Xenophagy of invasive bacteria is differentially activated and modulated via a TLR-TRAF6-Beclin1 axis in echinoderms.

In marine environments, organisms are confronted with numerous microbial challenges, although the differential regulation of xenophagy in response to different pathogenic bacterial species remains relatively unknown. Here, we addressed this issue using Apostichopus japonicus as a model. We identified 39 conserved autophagy-related genes by genome-wide screening, which provided a molecular basis for autophagy regulation in sea cucumbers. Furthermore, xenophagy of two Gram-negative bacteria, Vibrio splendidus and Escherichia coli, but not a Gram-positive bacteria, Micrococcus luteus, was observed in different autophagy assays. Surprisingly, a significantly higher autophagy capacity was found in the E. coli-challenged group than in the V. splendidus-challenged group. To confirm these findings, two different lipopolysaccharides, LPSV. splendidus and LPSE. coli, were isolated; we found that these LPS species differentially activated coelomocyte xenophagy. To explore the molecular mechanism mediating differential levels of xenophagy, we used an siRNA knockdown assay and confirmed that LPSV. splendidus-mediated xenophagy was dependent on an AjTLR3-mediated pathway, whereas LPSE. coli-mediated xenophagy was dependent on AjToll. Moreover, the activation of different AjTLRs resulted in AjTRAF6 ubiquitination and subsequent activation of K63-linked ubiquitination of AjBeclin1. Inversely, the LPSV. splendidus-induced AjTLR3 pathway simultaneously activated the expression of AjA20, which reduced the extent of K63-linked ubiquitination of AjBeclin1 and impaired the induction of autophagy; however, this finding was no t evident with LPSE. coli. Our present results provide the first evidence showing that xenophagy could be differentially induced by different bacterial species to yield differential autophagy levels in echinoderms.

Metagenomic sequencing suggests a diversity of RNA interference-like responses to viruses across multicellular eukaryotes.

RNA interference (RNAi)-related pathways target viruses and transposable element (TE) transcripts in plants, fungi, and ecdysozoans (nematodes and arthropods), giving protection against infection and transmission. In each case, this produces abundant TE and virus-derived 20-30nt small RNAs, which provide a characteristic signature of RNAi-mediated defence. The broad phylogenetic distribution of the Argonaute and Dicer-family genes that mediate these pathways suggests that defensive RNAi is ancient, and probably shared by most animal (metazoan) phyla. Indeed, while vertebrates had been thought an exception, it has recently been argued that mammals also possess an antiviral RNAi pathway, although its immunological relevance is currently uncertain and the viral small RNAs (viRNAs) are not easily detectable. Here we use a metagenomic approach to test for the presence of viRNAs in five species from divergent animal phyla (Porifera, Cnidaria, Echinodermata, Mollusca, and Annelida), and in a brown alga-which represents an independent origin of multicellularity from plants, fungi, and animals. We use metagenomic RNA sequencing to identify around 80 virus-like contigs in these lineages, and small RNA sequencing to identify viRNAs derived from those viruses. We identified 21U small RNAs derived from an RNA virus in the brown alga, reminiscent of plant and fungal viRNAs, despite the deep divergence between these lineages. However, contrary to our expectations, we were unable to identify canonical (i.e. Drosophila- or nematode-like) viRNAs in any of the animals, despite the widespread presence of abundant micro-RNAs, and somatic transposon-derived piwi-interacting RNAs. We did identify a distinctive group of small RNAs derived from RNA viruses in the mollusc. However, unlike ecdysozoan viRNAs, these had a piRNA-like length distribution but lacked key signatures of piRNA biogenesis. We also identified primary piRNAs derived from putatively endogenous copies of DNA viruses in the cnidarian and the echinoderm, and an endogenous RNA virus in the mollusc. The absence of canonical virus-derived small RNAs from our samples may suggest that the majority of animal phyla lack an antiviral RNAi response. Alternatively, these phyla could possess an antiviral RNAi response resembling that reported for vertebrates, with cryptic viRNAs not detectable through simple metagenomic sequencing of wild-type individuals. In either case, our findings show that the antiviral RNAi responses of arthropods and nematodes, which are highly divergent from each other and from that of plants and fungi, are also highly diverged from the most likely ancestral metazoan state.

