Photoprotection-related properties of a raw extract from Gordonia hongkongensis EUFUS-Z928: A culturable rare actinomycete associated with the Caribbean octocoral Eunicea fusca.

UV filters in current sunscreen formulations can have negative effects on human health, such as endocrine disruption and allergic reactions, as well as on the environment, including bioaccumulation and coral health toxicity. As a result, there is a need to find alternative compounds that serve as safer and more ecofriendly active ingredients. This study successfully isolated actinomycetes from the octocoral Eunicea fusca and assessed their potential as producers of photoprotective compounds. The use of bio-based chemical agents, particularly natural products, has been a highly effective strategy for discovering bioactive compounds, especially in marine invertebrates and their associated microbiota. Eighteen bacterial isolates were obtained and subsequently employed to prepare raw methanolic extracts from seven-day submerged cultures in Zobell marine broth. The resulting extracts were screened for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity and characterized by total phenolic and flavonoid content measurements. After screening, the Gordonia hongkongensis EUFUS-Z928-derived raw extract exhibited the best antioxidant profile, i.e. DPPH and ABTS radical scavenging of 4.93 and 6.00 µmol Trolox per gram of extract, respectively, and selected for further photoprotection-related analysis. Thus, this extract demonstrated a UV-absorbing capacity of 46.33% of the in vitro sun protection factor calculated for 30 µg/mL oxybenzone but did not exhibit any cytotoxicity on human dermal fibroblasts (HDFa cell line) at concentrations up to 500 µg/mL. The liquid chromatography-mass spectrometry chemical characterization of this extract showed compounds with structural features associated with free radical scavenging and UV absorption (i.e. photoprotection-related activities). These findings highlighted the potential of the microbiota associated with E. fusca and confirmed the feasibility of exploiting its metabolites for photoprotection-related purposes.

Measuring multi-year changes in the Symbiodiniaceae algae in Caribbean corals on coral-depleted reefs.

Monitoring coral cover can describe the ecology of reef degradation, but rarely can it reveal the proximal mechanisms of change, or achieve its full potential in informing conservation actions. Describing temporal variation in Symbiodiniaceae within corals can help address these limitations, but this is rarely a research priority. Here, we augmented an ecological time series of the coral reefs of St. John, US Virgin Islands, by describing the genetic complement of symbiotic algae in common corals. Seventy-five corals from nine species were marked and sampled in 2017. Of these colonies, 41% were sampled in 2018, and 72% in 2019; 28% could not be found and were assumed to have died. Symbiodiniaceae ITS2 sequencing identified 525 distinct sequences (comprising 42 ITS2 type profiles), and symbiont diversity differed among host species and individuals, but was in most cases preserved within hosts over 3 yrs that were marked by physical disturbances from major hurricanes (2017) and the regional onset of stony coral tissue loss disease (2019). While changes in symbiont communities were slight and stochastic over time within colonies, variation in the dominant symbionts among colonies was observed for all host species. Together, these results indicate that declining host abundances could lead to the loss of rare algal lineages that are found in a low proportion of few coral colonies left on many reefs, especially if coral declines are symbiont-specific. These findings highlight the importance of identifying Symbiodiniaceae as part of a time series of coral communities to support holistic conservation planning. Repeated sampling of tagged corals is unlikely to be viable for this purpose, because many Caribbean corals are dying before they can be sampled multiple times. Instead, random sampling of large numbers of corals may be more effective in capturing the diversity and temporal dynamics of Symbiodiniaceae metacommunities in reef corals.

Microbiota of healthy and bleached corals of the species Siderastrea stellata in response to river influx and seasonality in Brazilian northeast.

