Developing an effective marine eDNA monitoring: eDNA detection at pre-outbreak densities of corallivorous seastar (Acanthaster cf. solaris).

Outbreaks of the corallivorous Crown-of-Thorns Seastar (CoTS) Acanthaster cf. solaris contribute significantly to coral reef loss. Control of outbreaks is hampered because standard monitoring techniques do not detect outbreaks at early (low density) stages, thus preventing early intervention. We previously demonstrated that eDNA monitoring can detect CoTS at intermediate densities. Here, we test whether detection probability can be improved by (i) targeted site selection or collection at specific times and (ii) moving from an average eDNA copy number approach (based on the limit of quantification) to a presence/absence approach (based on the limit of detection). Using a dataset collected over three years and multiple reef sites, we demonstrated that adding water residence age, sea surface level and temperature into generalized linear models explained low amounts of variance of eDNA copy numbers. Site specific CoTS density, by contrast, was a significant predictor for eDNA copy numbers. Bayesian multi-scale occupancy modelling of the presence/absence data demonstrated that the probability of sample capture (θ) on most reefs with intermediate or high CoTS densities was >0.8. Thus, confirming CoTS presence on these reefs would only require 2-3 samples. Sample capture decreased with decreasing CoTS density. Collecting ten filters was sufficient to reliably (based on the lower 95 % Credibility Interval) detect CoTS below nominal outbreak levels (3 Ind. ha-1). Copy number-based estimates may be more relevant to quantify CoTS at higher densities. Although water residence age did contribute little to our models, sites with higher residence times may serve as sentinel sites accumulating eDNA. The approach based on presence or absence of eDNA facilitates eDNA monitoring to detect CoTS densities below outbreak thresholds and we continue to further develop this method for quantification.

Knowledge Gaps in the Biology, Ecology, and Management of the Pacific Crown-of-Thorns Sea Star Acanthaster sp. on Australia's Great Barrier Reef.

AbstractCrown-of-thorns sea stars (Acanthaster sp.) are among the most studied coral reef organisms, owing to their propensity to undergo major population irruptions, which contribute to significant coral loss and reef degradation throughout the Indo-Pacific. However, there are still important knowledge gaps pertaining to the biology, ecology, and management of Acanthaster sp. Renewed efforts to advance understanding and management of Pacific crown-of-thorns sea stars (Acanthaster sp.) on Australia's Great Barrier Reef require explicit consideration of relevant and tractable knowledge gaps. Drawing on established horizon scanning methodologies, this study identified contemporary knowledge gaps by asking active and/or established crown-of-thorns sea star researchers to pose critical research questions that they believe should be addressed to improve the understanding and management of crown-of-thorns sea stars on the Great Barrier Reef. A total of 38 participants proposed 246 independent research questions, organized into 7 themes: feeding ecology, demography, distribution and abundance, predation, settlement, management, and environmental change. Questions were further assigned to 48 specific topics nested within the 7 themes. During this process, redundant questions were removed, which reduced the total number of distinct research questions to 172. Research questions posed were mostly related to themes of demography (46 questions) and management (48 questions). The dominant topics, meanwhile, were the incidence of population irruptions (16 questions), feeding ecology of larval sea stars (15 questions), effects of elevated water temperature on crown-of-thorns sea stars (13 questions), and predation on juveniles (12 questions). While the breadth of questions suggests that there is considerable research needed to improve understanding and management of crown-of-thorns sea stars on the Great Barrier Reef, the predominance of certain themes and topics suggests a major focus for new research while also providing a roadmap to guide future research efforts.

DNA-Based Detection and Patterns of Larval Settlement of the Corallivorous Crown-of-Thorns Sea Star (Acanthaster sp.).