New insights into the haemo- and coelo-microbiota with antimicrobial activities from Echinodermata and Mollusca.

AIMS: The aim of this study was to investigate the diversity of bacteria with antimicrobial activity present in the coelomic fluid and haemolymph of wild and healthy echinodermata and mollusca. METHODS AND RESULTS: Collection expeditions of healthy marine molluscs and echinoderms were conducted in the Glenan archipelago in spring 2014. Members of the culturable microbiota present in the haemolymph, (haemo-microbiota) of Haliotis tuberculata (gastropoda, abalone) and Mytilus edulis (bivalvia, mussel), as well as in the coelomic fluid (coelo-microbiota) of Echinus esculentus (echinoidea, sea urchin) and Holothuria forskali (Holothuroidea, holothurian) were screened for antimicrobial activity, and further identified using 16S rRNA sequencing. Except for E. esculentus, culturable bacteria in the internal fluids of all studied organisms (mussel, abalone and holothurian) were more abundant than in seawater. The haemo- and coelo-microbiota with antimicrobial activity differed significantly between host species, in terms of abundance and diversity. Indeed, higher numbers were isolated from mussel than from abalone haemolymph. Moreover, in mussels and holothurians, bacteria with antimicrobial activities were predominantly Vibrio spp. (respectively 55 and 45%), while Pseudoalteromonas spp. were the most abundant (50%) in abalone haemolymph. Nevertheless, the activity spectra of these bacteria mainly included marine pathogens affiliated to the Vibrio genus. CONCLUSION: The haemo- and coelo-microbiota with antimicrobial activities were significantly related to their host species and differed in terms of abundance and diversity. These bacteria may play a key role in host homeostasis against pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: This study brings new knowledge on the diversity of bacteria present in the internal fluids of two marine molluscs and two echinoderms and their antimicrobial activities towards marine pathogens.

Mono- and Dimeric Naphthalenones from the Marine-Derived Fungus Leptosphaerulina chartarum 3608.

Five new naphthalenones, two enantiomers (−)-1 and (+)-1 leptothalenone A, (−)-4,8-dihydroxy-7-(2-hydroxy-ethyl)-6-methoxy-3,4-dihydro-2H-naphthalen-1-one ((−)-2), (4S, 10R, 4’S)-leptotha-lenone B (5), (4R, 10S, 4’S)-leptothalenone B (6), and a new isocoumarine, 6-hydroxy-5,8-dimethoxy-3-methyl-1H-isochromen-1-one (4), along with two known compounds (+)-4,8-dihydroxy-7-(2-hydroxy-ethyl)-6-methoxy-3,4-dihydro-2H-naphthalen-1-one ((+)-2) and (+)-10-norparvulenone (3) were isolated from the marine-derived fungus Leptosphaerulina chartarum 3608. The structures of new compounds were elucidated by HR-ESIMS, NMR, and ECD analysis. All compounds were evaluated for cytotoxicity and anti-inflammatory activity. Compound 6 showed moderate anti-inflammatory activity by inhibiting the production of nitric oxide (NO) in lipopolysaccharide-stimulated RAW264.7 cells, with an IC50 value of 44.5 μM.

Epidemiology of a SKin Ulceration Disease (SKUD) in the sea cucumber Holothuria scabra with a review on the SKUDs in Holothuroidea (Echinodermata).