Although coral bleaching is increasing worldwide due to warming oceans exacerbated by climate change, there has been a growing recognition that local stressors may play an additional role. Important stressors include the physicochemical and microbiological influences that are related to river runoff. Here, we investigated the microbiota associated to mucus and tissue of endemic coral Siderastrea stellata, collected from Brazilian northeast coral reefs of Barra de Santo Antônio (subject to river runoff) and Maragogi (minimal river runoff) during both the rainy and dry seasons. We sequenced the V4 region of 16S rDNA and used multiple R packages to process raw data and performed statistical analysis to reveal the microbial community structure composition and functional predictions. Major dissimilarities between microbial communities were related to seasonality, while healthy and bleached specimens were mainly associated with the enrichment of several less abundant taxa involved in specific metabolic functions, mainly related to the nitrogen cycle. We were not able to observe the dominance of groups that has been previously associated with bleachings, such as Vibrionaceae or Burkholderiaceae. The influx of freshwater appears to increase the homogeneity between individuals in Barra de Santo Antonio, especially during the rainy season. By contrast, we observed an increased homogeneity between samples in Maragogi during the dry season. Understanding the dynamics of the coral microbiota and how bleaching appears in response to specific environmental variables, in addition to determining the conditions that lead to a more robust coral microbiota, is essential for choosing the most appropriate area and conservation methods, for example.

Computational peptidology approach to the study of the chemical reactivity and bioactivity properties of Aspergillipeptide D, a cyclopentapeptide of marine origin.

Aspergillipeptide D is a cyclic pentapeptide isolated from the marine gorgonian Melitodes squamata-derived fungus Aspergillus sp. SCSIO 41501 that it has been shown to present moderate activity against herpes virus simplex type 1 (HSV-1). Thus, this paper presents the results of a computational study of this cyclopentapeptide's chemical reactivity and bioactivity properties using a CDFT-based computational peptidology (CDFT-CP) methodology, which is derived from combining chemical reactivity descriptors derived from Conceptual Density Functional Theory (CDFT) and some Cheminformatics tools which may be used. This results in an improvement of the virtual screening procedure by a similarity search allowing the identification and validation of the known ability of the peptide to act as a possible useful drug. This was followed by an examination of the drug's bioactivity and pharmacokinetics indices in relation to the ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) characteristics. The findings provide further evidence of the MN12SX density functional's superiority in proving the Janak and Ionization Energy theorems using the proposed KID approach. This has proven to be beneficial in accurately predicting CDFT reactivity characteristics, which aid in the understanding of chemical reactivity. The Computational Pharmacokinetics study revealed the potential ability of Aspergillipeptide D as a therapeutic drug through the interaction with different target receptors. The ADMET indices confirm this assertion through the absence of toxicity and good absorption and distribution properties.

CPR and DPANN Have an Overlooked Role in Corals' Microbial Community Structure.

Understanding how microbial communities are structured in coral holobionts is important to estimate local and global impacts and provide efficient environment management strategies. Several studies investigated the relationship between corals and their microbial communities, including the environmental drivers of shifts in this relationship, associated with diseases and coral cover loss. However, these studies are often geographically or taxonomically restricted and usually focused on the most abundant microbial groups, neglecting the rare biosphere, including archaea in the group DPANN and the recently discovered bacterial members of the candidate phyla radiation (CPR). Although it is known that rare microbes can play essential roles in several environments, we still lack understanding about which taxa comprise the rare biosphere of corals' microbiome. Here, we investigated the host-related and technical factors influencing coral microbial community structure and the importance of CPR and DPANN in this context by analyzing more than a hundred coral metagenomes from independent studies worldwide. We show that coral genera are the main biotic factor shaping coral microbial communities. We also detected several CPR and DPANN phyla comprising corals' rare biosphere for the first time and showed that they significantly contribute to shaping coral microbial communities.