AbstractPopulation irruptions of the western Pacific crown-of-thorns sea star (Acanthaster sp.) are a perennial threat to coral reefs and may be initiated by fluctuations in reproductive or settlement success. However, the processes dictating their early life history, particularly larval settlement, remain poorly understood given limitations in sampling larvae and newly settled juveniles in the field. Here, we introduce an innovative method to measure crown-of-thorns sea star settlement, using artificial settlement collectors and droplet digital polymerase chain reaction based on crown-of-thorns sea star-specific mitochondrial DNA primers. This study demonstrated the utility of this method and explored temporal and spatial patterns of crown-of-thorns sea star settlement on the Great Barrier Reef from 2016 to 2020. Settlement varied considerably between sampling periods at Rib Reef and peaked between October 2016 and January 2017. Our results further suggest that crown-of-thorns sea star larvae readily settle in shallow reef environments, with no preferential settlement detected between depths tested (4-12 m). Substantial variation between Great Barrier Reef regions was revealed in 2019-2020, because collectors deployed on reefs in the central Great Barrier Reef were >10 times as likely to record newly settled crown-of-thorns sea stars as reefs in the northern Great Barrier Reef near Lizard Island. The trends reported here add to our understanding of this critical life-history stage; however, further method validation and larger-scale studies are needed to address pertinent information gaps, such as the stock-recruitment dynamics of this species. Most importantly, fluctuations in crown-of-thorns sea star settlement can now be detected using this sampling protocol, which demonstrates its utility in heralding new and renewed population irruptions of this destructive sea star.

Author Correction: DNA-based identification of predators of the corallivorous Crown-of-Thorns Starfish (Acanthaster cf. solaris) from fish faeces and gut contents.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

DNA-based identification of predators of the corallivorous Crown-of-Thorns Starfish (Acanthaster cf. solaris) from fish faeces and gut contents.

The corallivorous Crown-of-Thorns Starfish (CoTS, Acanthaster spp.) has been linked with the widespread loss of scleractinian coral cover on Indo-Pacific reefs during periodic population outbreaks. Here, we re-examine CoTS consumption by coral reef fish species by using new DNA technologies to detect Pacific Crown-of-Thorns Starfish (Acanthaster cf. solaris) in fish faecal and gut content samples. CoTS DNA was detected in samples from 18 different coral reef fish species collected on reefs at various stages of CoTS outbreaks in the Great Barrier Reef Marine Park, nine of which had not been previously reported to feed on CoTS. A comprehensive set of negative and positive control samples confirmed that our collection, processing and analysis procedures were robust, although food web transfer of CoTS DNA cannot be ruled out for some fish species. Our results, combined with the (i) presence of CoTS spines in some samples, (ii) reported predation on CoTS gametes, larvae and settled individuals, and (iii) known diet information for fish species examined, strongly indicate that direct fish predation on CoTS may well be more common than is currently appreciated. We provide recommendations for specific management approaches to enhance predation on CoTS by coral reef fishes, and to support the mitigation of CoTS outbreaks and reverse declines in hard coral cover.

Effects of light attenuation on the sponge holobiont- implications for dredging management.

Dredging and natural sediment resuspension events can cause high levels of turbidity, reducing the amount of light available for photosynthetic benthic biota. To determine how marine sponges respond to light attenuation, five species were experimentally exposed to a range of light treatments. Tolerance thresholds and capacity for recovery varied markedly amongst species. Whilst light attenuation had no effect on the heterotrophic species Stylissa flabelliformis and Ianthella basta, the phototrophic species Cliona orientalis and Carteriospongia foliascens discoloured (bleached) over a 28 day exposure period to very low light (<0.8 mol photons m-2 d-1). In darkness, both species discoloured within a few days, concomitant with reduced fluorescence yields, chlorophyll concentrations and shifts in their associated microbiomes. The phototrophic species Cymbastela coralliophila was less impacted by light reduction. C. orientalis and C. coralliophila exhibited full recovery under normal light conditions, whilst C. foliascens did not recover and showed high levels of mortality. The light treatments used in the study are directly relevant to conditions that can occur in situ during dredging projects, indicating that light attenuation poses a risk to photosynthetic marine sponges. Examining benthic light levels over temporal scales would enable dredging proponents to be aware of conditions that could impact on sponge physiology.

Recovery from bleaching is mediated by threshold densities of background thermo-tolerant symbiont types in a reef-building coral.

Sensitive molecular analyses show that most corals host a complement of Symbiodinium genotypes that includes thermo-tolerant types in low abundance. While tolerant symbiont types are hypothesized to facilitate tolerance to temperature and recovery from bleaching, empirical data on their distribution and relative abundance in corals under ambient and stress conditions are still rare. We quantified visual bleaching and mortality of coral hosts, along with relative abundance of C- and D-type Symbiodinium cells in 82 Acropora millepora colonies from three locations on the Great Barrier Reef transplanted to a central inshore site over a 13 month period. Our analyses reveal dynamic change in symbiont associations within colonies and among populations over time. Coral bleaching and declines in C- but not D-type symbionts were observed in transplanted corals. Survival and recovery of 25% of corals from one population was associated with either initial D-dominance or an increase in D-type symbionts that could be predicted by a minimum pre-stress D : C ratio of 0.003. One-third of corals from this population became D dominated at the bleached stage despite no initial detection of this symbiont type, but failed to recover and died in mid to late summer. These results provide a predictive threshold minimum density of background D-type symbionts in A. millepora, above which survival following extreme thermal stress is increased.