Aquacultivated sea cucumbers often suffer from SKin Ulceration Diseases (SKUDs). SKUDs have been observed in six holothuroid species from nine countries. All SKUDs present a similar symptom-the skin ulceration-and can be induced by bacteria, viruses, or abiotic factors. We here provide an update on SKUDs in holothuroids and analyse the case of the SKUD observed in Holothuria scabra in Madagascar. Field observations revealed a seasonality of the disease (i.e. wintertime maximum peak). Morphological analyses of integument ulcers showed that sea cucumbers react by forming a collagen fibre plug. Metagenomic analyses revealed a higher proportion of Vibrionaceae (Gammaproteobacteria) in ulcers in comparison to the healthy integument of the same individuals. Experimental infection assays were performed with ulcer crude extracts and bacteria isolated from these extracts (e.g. Vibrio parahaemolyticus) but did not significantly induce skin ulceration. Our results suggest that the disease is not induced by a pathogen or, at the very least, that the pathogen is not found within the ulcers as the disease is not transmissible by contact. An initial cause of the SKUD in Madagascar might be the repeated and prolonged exposures to cold temperatures. Opportunistic bacteria could settle in the dermis of ulcerated individuals and promote the ulcer extension. We propose a general nomenclature for SKUDs based on the acronym of the disease, the affected sea cucumber species (e.g. Hs for Holothuria scabra), the concerned region using an ISO code 3166-2 (e.g. MG for Madagascar), the description date (e.g. 20 for the year 2020), and, when known, the inducing agent (first letter of the general taxon, b for bacteria, v for virus in currently known cases; a a if it is an abiotic inducing parameter; nothing if the inducing cause has not been precisely identified). The disease described in this work will be designated under the name SKUD Hs-MG-20.

Fungal diversity and mycotoxin distribution in echinoderm aquaculture.

Aquaculture has been a growing sector of food production worldwide in the last decades, and now starts to include new, unconventional species from the Phylum Echinodermata, such as sea urchin (Paracentrotus lividus) and sea cucumber (Holothuria tubulosa). However, little is known in this context with regard to food safety aspects arising from toxigenic fungi. In this study, samples of feed (n = 7) and water (n = 8) or water filters (n = 4) from experimental aquaculture systems, producing sea urchin and sea cucumber, were analyzed by culture-based microbiological methods to assess fungal associations. Additionally, a search using molecular techniques for toxigenic sections within the genus Aspergillus in these materials was done. Finally, samples were analyzed for 37 mycotoxins by LC-MS/MS. In feed samples, Fusarium verticillioides and F. culmorum were detected. In water and water filter samples, Aureobasidium spp., Penicillium spp., and Cladosporium spp. were found. No genes of species from toxigenic Aspergillus sections were detected. Some feed samples were contaminated by multiple mycotoxins, namely deoxynivalenol (DON), zearalenone (ZEN), fumonisins (FBs), T-2 toxin, ochratoxin A (OTA), and mycophenolic acid (MPA). This is the first one study dealing with toxigenic fungi and mycotoxins in echinoderm-producting aquaculture. Although no clear evidence for adverse effects on the production systems could be found, the confirmed environmental association of mycotoxins and echinoderms requires further consideration. Studies on the consequences of introducing cereal-based fungi and their mycotoxins via feeds into aquaculture systems for echinoderm production seem to be advisable, to assess possible adverse effects on production and to clarify the potential impact on public health.

Cytocentrifugation as an additional method to study echinoderm coelomocytes: a comparative approach combining living cells, stained preparations, and energy-dispersive x-ray spectroscopy / Citocentrifugación como un método adicional para estudiar celomitos de equinodermos: un enfoque comparativo que combina células vivas, preparaciones teñidas y espectroscopía de rayos-x de dispersión de energía

Introduction: Echinoderm coelomocytes have traditionally been investigated through a morphological approach using light microscopy, which relies on the idea of constant cell shape as a stable character. However, this can be affected by biotic or abiotic conditions. Objective: To analyze if the consistency in cell morphology offered by the cytocentrifugation method, might be used as a convenient tool to study echinoderm coelomocytes. Methods: Cells of Echinaster (Othilia) brasiliensis (Asteroidea), Holothuria (Holothuria) tubulosa (Holothuroidea), Eucidaris tribuloides, Arbacia lixula, Lytechinus variegatus, and Echinometra lucunter (Echinoidea) were spread on microscope slides by cytocentrifugation, stained, and analyzed through light microscopy. Additionally, fluorescence microscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were applied to cytospin preparations, to complement the analysis of granular and colorless spherulocytes of Eucidaris tribuloides. Results: Altogether, 11 cell types, including phagocytes, spherulocytes, vibratile cells, and progenitor cells were identified in the samples analyzed. The granular spherulocyte, a newly-described cell type, was observed in all Echinoidea and was very similar to the acidophilic spherulocytes of Holothuria (Holothuria) tubulosa. Conclusions: Cytocentrifugation proved to be versatile, either as the main method of investigation in stained preparations, or as a framework on which other procedures may be performed. Its ability to maintain a constant morphology allowed accurate correspondence between live and fixed/stained cells, differentiation among similar spherulocytes as well as comparisons between similar cells of Holothuroidea and Echinoidea.