Antimicrobial activity of bacteria isolated from tissue of the coral Palythoa caribaeorum (Zoantharia: Sphenopidae) from Paraíba, Brazil coastal reefs / Actividad antimicrobiana de bacterias aisladas del tejido del coral Palythoa caribaeorum (Zoantharia: Sphenopidae) de los arrecifes costeros de Paraíba, Brasil

Abstract Introduction: The coral-associated bacteria with antimicrobial activity may be important to promote the health of their host through various interactions, and may be explored as a source of new bioactive compounds. Objective: To analyze the antimicrobial activity of bacteria associated with the zoanthid Palythoa caribaeorum from the coral reefs of Carapibus, Paraiba state, Brazil. Methods: The phylogenetic analysis of the bacteria was conducted based on partial sequences of the 16S rRNA gene using molecular and bioinformatics tools. The antimicrobial activity of the 49 isolates was tested against four bacterial strains and one yeast strain: Bacillus cereus (CCT0198), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa and Candida albicans (ATCC 10231). The antibiosis and antibiogram assays were conducted and the Minimal Inhibitory Concentration (MIC) was determined by the microdilution method. Results: The bacterial isolates belonged to Firmicutes phylum (84 % of the isolates) and the Proteobacteria phylum (16 % of the isolates). Among the 49 isolates five genera were found, with the Bacillus genus being the most abundant (82 % of the isolates), followed by Vibrio (10 %), Pseudomonas (4 %), Staphylococcus (2 %) and Alteromonas (2 %). Antibiosis test revealed that 16 isolates (33 %) showed antimicrobial activity against one or more of five tested reference strains. The highest number of antagonistic bacteria were found in the Bacillus genus (12 isolates), followed by Vibrio (three isolates) and Pseudomonas (one isolate) genera. The B. subtilis NC8 was the only isolate that inhibited all tested strains in the antibiosis assay. However, antibiogram test with post-culture cell-free supernatant of NC8 isolate showed the inhibition of only B. cereus, S. aureus and C. albicans, and the lyophilized and dialyzed material of this isolate inhibited only B. cereus. The lyophilized material showed bacteriostatic activity against B. cereus, with a MIC value of 125 μg/μl, and in the cytotoxicity assay, the hemolysis value was of 4.8 %, indicating its low cytotoxicity. Conclusions: The results show the antimicrobial potential of some bacterial isolates associated with the P. caribaeourum tissue, especially those belonged to Bacillus genus.

Resumen Introducción: La actividad antimicrobiana realizada por las bacterias asociadas con los corales, además de promover la salud de su huésped, representa una fuente para obtener nuevos compuestos bioactivos. Objetivo: Analizar la actividad antimicrobiana de las bacterias asociadas con el zoantario Palythoa caribaeorum de los arrecifes de Carapibus, Paraíba, Brasil. Metodología: El análisis filogenético de la bacterias se realizó con base en secuencias parciales del gen RNAr 16S utilizando herramientas moleculares y de bioinformática. La actividad antimicrobiana de las cepas se probó contra cuatro cepas bacterianas y una cepa de levadura: Bacillus cereus (CCT0198), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa y Candida albicans (ATCC 10231), utilizando ensayos antibiosis y antibiograma, y la concentración inhibitoria mínima (CIM) que se determinó por el método de microdilución. Resultados: Las cepas bacterianas pertenecían a Firmicutes (84 %) y Gammaproteobacteria (16 %). Entre 49 cepas se encontraron cinco géneros de bacterias: Bacillus, Vibrio, Pseudomonas, Staphylococcus y Alteromonas. Un total de 19 cepas exhibieron actividad antimicrobiana, siendo el género Bacillus el responsable del mayor número de bacterias antagonistas, con 12 cepas positivas en el ensayo de antibiosis y cuatro en la prueba de antibiograma. El mayor número de bacterias antagonistas se encontró en Bacillus (12 aislamientos), seguido por Vibrio (tres aislamientos) y Pseudomonas (un aisladmiento). El NC8, clasificado como Bacillus subtilis, inhibió todas las cepas estándar en el ensayo de antibiosis y las cepas de B. cereus, S. aureus y C. albicans en la prueba de antibiograma. El material liofilizado del B. subtilis NC8 mostró acción bacteriostática contra B. cereus, con un valor de CIM de 125 μg/μl. En la prueba de citotoxicidad, el grado de hemólisis fue del 4.8 % para el material liofilizado a las concentraciones probadas, lo que indica su baja citotoxicidad. Conclusión: Los resultados muestran el potencial antimicrobiano de algunos aislamientos bacterianos asociados al P. caribaeourum, especialmente los pertenecientes al género Bacillus.

Semisynthesis, Antiplasmodial Activity, and Mechanism of Action Studies of Isocoumarin Derivatives.

In this study, eight natural isocoumarins (1-8) were isolated from a marine-derived Exserohilum sp. fungus. To explore their structure-activity relationship and discover potent antimalarial leads, a small library of 22 new derivatives (1a-1n, 2a, 3a-3c, 4a-4c, and 7a) were semisynthesized by varying the substituents of the aromatic ring and the aliphatic side chains. The natural compound (1) and three semisynthetic derivatives (1d, 1n, and 2a), possessing an all-cis stereochemistry, exhibited strong antiplasmodial activity with IC50 values of 1.1, 0.8, 0.4, and 2.6 µM, respectively. Mechanism studies show that 1n inhibits hemozoin polymerization and decreases the mitochondrial membrane potential but also inhibits P. falciparum DNA gyrase. 1n not only combines different mechanisms of action but also exhibits a high therapeutic index (CC50/IC50 = 675), high selectivity, and a notable drug-like profile.

The microbial profile of a tissue necrosis affecting the Atlantic invasive coral Tubastraea tagusensis.

The Southwestern Atlantic rocky reef ecosystems are undergoing significant changes due to sun-corals (Tubastraea tagusensis and T. coccinea) invasion. At Búzios Island, on the northern coast of São Paulo State, where the abundance of T. tagusensis is particularly high, some colonies are displaying tissue necrosis, a phenomenon never reported for this invasive nor any other azooxanthellate coral species. Using next-generation sequencing, we sought to understand the relationship between T. tagusensis tissue necrosis and its microbiota. Thus, through amplicon sequencing, we studied both healthy and diseased coral colonies. Results indicate a wide variety of bacteria associated with healthy colonies and an even higher diversity associated with those corals presenting tissue necrosis, which displayed nearly 25% more microorganisms. Also, as the microbial community associated with the seven healthy colonies did not alter composition significantly, it was possible to verify the microbial succession during different stages of tissue necrosis (i.e., initial, intermediate, and advanced). Comparing the microbiome from healthy corals to those in early tissue necrosis suggests 21 potential pathogens, which might act as the promoters of such disease.

Genome sequence of Vibrio fluvialis 362.3 isolated from coral Mussismilia braziliensis reveals genes related to marine environment adaptation.

Vibrio fluvialis is a halophilic bacterium frequently found in estuarine and coastal waters environments. The strain 362.3 was isolated from Mussismilia braziliensis coral of Abrolhos Bank. In this study, to gain insights into the marine adaptation in V. fluvialis, we sequenced the genome of 362.3 strain, which comprised 4,607,294 bp with a G + C content of 50.2%. In silico analysis showed that V. fluvialis 362.2 encodes genes related to chitin catabolic pathway, iron metabolism, osmotic stress and membrane transport.

Insights into the genomic repertoire of Aquimarina litoralis CCMR20, a symbiont of coral Mussismilia braziliensis.

Aquimarina litoralis CCMR20 originated from the coral Mussismilia braziliensis (Sebastião Gomes Reef, Brazil, summer 2010). To gain new insights into the genomic repertoire associated with symbioses, we obtained the genome sequence of this strains using Illumina sequencing. CCMR20 has a genome size of 6.3 Mb, 32.6%GC, and 5513 genes (37 tRNA and 4 rRNA). A more fine-grained examination of the gene repertoire of CCMR20 disclosed genes engaged with symbiosis (heterotrophic carbon metabolism, CAZymes, B-vitamins group, carotenoid pigment and antioxidant molecules production). Genomic evidence further expand the possible relevance of this symbiont in the health of Mussismilia holobiont.Whole Genome Shotgun project has been deposited at DDBJ/ENA/GeneBank under the accession number WEKL00000000.

Conserved Pigment Profiles in Phylogenetically Diverse Symbiotic Bacteria Associated with the Corals Montastraea cavernosa and Mussismilia braziliensis.

Pigmented bacterial symbionts play major roles in the health of coral holobionts. However, there is scarce knowledge on the diversity of these microbes for several coral species. To gain further insights into holobiont health, pigmented bacterial isolates of Fabibacter pacificus (Bacteroidetes; n = 4), Paracoccus marcusii (Alphaproteobacteria; n = 1), and Pseudoalteromonas shioyasakiensis (Gammaproteobacteria; n = 1) were obtained from the corals Mussismilia braziliensis and Montastraea cavernosa in Abrolhos Bank, Brazil. Cultures of these bacterial symbionts produced strong antioxidant activity (catalase, peroxidase, and oxidase). To explore these bacterial isolates further, we identified their major pigments by HPLC and mass spectrometry. The six phylogenetically diverse symbionts had similar pigment patterns and produced myxol and keto-carotene. In addition, similar carotenoid gene clusters were confirmed in the whole genome sequences of these symbionts, which reinforce their antioxidant potential. This study highlights the possible roles of bacterial symbionts in Montastraea and Mussismilia holobionts.

Genome Mining, Microbial Interactions, and Molecular Networking Reveals New Dibromoalterochromides from Strains of Pseudoalteromonas of Coiba National Park-Panama.

The marine bacterial genus Pseudoalteromonas is known for their ability to produce antimicrobial compounds. The metabolite-producing capacity of Pseudoalteromonas has been associated with strain pigmentation; however, the genomic basis of their antimicrobial capacity remains to be explained. In this study, we sequenced the whole genome of six Pseudoalteromonas strains (three pigmented and three non-pigmented), with the purpose of identifying biosynthetic gene clusters (BGCs) associated to compounds we detected via microbial interactions along through MS-based molecular networking. The genomes were assembled and annotated using the SPAdes and RAST pipelines and mined for the identification of gene clusters involved in secondary metabolism using the antiSMASH database. Nineteen BGCs were detected for each non-pigmented strain, while more than thirty BGCs were found for two of the pigmented strains. Among these, the groups of genes of nonribosomal peptide synthetases (NRPS) that code for bromoalterochromides stand out the most. Our results show that all strains possess BGCs for the production of secondary metabolites, and a considerable number of distinct polyketide synthases (PKS) and NRPS clusters are present in pigmented strains. Furthermore, the molecular networking analyses revealed two new molecules produced during microbial interactions: the dibromoalterochromides D/D' (11-12).

Ecological and biotechnological importance of secondary metabolites produced by coral-associated bacteria.

Symbiotic relationships between corals and their associated micro-organisms are essential to maintain host homeostasis. Coral-associated bacteria (CAB) can have different beneficial roles in the coral metaorganism, such as metabolizing essential nutrients for the coral host and protecting the coral from pathogens. Many CAB exert these functions via secondary metabolites, which include antibacterial, antifouling, antitumour, antiparasitic and antiviral compounds. This review describes how analysis of CAB has led to the discovery of secondary metabolites with potential biotechnological applications. The most commonly found types of secondary metabolites, antimicrobial and antibiofilm compounds, are emphasized and described. Recently developed methods that can be applied to enhance the culturing of CAB from shallow-water reefs and the less-studied deep-sea coral reefs are also discussed. Last, we suggest how the combined use of meta-omics and innovative growth-diffusion techniques can vastly improve the discovery of novel compounds in coral environments.

Patterns of environmental variability influence coral-associated bacterial and algal communities on the Mesoamerican Barrier Reef.

A coral's capacity to alter its microbial symbionts may enhance its fitness in the face of climate change. Recent work predicts exposure to high environmental variability may increase coral resilience and adaptability to future climate conditions. However, how this heightened environmental variability impacts coral-associated microbial communities remains largely unexplored. Here, we examined the bacterial and algal symbionts associated with two coral species of the genus Siderastrea with distinct life history strategies from three reef sites on the Belize Mesoamerican Barrier Reef System with low or high environmental variability. Our results reveal bacterial community structure, as well as alpha- and beta-diversity patterns, vary by host species. Differences in bacterial communities between host species were partially explained by high abundance of Deltaproteobacteria and Rhodospirillales and high bacterial diversity in Siderastrea radians. Our findings also suggest Siderastrea spp. have dynamic core bacterial communities that likely drive differences observed in the entire bacterial community, which may play a critical role in rapid acclimatization to environmental change. Unlike the bacterial community, Symbiodiniaceae composition was only distinct between host species at high thermal variability sites, suggesting that different factors shape bacterial versus algal communities within the coral holobiont. Our findings shed light on how domain-specific shifts in dynamic microbiomes may allow for unique methods of enhanced host fitness.

Diel, daily, and spatial variation of coral reef seawater microbial communities.

Reef organisms influence microorganisms within the surrounding seawater, yet the spatial and temporal dynamics of seawater microbial communities located in proximity to corals are rarely investigated. To better understand reef seawater microbial community dynamics over time and space, we collected small-volume seawater samples during the day and night over a 72 hour period from three locations that differed in spatial distance from 5 Porites astreoides coral colonies on a shallow reef in St. John, U.S. Virgin Islands: near-coral (sampled 5 cm horizontally from each colony), reef-depth (sampled 2 m above each colony) and surface seawater (sampled 1 m from the seawater surface). At all time points and locations, we quantified abundances of microbial cells, sequenced small subunit rRNA genes of bacterial and archaeal communities, and measured inorganic nutrient concentrations. Prochlorococcus and Synechococcus cells were consistently elevated at night compared to day and these abundances changed over time, corresponding with temperature, nitrite, and silicate concentrations. During the day, bacterial and archaeal alpha diversity was significantly higher in reef-depth and near-coral seawater compared to the surface seawater, signifying that the reef influences the diversity of the seawater microorganisms. At night, alpha diversity decreased across all samples, suggesting that photosynthesis may favor a more taxonomically diverse community. While Prochlorococcus exhibited consistent temporal rhythmicity, additional taxa were enriched in reef seawater at night compared to day or in reef-depth compared to surface seawater based on their normalized sequence counts. There were some significant differences in nutrient concentrations and cell abundances between reef-depth and near-coral seawater but no clear trends. This study demonstrates that temporal variation supersedes small-scale spatial variation in proximity to corals in reef seawater microbial communities. As coral reefs continue to change in benthic composition worldwide, monitoring microbial composition in response to temporal changes and environmental fluctuations will help discern normal variability from longer lasting changes attributed to anthropogenic stressors and global climate change.

Microbial signatures of protected and impacted Northern Caribbean reefs: changes from Cuba to the Florida Keys.

There are a few baseline reef-systems available for understanding the microbiology of healthy coral reefs and their surrounding seawater. Here, we examined the seawater microbial ecology of 25 Northern Caribbean reefs varying in human impact and protection in Cuba and the Florida Keys, USA, by measuring nutrient concentrations, microbial abundances, and respiration rates as well as sequencing bacterial and archaeal amplicons and community functional genes. Overall, seawater microbial composition and biogeochemistry were influenced by reef location and hydrogeography. Seawater from the highly protected 'crown jewel' offshore reefs in Jardines de la Reina, Cuba had low concentrations of nutrients and organic carbon, abundant Prochlorococcus, and high microbial community alpha diversity. Seawater from the less protected system of Los Canarreos, Cuba had elevated microbial community beta-diversity whereas waters from the most impacted nearshore reefs in the Florida Keys contained high organic carbon and nitrogen concentrations and potential microbial functions characteristic of microbialized reefs. Each reef system had distinct microbial signatures and within this context, we propose that the protection and offshore nature of Jardines de la Reina may preserve the oligotrophic paradigm and the metabolic dependence of the community on primary production by picocyanobacteria.

