induce strobilation with different cultured dinoflagellate strains.DiscussionThis work expands the known symbiont species that can form stable mutualisms with C. xamachana, primarily in the genera Symbiodinium and Breviolum. Additionally, we provide evidence of differences in ability of cultured symbiodiniaceans to establish symbiosis with a host, which suggests population-level differences in dinoflagellate cultures impact their symbiosis success. By utilizing an animal like C. xamachana with flexible symbiont uptake, we are able to explore how symbiont diversity can influence the timing and success of symbiosis-driven development.</p