Introducción: Los celomocitos de equinodermos se han investigado tradicionalmente a través de un enfoque morfológico utilizando microscopía óptica, que se basa en la idea de la forma celular constante como un carácter estable. Sin embargo, esto puede verse afectado por condiciones bióticas o abióticas. Objetivo: Analizar si la consistencia en la morfología celular que ofrece el método de citocentrifugación podría utilizarse como una herramienta conveniente para estudiar los celomocitos de equinodermos. Métodos: Células de Echinaster (Othilia) brasiliensis (Asteroidea), Holothuria (Holothuria) tubulosa (Holothuroidea), Eucidaris tribuloides, Arbacia lixula, Lytechinus variegatus y Echinometra lucunter (Echinoidea) se esparcieron en portaobjetos de microscopio por citocentrifugación, se tiñeron y analizaron mediante microscopía óptica. Adicionalmente, se aplicó microscopía de fluorescencia, microscopía electrónica de barrido y espectroscopía de rayos X con dispersión de energía a las preparaciones de citoespina, para complementar el análisis de los esferulocitos granulares e incoloros de Eucidaris tribuloides. Resultados: En total, se identificaron en las muestras analizadas 11 tipos de células, incluidos fagocitos, esferulocitos, células vibrátiles y células progenitoras. El esferulocito granular, un tipo de célula recién descrito, se observó en todos los Echinoidea y fue muy similar a los esferulocitos acidófilos de Holothuria (Holothuria) tubulosa. Conclusiones: La citocentrifugación demostró ser un método bastante versátil, ya sea como el método principal de investigación en preparaciones teñidas o como un marco en el que se pueden realizar otros procedimientos. Su capacidad para mantener una morfología constante permitió una correspondencia precisa entre las células vivas y las células fijas/teñidas, la diferenciación entre esferulocitos similares, así como comparaciones entre células similares de Holothuroidea y Echinoidea.

Antimicrobial peptides in echinoderm host defense.

Antimicrobial peptides (AMPs) are important effector molecules in innate immunity. Here we briefly summarize characteristic traits of AMPs and their mechanisms of antimicrobial activity. Echinoderms live in a microbe-rich marine environment and are known to express a wide range of AMPs. We address two novel AMP families from coelomocytes of sea urchins: cysteine-rich AMPs (strongylocins) and heterodimeric AMPs (centrocins). These peptide families have conserved preprosequences, are present in both adults and pluteus stage larvae, have potent antimicrobial properties, and therefore appear to be important innate immune effectors. Strongylocins have a unique cysteine pattern compared to other cysteine-rich peptides, which suggests a novel AMP folding pattern. Centrocins and SdStrongylocin 2 contain brominated tryptophan residues in their native form. This review also includes AMPs isolated from other echinoderms, such as holothuroidins, fragments of beta-thymosin, and fragments of lectin (CEL-III). Echinoderm AMPs are crucial molecules for the understanding of echinoderm immunity, and their potent antimicrobial activity makes them potential precursors of novel drug leads.

[Yersinia pseudotuberculosis in a model marine ecosystem (experimental research)]. / Yersinia pseudotuberculosis v model'noi morskoi ékosisteme (éksperimental'noe issledovanie).