Diversity of filamentous fungi associated with coral and sponges in coastal reefs of northeast Brazil.

Fungi are known to form associations with various marine organisms and substrata such as sponges and corals, both as potential symbionts or pathogens. These microorganisms occupy an ecological niche that has recently attracted great attention due to their potential in either ecological or pharmaceutical advances. However, the interaction between marine invertebrates and fungi is still poorly understood, including how they are affected by anthropogenic actions. Here, we identified 89 fungal isolates through sequencing of the ITS rDNA region obtained from the various sponge and coral species collected at two northeast Brazilian reefs. We found 43 species of fungi from 16 genera, all belonging to phylum Ascomycota. The sponges and coral shared four genera: Aspergillus, Penicillium, Trichoderma, and Cladosporium, all commonly found in terrestrial habitats and associated with marine invertebrates. We observed some unusual species in relation to the marine environment, such as Clonostachys rosea and Neopestalotiopsis clavispora, most of them related to plants, either as saprophytic or pathogenic, suggesting that these species were transported from the surrounding terrestrial environment to the reefs. In addition, some isolates represent possible undescribed species, reinforcing the importance of studying the marine environment in relation to its ecological and biotechnological importance.

Metagenome of Acropora palmata coral rubble: Potential metabolic pathways and diversity in the reef ecosystem.

Over the past 30 years, the stony coral Acropora palmata has experienced an excessive loss of individuals showing few signs of recovery throughout the Mexican Caribbean, resulting in long stretches of coral rubble structures. When the coral dies, the skeleton begins to be colonized by algae, sponges, virus, bacteria and other microorganisms, forming a new community. Here we analyze, using a metagenomic approach, the diversity and biogeochemical cycles associated to coral rubble in La Bocana (Puerto Morelos, QRoo, Mexico). This study provides the first broad characterization of coral rubble associated communities and their role in biogeochemical cycling, suggesting a potential view of a world where coral reefs are no longer dominated by corals.

Acidification-induced cellular changes in Symbiodinium isolated from Mussismilia braziliensis.

Dinoflagellates from the Symbiodiniaceae family and corals have an ecologically important endosymbiotic relationship. Scleractinian corals cannot survive for long periods without their symbionts. These algae, also known as zooxanthellae, on the other hand, thrives outside the coral cells. The free-living populations of zooxanthellae are essential for the resilience of the coral to environmental stressors such as temperature anomalies and ocean acidification. Yet, little is known about how ocean acidification may affect the free-living zooxanthellae. In this study we aimed to test morphological, physiological and biochemical responses of zooxanthellae from the Symbiodinium genus isolated from the coral Mussismilia braziliensis, endemic to the Brazilian coast, to acidification led by increased atmospheric CO2. We tested whether photosynthetic yield, cell ultrastructure, cell density and lipid profile would change after up to 16 days of exposure to pH 7.5 in an atmospheric pCO2 of 1633 µatm. Photosynthetic yield and cell density were negatively affected and chloroplasts showed vesiculated thylakoids, indicating morphological damage. Moreover, Symbiodinium fatty acid profile drastically changed in acidified condition, showing lower polyunsaturated fatty acids and higher saturated fatty acids contents, when compared to the control, non-acidified condition. These results show that seawater acidification as an only stressor causes significant changes in the physiology, biochemistry and ultrastructure of free-living Symbiodinium.

Halomonas coralii sp. nov. Isolated from Mussismilia braziliensis.

We report here the novel species Halomonas coralii. The nearly complete genome of strain 362.1T consisted of 4.4 Mbp (3989 CDS; 66.3% GC). Genomic taxonomy analysis demonstrates that the novel strain has < 83% AAI and < 29% GGDH towards its closest neighbors.