Zooplankton Growth, Respiration and Grazing on the Australian Margins of the Tropical Indian and Pacific Oceans.

The specific activity of aminoacyl-tRNA synthetases (spAARS), an index of growth rate, and of the electron transport system (spETS), an index of respiration, was measured in three size fractions (73-150 µm, >150 µm and >350 µm) of zooplankton during five cruises to tropical coastal waters of the Kimberley coast (North West Australia) and four cruises to waters of the Great Barrier Reef (GBR; North East Australia). The N-specific biomass of plankton was 3-4-fold higher in the Kimberley than on the GBR in all 3 size classes: Kimberley 1.27, 3.63, 1.94 mg m-3; GBR 0.36, 0.88 and 0.58 mg m-3 in the 73-150 µm, >150 µm and >350 µm size classes, respectively. Similarly, spAARS activity in the Kimberley was greater than that of the GBR: 88.4, 132.2, and 147.6 nmol PPi hr-1 mg protein -1 in the Kimberley compared with 71.7, 82.0 and 83.8 nmol PPi hr-1 mg protein -1 in the GBR, for the 73-150 µm, >150 µm and >350 µm size classes, respectively. Specific ETS activity showed similar differences in scale between the two coasts: 184.6, 148.8 and 92.2 µL O2 hr-1 mg protein-1 in the Kimberley, against 86.5, 88.3 and 71.3 µL O2 hr-1 mg protein-1 in the GBR. On the basis of these measurements, we calculated that >150 µm zooplankton grazing accounted for 7% of primary production in the Kimberley and 8% in GBR waters. Area-specific respiration by >73 µm zooplankton was 7-fold higher in the Kimberley than on the GBR and production by >150 µm zooplankton was of the order of 278 mg C m-2 d-1 in the Kimberley and 42 mg C m-2 d-1 on the GBR. We hypothesize that the much stronger physical forcing on the North West shelf is the principal driver of higher rates in the west than in the east of the continent.

Does ultrasonography accurately diagnose acute cholecystitis? Improving diagnostic accuracy based on a review at a regional hospital.

BACKGROUND: Acute cholecystitis is one of the most common diseases requiring emergency surgery. Ultrasonography is an accurate test for cholelithiasis but has a high false-negative rate for acute cholecystitis. The Murphy sign and laboratory tests performed independently are also not particularly accurate. This study was designed to review the accuracy of ultrasonography for diagnosing acute cholecystitis in a regional hospital. METHODS: We studied all emergency cholecystectomies performed over a 1-year period. All imaging studies were reviewed by a single radiologist, and all pathology was reviewed by a single pathologist. The reviewers were blinded to each other's results. RESULTS: A total of 107 patients required an emergency cholecystectomy in the study period; 83 of them underwent ultrasonography. Interradiologist agreement was 92% for ultrasonography. For cholelithiasis, ultrasonography had 100% sensitivity, 18% specificity, 81% positive predictive value (PPV) and 100% negative predictive value (NPV). For acute cholecystitis, it had 54% sensitivity, 81% specificity, 85% PPV and 47% NPV. All patients had chronic cholecystitis and 67% had acute cholecystitis on histology. When combined with positive Murphy sign and elevated neutrophil count, an ultrasound showing cholelithiasis or acute cholecystitis yielded a sensitivity of 74%, specificity of 62%, PPV of 80% and NPV of 53% for the diagnosis of acute cholecystitis. CONCLUSION: Ultrasonography alone has a high rate of false-negative studies for acute cholecystitis. However, a higher rate of accurate diagnosis can be achieved using a triad of positive Murphy sign, elevated neutrophil count and an ultrasound showing cholelithiasis or cholecystitis.

CONTEXTE: La cholécystite aiguë est l'une des maladies les plus répandues exigeant une chirurgie d'urgence. L'échographie est un test précis pour le dépistage de la cholélithiase, mais elle s'accompagne d'un taux élevé de diagnostics faux-négatifs de cholécystite aiguë. Le signe de Murphy et les analyses de laboratoire effectuées indépendamment ne sont pas non plus particulièrement précis. Cette étude a été conçue pour vérifier la précision de l'échographie dans le diagnostic de la cholécystite aiguë dans un hôpital régional. MÉTHODES: Nous avons passé en revue toutes les cholécystectomies d'urgence effectuées sur une période d'un an. Toutes les épreuves d'imagerie ont été examinées par un seul radiologue et toutes les analyses d'anatomopathologie, par un seul anatomopathologiste. Les examinateurs n'étaient pas au courant de leurs conclusions respectives. RÉSULTATS: En tout, 107 patients ont eu besoin d'une cholécystectomie d'urgence au cours de la période de l'étude; 83 ont subi une échographie. La concordance d'opinion entre les radiologues a été de 92 % en ce qui concerne l'échographie. Pour la cholélithiase, l'échographie a présenté une sensibilité de 100 %, une spécificité de 18 %, une valeur prédictive positive (VPP) de 81 % et une valeur prédictive négative (VPN) de 100 %. En ce qui concerne la cholécystite aiguë, l'échographie a présenté une sensibilité de 54 %, une spécificité de 81 %, une VPP de 85 % et une VPN de 47 %. Tous les patients souffraient de cholécystite chronique et 67 % présentaient une cholécystite aiguë à l'examen histologique. Alliée à un signe de Murphy positif et à une élévation de la numération des neutrophiles, une échographie révélant une cholélithiase ou cholécystite aiguë offrait une sensibilité de 74 %, une spécificité de 62 %, une VPP de 80 % et une VPN de 53 % pour ce qui est du diagnostic de la cholécystite aiguë. CONCLUSION: L'échographie seule a donné lieu à un taux élevé de diagnostics fauxnégatifs de la cholécystite aiguë. Toutefois, la précision diagnostique augmente lorsque l'on observe simultanément un signe de Murphy positif, une augmentation de la numération des neutrophiles et des signes de cholélithiase cholécystite aiguë à l'échographie.

Phylogeny drives large scale patterns in Australian marine bioactivity and provides a new chemical ecology rationale for future biodiscovery.

Twenty-five years of Australian marine bioresources collecting and research by the Australian Institute of Marine Science (AIMS) has explored the breadth of latitudinally and longitudinally diverse marine habitats that comprise Australia's ocean territory. The resulting AIMS Bioresources Library and associated relational database integrate biodiversity with bioactivity data, and these resources were mined to retrospectively assess biogeographic, taxonomic and phylogenetic patterns in cytotoxic, antimicrobial, and central nervous system (CNS)-protective bioactivity. While the bioassays used were originally chosen to be indicative of pharmaceutically relevant bioactivity, the results have qualified ecological relevance regarding secondary metabolism. In general, metazoan phyla along the deuterostome phylogenetic pathway (eg to Chordata) and their ancestors (eg Porifera and Cnidaria) had higher percentages of bioactive samples in the assays examined. While taxonomy at the phylum level and higher-order phylogeny groupings helped account for observed trends, taxonomy to genus did not resolve the trends any further. In addition, the results did not identify any biogeographic bioactivity hotspots that correlated with biodiversity hotspots. We conclude with a hypothesis that high-level phylogeny, and therefore the metabolic machinery available to an organism, is a major determinant of bioactivity, while habitat diversity and ecological circumstance are possible drivers in the activation of this machinery and bioactive secondary metabolism. This study supports the strategy of targeting phyla from the deuterostome lineage (including ancestral phyla) from biodiverse marine habitats and ecological niches, in future biodiscovery, at least that which is focused on vertebrate (including human) health.

Metabolomic profiles are gender, disease and time specific in the interleukin-10 gene-deficient mouse model of inflammatory bowel disease.

Metabolomic profiling can be used to study disease-induced changes in inflammatory bowel diseases (IBD). The aim of this study was to investigate the difference in the metabolomic profile of males and females as they developed IBD. Using the IL-10 gene-deficient mouse model of IBD and wild-type mice, urine at age 4, 6, 8, 12, 16, and 20 weeks was collected and analyzed by nuclear magnetic resonance (NMR) spectroscopy. Multivariate data analysis was employed to assess differences in metabolomic profiles that occurred as a consequence of IBD development and severity (at week 20). These changes were contrasted to those that occurred as a consequence of gender. Our results demonstrate that both IL-10 gene-deficient and wild-type mice exhibit gender-related changes in urinary metabolomic profile over time. Some male-female separating metabolites are common to both IL-10 gene-deficient and control wild-type mice and, therefore, appear to be related predominantly to gender maturation. In addition, we were able to identify gender-separating metabolites that are unique for IL-10 gene-deficient and wild-type mice and, therefore, may be indicative of a gender-specific involvement in the development and severity of the intestinal inflammation. The comparison of the gender-separating metabolomic profile from IL-10 gene-deficient mice and wild-type mice during the development of IBD allowed us to identify changes in profile patterns that appear to be imperative in the development of intestinal inflammation, but yet central to gender-related differences in IBD development. The knowledge of metabolomic profile differences by gender and by disease severity has potential clinical implications in the design of both biomarkers of disease as well as the development of optimal therapies.

Small bowel fibrosis and systemic inflammatory response after ileocolonic anastomosis in IL-10 null mice.

BACKGROUND: Crohn's disease recurrence after an ileocecal resection is common; yet, its pathophysiology is poorly understood and available treatment is suboptimal. The purpose of this study was to examine the bacterial, local, and systemic immune changes that follow ileocolonic anastomosis in a rodent model of Crohn's disease, the interleukin-10 gene-deficient (IL-10 null) mice. MATERIALS AND METHODS: We divided wild-type and IL-10 null mice into three treatment groups: ileocolonic anastomosis, sham operation (ileo-ileal anastomosis), and control group without an operation. We sacrificed mice at 6 and 15 wks after the operation. At 6 wks, we assessed bacterial changes using the denaturing gel electrophoresis and similarity coefficient calculation. At both time points, we examined the small bowel for inflammation and fibrosis with histology. We measured the interferon gamma secretion by splenocytes stimulated with gastrointestinal bacterial antigens and splenocyte composition as a marker of systemic response. RESULTS: At 6 wks, ileocolonic anastomosis resulted in increased similarity in bacterial species between the ileum and colon. The ileocolonic anastomosis did not lead to significant inflammation in the small intestine, but it resulted in an increased collagen deposition in all animals undergoing surgery, the most pronounced fibrosis of which was present in IL-10 null mice 15 wks after ileocolonic anastomosis. Furthermore, this was associated with significantly increased interferon gamma secretion by bacterial antigen-stimulated splenocytes and a decreased number of CD11+ cells in the same experimental group. CONCLUSIONS: Ileocolonic anastomosis leads to bacterial changes in the terminal ileum. In the genetically susceptible host, it is associated with small bowel fibrosis and systemic immune alterations. The composition of immune cells in the spleen is altered and splenocytes hypersecrete proinflammatory cytokine (interferon gamma) when challenged with gastrointestinal bacterial antigens.

Intravenous injection of endogenous microbial components abrogates DSS-induced colitis.

BACKGROUND: The etiology of inflammatory bowel diseases (IBD) is largely unknown, but appears to be perpetuated by uncontrolled responses to antigenic components of the endogenous flora. Tolerance to antigenic stimulation can be achieved by exposure to a given antigen in high amounts (high dose tolerance). Colitis induced by feeding of Dextran Sodium Sulfate (DSS) is an often-used animal model mimicking clinical and histological features of human IBD. AIMS: We investigated whether treatment with high doses of endogenous bacterial components can affect the response to these antigenic components and thus impact the course of the inflammatory response induced by DSS. METHODS: 129/SvEv mice were injected intravenously in the tail vein with lysates prepared from fecal material of conventionally-raised mice. Control mice received a solution of bacterial antigen-free lysates prepared from fecal material of germ-free mice. Seven days later, colitis was induced in these mice by introducing DSS (3.5%) in the drinking water for 5 days. Onset and course of the inflammatory response was monitored by assessment of weight loss. Mice were sacrificed at day 7 post colitis induction and tested for histopathologic injury, intestinal cytokine release, and systemic response to bacterial antigens. RESULTS: Intravenous injection with fecal lysates reduced intestinal and antigen-stimulated systemic pro-inflammatory cytokine release and prevented DSS-induced weight loss and intestinal injury. CONCLUSION: Pretreatment with high amount of endogenous bacterial components has a profound tolerogenic effect on the systemic and mucosal immune responses resulting in reduced intestinal inflammation and abrogates colitis-induced weight loss.

Environmental factors controlling the distribution of symbiodinium harboured by the coral Acropora millepora on the Great Barrier Reef.

BACKGROUND: The Symbiodinium community associated with scleractinian corals is widely considered to be shaped by seawater temperature, as the coral's upper temperature tolerance is largely contingent on the Symbiodinium types harboured. Few studies have challenged this paradigm as knowledge of other environmental drivers on the distribution of Symbiodinium is limited. Here, we examine the influence of a range of environmental variables on the distribution of Symbiodinium associated with Acropora millepora collected from 47 coral reefs spanning 1,400 km on the Great Barrier Reef (GBR), Australia. METHODOLOGY/PRINCIPAL FINDINGS: The environmental data included Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data at 1 km spatial resolution from which a number of sea surface temperature (SST) and water quality metrics were derived. In addition, the carbonate and mud composition of sediments were incorporated into the analysis along with in situ water quality samples for a subset of locations. Analyses were conducted at three spatio-temporal scales [GBR (regional-scale), Whitsunday Islands (local-scale) and Keppel Islands/Trunk Reef (temporal)] to examine the effects of scale on the distribution patterns. While SST metrics were important drivers of the distribution of Symbiodinium types at regional and temporal scales, our results demonstrate that spatial variability in water quality correlates significantly with Symbiodinium distribution at local scales. Background levels of Symbiodinium types were greatest at turbid inshore locations of the Whitsunday Islands where SST predictors were not as important. This was not the case at regional scales where combinations of mud and carbonate sediment content coupled with SST anomalies and mean summer SST explained 51.3% of the variation in dominant Symbiodinium communities. CONCLUSIONS/SIGNIFICANCE: Reef corals may respond to global-scale stressors such as climate change through changes in their resident symbiont communities, however, management of local-scale stressors such as altered water quality is also necessary for maintenance of coral-Symbiodinium associations.

Neonatal exposure to fecal antigens reduces intestinal inflammation.

BACKGROUND: A role for bacterial antigens in the pathogenesis of inflammatory bowel disease (IBD) has been established in enhanced humoral and cellular immune response to ubiquitous antigens of the enteric flora. However, we have recently shown that bacterial antigens in the absence of live bacteria cannot initiate an intestinal inflammation in IBD-prone interleukin (IL)-10 gene-deficient mice. The objective was to investigate whether neonatal exposure to antigens of their own endogenous flora can tolerize mice to bacterial antigens. METHODS: IL-10 gene-deficient neonates were injected intraperitoneally within 72 hours of birth with a sterile solution of bacterial lysates prepared from fecal material of either conventionally raised mice (contains bacterial antigens) or axenic mice (lacks bacterial antigens). The onset of intestinal inflammation was monitored as the appearance of occult blood in the stool in weekly hemoccult analysis. Mice were sacrificed between age 15 and 19 weeks and tested for histopathologic injury, intestinal inflammation, and systemic response to bacterial antigens. RESULTS: In mice neonatally exposed to bacterial antigens the onset of intestinal inflammation was delayed and the incidence of histopathologic injury at age 18 weeks was reduced. In addition, mice injected with lysates from conventionally raised mice exhibited decreased release of proinflammatory cytokines (interferon gamma [IFN-γ] and IL-17) in intestinal tissue and demonstrated reduced bacteria-stimulated systemic responses when compared to mice injected with lysates derived from bacteria-free, axenic mice. CONCLUSIONS: Neonatal intraperitoneal injection of antigens from the commensal flora causes long-lasting changes in systemic and mucosal immune responses resulting in delayed onset of intestinal inflammation and injury in IBD-prone IL-10 gene-deficient mice.

Characterisation of nitric oxide synthase in three cnidarian-dinoflagellate symbioses.

BACKGROUND: Nitric oxide synthase (NOS) is an enzyme catalysing the conversion of L-arginine to L-citrulline and nitric oxide (NO), the latter being an essential messenger molecule for a range of biological processes. Whilst its role in higher vertebrates is well understood little is known about the role of this enzyme in early metazoan groups. For instance, NOS-mediated signalling has been associated with Cnidaria-algal symbioses, however controversy remains about the contribution of enzyme activities by the individual partners of these mutualistic relationships. METHODOLOGY/PRINCIPAL FINDINGS: Using a modified citrulline assay we successfully measured NOS activity in three cnidarian-algal symbioses: the sea anemone Aiptasia pallida, the hard coral Acropora millepora, and the soft coral Lobophytum pauciflorum, so demonstrating a wide distribution of this enzyme in the phylum Cnidaria. Further biochemical (citrulline assay) and histochemical (NADPH-diaphorase) investigations of NOS in the host tissue of L. pauciflorum revealed the cytosolic and calcium dependent nature of this enzyme and its in situ localisation within the coral's gastrodermal tissue, the innermost layer of the body wall bearing the symbiotic algae. Interestingly, enzyme activity could not be detected in symbionts freshly isolated from the cnidarians, or in cultured algal symbionts. CONCLUSIONS/SIGNIFICANCE: These results suggest that NOS-mediated NO release may be host-derived, a finding that has the potential to further refine our understanding of signalling events in cnidarian-algal symbioses.

Oral administration of curcumin emulsified in carboxymethyl cellulose has a potent anti-inflammatory effect in the IL-10 gene-deficient mouse model of IBD.

Curcumin is a tumeric-derived, water-insoluble polyphenol with potential beneficial health effects for humans. It has been shown to have preventive as well as therapeutic effects in chemically induced murine models of colitis. To investigate whether curcumin exerts a similar effect on the spontaneous colitis in interleukin (IL)-10 gene-deficient mice, we gavaged these mice daily for 2 weeks with 200 mg/kg per day curcumin emulsified in carboxymethyl cellulose, a food additive generally used as a viscosity modifier. Mice fed the curcumin/carboxymethyl cellulose mixture and those receiving carboxymethyl cellulose alone demonstrated similar reductions in histological injury score and colon weight/length ratio compared to water-fed controls. However, significant reductions in pro-inflammatory cytokine release in intestinal explant cultures were only seen in mice treated with the curcumin mixture. Our data demonstrate that in IL-10 gene-deficient mice, both oral curcumin and carboxymethyl cellulose, appear to have modifying effects on colitis. However, curcumin has additional anti-inflammatory effects mediated through a reduced production of potent pro-inflammatory mucosal cytokines.

Eusynstyelamides A, B, and C, nNOS inhibitors, from the ascidian Eusynstyela latericius.

Eusynstyelamides A-C (1-3) were isolated from the Great Barrier Reef ascidian Eusynstyela latericius, together with the known metabolites homarine and trigonelline. The structures of 1-3, with relative configurations, were elucidated by interpretation of their spectroscopic data (NMR, MS, UV, IR, and CD). The NMR data of 1 were found to be virtually identical to that reported for eusynstyelamide (4), isolated from E. misakiensis, indicating that a revision of the structure of 4 is needed. Eusynstyelamides A-C exhibited inhibitory activity against neuronal nitric oxide synthase (nNOS), with IC(50) values of 41.7, 4.3, and 5.8 microM, respectively, whereas they were found to be nontoxic toward the three human tumor cell lines MCF-7 (breast), SF-268 (CNS), and H-460 (lung). Compounds 1 and 2 displayed mild inhibitory activity toward Staphylococcus aureus (IC(50) 5.6 and 6.5 mM, respectively) and mild inhibitory activity toward the C(4) plant regulatory enzyme pyruvate phosphate dikinase (PPDK) (IC(50) values of 19 and 20 mM, respectively).

Vibrio zinc-metalloprotease causes photoinactivation of coral endosymbionts and coral tissue lesions.

BACKGROUND: Coral diseases are emerging as a serious threat to coral reefs worldwide. Of nine coral infectious diseases, whose pathogens have been characterized, six are caused by agents from the family Vibrionacae, raising questions as to their origin and role in coral disease aetiology. METHODOLOGY/PRINCIPAL FINDINGS: Here we report on a Vibrio zinc-metalloprotease causing rapid photoinactivation of susceptible Symbiodinium endosymbionts followed by lesions in coral tissue. Symbiodinium photosystem II inactivation was diagnosed by an imaging pulse amplitude modulation fluorometer in two bioassays, performed by exposing Symbiodinium cells and coral juveniles to non-inhibited and EDTA-inhibited supernatants derived from coral white syndrome pathogens. CONCLUSION/SIGNIFICANCE: These findings demonstrate a common virulence factor from four phylogenetically related coral pathogens, suggesting that zinc-metalloproteases may play an important role in Vibrio pathogenicity in scleractinian corals.