Materials on the behavior of Y. pseudotuberculosis in the model of marine ecosystem are presented. Y. pseudotuberculosis, both carrying and having lost the virulence plasmid of 45 MD, die in nonsterile sea water, but are capable of prolonged survival in sterile sea water and in the bodies of echinoderms. The death of these bacteria is accelerated in the presence of larvae of echinoderms. In sea water at low temperature Y. pseudotuberculosis maintained their high pathogenicity potential which they use on contact with eukaryotes. Under these conditions Y. pseudotuberculosis preserve their virulence plasmid, thus causing the disease and death of animals.

Echinoderms from Azores islands: an unexpected source of antibiotic resistant Enterococcus spp. and Escherichia coli isolates.

The prevalence of antibiotic resistance and the implicated mechanisms of resistance were evaluated in Enterococcus spp. and Escherichia coli, isolated from a total of 250 faecal samples of echinoderms collected from Azorean waters (Portugal). A total of 144 enterococci (120 Enterococcus faecium, 14 E. hirae, 8 E. faecalis, 2 E. gallinarum) and 10 E. coli were recovered. High percentages of resistance in enterococci were found for erythromycin, ampicillin, tetracyclin and ciprofloxacin. The erm(A) or erm(B), tet(M) and/or tet(L), vat(D), aac(6')-aph(2″) and aph(3')-IIIa genes were found in isolates resistant to erythromycin, tetracycline, quinupristin/dalfopristin, high-level gentamicin and high-level kanamycin, respectively. Resistance in E. coli isolates was detected for streptomycin, amikacin, tetracycline and tobramycin. The aadA gene was found in streptomycin-resistant isolates and tet(A)+tet(B) genes in tetracycline-resistant isolates. The data recovered are essential to improve knowledge about the dissemination of resistant strains through marine ecosystems and the possible implications involved in transferring these resistances either to other animals or to humans.

Sewage-exposed marine invertebrates: survival rates and microbiological accumulation.

A large number of bacteria, including agents responsible for diseases, characterise sewage-polluted seawaters. Apart from standards for bathing waters and bivalve aquaculture waters, there are no general microbiological standards applicable to seawaters to help decide if bacterial pollution is within acceptable ranges. This study represents an attempt towards the issue of comparing the susceptibility of different marine invertebrates subjected to polluted seawater with a high microbial contamination. We explored the survival rates and the microbiological accumulation of mollusc bivalves, echinoderms and crustaceans species exposed to sewage-polluted seawaters. Microbiological analyses were performed on the polluted seawater and on the homogenates of exposed and unexposed specimens. Culturable bacteria (22 °C and 37 °C) and microbial pollution indicators (total coliforms, Escherichia coli and intestinal enterococci) were measured. When exposed to the sewage-polluted seawater, the examined invertebrates showed different survival rates. In the filter feeders, bacterial densities at 22 °C and 37 °C rose after 96 h of exposure to sewage. The highest concentrations of total coliforms and intestinal enterococci were found in exposed bivalve Mytilus galloprovincialis. The concentrations of bacteria growing at 37 °C were lower in the exposed deposit feeders compared to the polluted seawater. Some yeasts were absent in several exposed species although these yeasts were present in the polluted seawater. Our data suggest that the examined filter feeders, given their capability to survive and accumulate bacteria, may counteract the effects of sewage and restore seawater quality.

The effects of chronic inorganic and organic phosphate exposure on bactericidal activity of the coelomic fluid of the sea urchin Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea).

The sea urchin Lytechinus variegatus can survive chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg L-1, and triethyl phosphate (organic phosphate) concentrations of 1000 mg L-1. However, chronic exposure to low (0.8 mg L-1 inorganic and 10 mg L-1 organic phosphate), medium (1.6 mg L-1 inorganic and 100 mg L-1 organic phosphate) or high (3.2 mg L-1 inorganic and 1000 mg L-1 organic phosphate) sublethal concentrations of these phosphates inhibit bactericidal clearance of the marine bacterium Vibrio sp. Bacteria were exposed to coelomic fluid collected from individuals maintained in either artificial seawater, or three concentrations of either inorganic phosphate or organic phosphate. Sterile marine broth, natural seawater and cell free coelomic fluid (cfCF) were employed as controls. Bacterial survival indices were measured at 0, 24 and 48 h periods once a week for four weeks. Bacteria were readily eliminated from the whole coelomic fluid (wCF) of individuals maintained in artificial seawater. Individuals maintained in inorganic phosphates were able to clear bacteria following a two week exposure period, while individuals maintained at even low concentrations of organic phosphates failed to clear all bacteria from their coelomic fluid. Exposure to phosphates represses antimicrobial defenses and may ultimately compromise survival of L. variegatus in the nearshore environment.

Pseudomonas marincola sp. nov., isolated from marine environments.

An aerobic, Gram-negative, motile, non-pigmented bacterium, strain KMM 3042(T), isolated from a deep-sea brittle star in the Fiji Sea, was subjected to a polyphasic taxonomic study. Phylogenetic analysis based on 16S rRNA gene sequences revealed marine Mn(II)-oxidizing isolate S185-2B as the closest neighbour of strain KMM 3042(T) (99.9 % sequence similarity). The two strains formed a distinct lineage within the genus Pseudomonas adjacent to the members of the Pseudomonas borbori cluster, sharing highest sequence similarity of 97.4 and 97.0 %, respectively, with P. borbori DSM 17834(T) and Pseudomonas flavescens DSM 12071(T). The DNA-DNA hybridization value (71 %) between strains KMM 3042(T) and S185-2B confirmed their assignment to the same species. On the basis of phylogenetic analysis, DNA-DNA hybridization and physiological and biochemical characterization, strains KMM 3042(T) and S185-2B should be assigned to a novel species of the genus Pseudomonas, for which the name Pseudomonas marincola sp. nov. is proposed. The type strain is KMM 3042(T) (=NRIC 0729(T) =JCM 14761(T)).

Marixanthomonas ophiurae gen. nov., sp. nov., a marine bacterium of the family Flavobacteriaceae isolated from a deep-sea brittle star.

An aerobic, Gram-negative, non-motile, yellow-pigmented bacterium, strain KMM 3046(T), was isolated from a deep-sea brittle star from the Fiji Sea and was subjected to a polyphasic taxonomic analysis. Strain KMM 3046(T) grew at 5-32 degrees C and in the presence of 1-12 % (w/v) NaCl. It contained MK-6 as the predominant menaquinone and 3-OH i16 : 0, 3-OH i17 : 0 and 3-OH a17 : 0 as the major fatty acids. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain KMM 3046(T) forms a distinct evolutionary lineage within the family Flavobacteriaceae (phylum Bacteroidetes), displaying 92.3-91.9 % sequence similarity with respect to Salegentibacter species. On the basis of the phenotypic and phylogenetic data, strain KMM 3046(T) represents a novel genus and species of the family Flavobacteriaceae, for which the name Marixanthomonas ophiurae gen. nov., sp. nov. is proposed. The type strain of Marixanthomonas ophiurae is KMM 3046(T) (=NRIC 0684(T)=JCM 14121(T)).

Subcuticular bacteria from the brittle star Ophiactis balli (Echinodermata: Ophiuroidea) represent a new lineage of extracellular marine symbionts in the alpha subdivision of the class Proteobacteria.

Many species of echinoderms, in all five extant classes, contain subcuticular bacterial symbionts (SCB). The role of these extracellular symbionts and the nature of the relationship remain unclear. We have sequenced 16S rRNA genes from symbionts to determine their phylogenetic affinities. Symbionts of an ophiuroid, Ophiactis balli, appear closely related to bacteria within the alpha group of the class Proteobacteria, including intracellular endosymbionts and pathogens. SCB are clearly of separate origin from other documented major groups of marine symbiotic bacteria.

Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples.

Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3,600-m depth) and southeast (4,300- and 5200-m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67 to 0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3 to 5 degrees C and 360, 430, or 520 atmospheres) were relatively slow, ranging from 0.09 to 0.39 nmol g-1 day-1, whereas rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. From the results of this study, it was concluded that microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure. Furthermore, rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments.