Showing papers on "Oyster published in 2021"

The Pacific Oyster Mortality Syndrome, a Polymicrobial and Multifactorial Disease: State of Knowledge and Future Directions.

Abstract: The Pacific oyster (Crassostreae gigas) has been introduced from Asia to numerous countries around the world during the 20th century. C. gigas is the main oyster species farmed worldwide, and represents more than 98% of oyster production. The severity of disease outbreaks that affect C. gigas, which primarily impact juvenile oysters, has increased dramatically since 2008. The most prevalent disease, Pacific oyster mortality syndrome (POMS), has become panzootic and represents a threat to the oyster industry. Recently, major steps towards understanding POMS have been achieved through integrative molecular approaches. These studies demonstrated that infection by Ostreid herpesvirus type 1 µVar (OsHV-1 µvar) is the first critical step in the infectious process, and leads to an immunocompromised state by altering hemocyte physiology. This is followed by dysbiosis of the microbiota, which leads to a secondary colonization by opportunistic bacterial pathogens, which in turn results in oyster death. Host and environmental factors (e.g. oyster genetics and age, temperature, food availability, and microbiota) have been shown to influence POMS permissiveness. However, we still do not understand the mechanisms by which these different factors control disease expression. The present review discusses current knowledge of this polymicrobial and multifactorial disease process, and explores the research avenues that must be investigated to fully elucidate the complexity of POMS. These discoveries will help in decision-making, and will facilitate the development of tools and applied innovations for the sustainable and integrated management of oyster aquaculture.

Construction of a chromosome-level genome and variation map for the Pacific oyster Crassostrea gigas

Abstract: The Pacific oyster (Crassostrea gigas) is a widely distributed marine bivalve of great ecological and economic importance. In this study, we provide a high-quality chromosome-level genome assembled using Pacific Bioscience long reads and Hi-C-based and linkage-map-based scaffolding technologies and a high-resolution variation map constructed using large-scale resequencing analysis. The 586.8 Mb genome consists of 10 pseudochromosome sequences ranging from 38.6 to 78.9 Mb, containing 301 contigs with an N50 size of 3.1 Mb. A total of 30,078 protein-coding genes were predicted, of which 22,757 (75.7%) were high-reliability annotations supported by a homologous match to a curated protein in the SWISS-PROT database or transcript expression. Although a medium level of repeat components (57.2%) was detected, the genomic content of the segmental duplications reached 26.2%, which is the highest among the reported genomes. By whole genome resequencing analysis of 495 Pacific oysters, a comprehensive variation map was built, comprised of 4.78 million single nucleotide polymorphisms, 0.60 million short insertions and deletions, and 49,333 copy number variation regions. The structural variations can lead to an average interindividual genomic divergence of 0.21, indicating their crucial role in shaping the Pacific oyster genome diversity. The large amount of mosaic distributed repeat elements, small variations, and copy number variations indicate that the Pacific oyster is a diploid organism with an extremely high genomic complexity at the intra- and interindividual level. The genome and variation maps can improve our understanding of oyster genome diversity and enrich the resources for oyster molecular evolution, comparative genomics, and genetic research.

Meta-analysis of oyster impacts on coastal biogeochemistry

Abstract: Overfishing, nutrient-fuelled hypoxia and habitat destruction have reduced oyster populations to a fraction of their former abundance. Over the past two decades there has been a widespread effort to restore oyster reefs and develop oyster aquaculture. Yet it remains unclear how re-introduction of large oyster populations will change coastal biogeochemistry. Of particular interest is whether oysters may help offset excess nitrogen loading, which is responsible for widespread coastal water quality degradation, low oxygen conditions and biodiversity declines. Here we used a meta-analysis approach to assess how oysters alter inorganic nutrient cycling, with a focus on nitrogen removal. Additionally, we examined how oysters alter greenhouse gas emissions. We demonstrate that oysters enhance removal of excess nitrogen by stimulating denitrification, promote efficient nutrient recycling and may have a negligible greenhouse gas footprint. Further, oyster reefs and oyster aquaculture appear to have similar biogeochemical function, suggesting the potential for sustainable production of animal protein alongside environmental restoration. Oysters clean nutrient-polluted waters, but their populations have crashed. This study synthesizes research on oyster impacts and finds that they help remove excess nitrogen and promote nutrient recycling without contributing greatly to greenhouse gas emissions.

Ameliorative Effects of Peptides Derived from Oyster (Crassostrea gigas) on Immunomodulatory Function and Gut Microbiota Structure in Cyclophosphamide-Treated Mice.

Abstract: The intestinal flora is recognized as a significant contributor to the immune system. In this research, the protective effects of oyster peptides on immune regulation and intestinal microbiota were investigated in mice treated with cyclophosphamide. The results showed that oyster peptides restored the indexes of thymus, spleen and liver, stimulated cytokines secretion and promoted the relative mRNA levels of Th1/Th2 cytokines (IL-2, IFN-γ, IL-4 and IL-10). The mRNA levels of Occludin, Claudin-1, ZO-1, and Mucin-2 were up-regulated, and the NF-κB signaling pathway was also activated after oyster peptides administration. Furthermore, oyster peptides treatment reduced the proportion of Firmicutes/Bacteroidetes, increased the relative abundance of Alistipes, Lactobacillus, Rikenell and the content of short-chain fatty acids, and reversed the composition of intestinal microflora similar to that of normal mice. In conclusion, oyster peptides effectively ameliorated cyclophosphamide-induced intestinal damage and modified gut microbiota structure in mice, and might be utilized as a beneficial ingredient in functional foods for immune regulation.

Large-scale variation in wave attenuation of oyster reef living shorelines and the influence of inundation duration

Abstract: One of the paramount goals of oyster reef living shorelines is to achieve sustained and adaptive coastal protection, which requires meeting ecological (i.e., develop a self-sustaining oyster population) and engineering (i.e., provide coastal defense) targets. In a large-scale comparison along the Atlantic and Gulf coasts of the United States, the efficacy of various designs of oyster reef living shorelines at providing wave attenuation was evaluated accounting for the ecological limitations of oysters with regard to inundation duration. A critical threshold for intertidal oyster reef establishment is 50% inundation duration. Living shorelines that spent less than one-half of the time ( 50% inundation were considered suitable habitat for oysters, but wave attenuation was similar to controls (no reef; ~5% reduction in wave height). Many of the oyster reef living shoreline approaches therefore failed to optimize the ecological and engineering goals. In both inundation regimes, wave transmission decreased with an increasing freeboard (difference between reef crest elevation and water level), supporting its importance in the wave attenuation capacity of oyster reef living shorelines. However, given that the reef crest elevation (and thus freeboard) should be determined by the inundation duration requirements of oysters, research needs to be refocused on understanding the implications of other reef parameters (e.g., width) for optimizing wave attenuation. A broader understanding of the reef characteristics and seascape contexts that result in effective coastal defense by oyster reefs is needed to inform appropriate design and implementation of oyster-based living shorelines globally.

Decontamination of Listeria monocytogenes in king oyster mushrooms (Pleurotus eryngii) by combined treatments with organic acids, nisin, and ultrasound

Abstract: This study was conducted to evaluate the effectiveness of 1–3% organic acids alone or in combination with 0.1% nisin and/or 40 kHz ultrasound (US) on the reduction of Listeria monocytogenes in king oyster mushrooms stored at 25 °C. While L. monocytogenes in king oyster mushrooms was reduced by 3.01 log CFU g−1 after dipping in 3% malic acid (MA) at 25 °C for 30 min, the application of 40 kHz US and 0.1% nisin resulted in 0.30 and 2.25 log-reductions, respectively. When L. monocytogenes in mushrooms was subjected to a combined treatment with 3% MA, 0.1% nisin, and 40 kHz US at 25 °C for 20–30 min, this bacterium dropped to

Mitigation of Eutrophication and Hypoxia through Oyster Aquaculture: An Ecosystem Model Evaluation off the Pearl River Estuary

Abstract: Shellfish aquaculture has been proposed to abate eutrophication because it can remove nutrients via shellfish filter-feeding. Using a three-dimensional physical-biogeochemical model, we investigate how effective oyster aquaculture can alleviate eutrophication-driven hypoxia off the Pearl River Estuary. Results show that oysters reduce sediment oxygen consumption and thus hypoxia, by reducing both particulate organic matter directly and regenerated nutrients that support new production of organic matter. The hypoxia reduction is largest when oysters are farmed within the upper water of the low-oxygen zone, and the reduction increases with increasing oyster density although oyster growth becomes slower due to food limitation. When oysters are farmed upstream of the hypoxic zone, the farming-induced hypoxia reduction is small and it declines with increasing oyster density because the nutrients released from the farm can increase downstream organic matter production. An oyster farming area of 10 to 200 km2 yields a hypoxic volume reduction of 10% to 78%, equaling the impact of reducing 10% to 60% of river nutrient input. Our results demonstrate that oyster aquaculture can mitigate eutrophication and hypoxia, but its effectiveness depends on the farming location, areal size, and oyster density, and optimal designs must take into account the circulation and biogeochemical characteristics of the specific ecosystem.

Microbiome Analysis Reveals Diversity and Function of Mollicutes Associated with the Eastern Oyster, Crassostrea virginica

Abstract: Marine invertebrate microbiomes play important roles in diverse host and ecological processes. However, a mechanistic understanding of host-microbe interactions is currently available for a small number of model organisms. Here, an integrated taxonomic and functional analysis of the microbiome of the eastern oyster, Crassostrea virginica, was performed using 16S rRNA gene-based amplicon profiling, shotgun metagenomics, and genome-scale metabolic reconstruction. Relatively high variability of the microbiome was observed across individual oysters and among different tissue types. Specifically, a significantly higher alpha diversity was observed in the inner shell than in the gut, gill, mantle, and pallial fluid samples, and a distinct microbiome composition was revealed in the gut compared to other tissues examined in this study. Targeted metagenomic sequencing of the gut microbiota led to further characterization of a dominant bacterial taxon, the class Mollicutes, which was captured by the reconstruction of a metagenome-assembled genome (MAG). Genome-scale metabolic reconstruction of the oyster Mollicutes MAG revealed a reduced set of metabolic functions and a high reliance on the uptake of host-derived nutrients. A chitin degradation and an arginine deiminase pathway were unique to the MAG compared to closely related genomes of Mollicutes isolates, indicating distinct mechanisms of carbon and energy acquisition by the oyster-associated Mollicutes A systematic reanalysis of public eastern oyster-derived microbiome data revealed a high prevalence of the Mollicutes among adult oyster guts and a significantly lower relative abundance of the Mollicutes in oyster larvae and adult oyster biodeposits.IMPORTANCE Despite their biological and ecological significance, a mechanistic characterization of microbiome function is frequently missing from many nonmodel marine invertebrates. As an initial step toward filling this gap for the eastern oyster, Crassostrea virginica, this study provides an integrated taxonomic and functional analysis of the oyster microbiome using samples from a coastal salt pond in August 2017. The study identified high variability of the microbiome across tissue types and among individual oysters, with some dominant taxa showing higher relative abundance in specific tissues. A high prevalence of Mollicutes in the adult oyster gut was revealed by comparative analysis of the gut, biodeposit, and larva microbiomes. Phylogenomic analysis and metabolic reconstruction suggested the oyster-associated Mollicutes is closely related but functionally distinct from Mollicutes isolated from other marine invertebrates. To the best of our knowledge, this study represents the first metagenomics-derived functional inference of Mollicutes in the eastern oyster microbiome.

Effects of Extraction Buffer on the Solubility and Immunoreactivity of the Pacific Oyster Allergens.

Abstract: Despite recent technological advances, novel allergenic protein discovery is limited by their low abundance, often due to specific physical characteristics restricting their recovery during the extraction process from various allergen sources. In this study, eight different extraction buffers were compared for their ability to recover proteins from Pacific oyster (Crassostrea gigas). The protein composition was investigated using high resolution mass spectrometry. The antibody IgE-reactivity of each extract was determined using a pool of serum from five shellfish-allergic patients. Most of the investigated buffers showed good capacity to extract proteins from the Pacific oyster. In general, a higher concentration of proteins was recovered using high salt buffers or high pH buffers, subsequently revealing more IgE-reactive bands on immunoblotting. In contrast, low pH buffers resulted in a poor protein recovery and reduced IgE-reactivity. Discovery of additional IgE-reactive proteins in high salt buffers or high pH buffers was associated with an increase in allergen abundance in the extracts. In conclusion, increasing the ionic strength and pH of the buffer improves the solubility of allergenic proteins during the extraction process for oyster tissue. This strategy could also be applied for other difficult-to-extract allergen sources, thereby yielding an improved allergen panel for increased diagnostic efficiency.

Agricultural by-products and oyster shell as alternative nutrient sources for microbial sealing of early age cracks in mortar.

Abstract: Bio-concrete using bacterially produced calcium carbonate can repair microcracks but is still relatively expensive due to the addition of bacteria, nutrients, and calcium sources. Agricultural by-products and oyster shells were used to produce economical bio-concrete. Sesame meal was the optimal agricultural by-product for low-cost spore production of the alkaliphilic Bacillus miscanthi strain AK13. Transcriptomic dataset was utilized to compare the gene expressions of AK13 strain under neutral and alkaline conditions, which suggested that NaCl and riboflavin could be chosen as growth-promoting factors at alkaline pH. The optimal levels of sesame meal, NaCl, and riboflavin were induced with the central composite design to create an economical medium, in which AK13 strain formed more spores with less price than in commercial sporulation medium. Calcium nitrate obtained from nitric acid treatment of oyster shell powder increased the initial compressive strength of cement mortar. Non-ureolytic calcium carbonate precipitation by AK13 using oyster shell-derived calcium ions was verified by energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. Stereomicroscope and field emission scanning electron microscopy confirmed that oyster shell-derived calcium ions, along with soybean meal-solution, increased the bacterial survival and calcium carbonate precipitation inside mortar cracks. These data suggest the possibility of commercializing bacterial self-healing concrete with economical substitutes for culture medium, growth nutrient, and calcium sources.

Functional plasticity in oyster gut microbiomes along a eutrophication gradient in an urbanized estuary.

Abstract: Oysters in coastal environments are subject to fluctuating environmental conditions that may impact the ecosystem services they provide. Oyster-associated microbiomes are responsible for some of these services, particularly nutrient cycling in benthic habitats. The effects of climate change on host-associated microbiome composition are well-known, but functional changes and how they may impact host physiology and ecosystem functioning are poorly characterized. We investigated how environmental parameters affect oyster-associated microbial community structure and function along a trophic gradient in Narragansett Bay, Rhode Island, USA. Adult eastern oyster, Crassostrea virginica, gut and seawater samples were collected at 5 sites along this estuarine nutrient gradient in August 2017. Samples were analyzed by 16S rRNA gene sequencing to characterize bacterial community structures and metatranscriptomes were sequenced to determine oyster gut microbiome responses to local environments. There were significant differences in bacterial community structure between the eastern oyster gut and water samples, suggesting selection of certain taxa by the oyster host. Increasing salinity, pH, and dissolved oxygen, and decreasing nitrate, nitrite and phosphate concentrations were observed along the North to South gradient. Transcriptionally active bacterial taxa were similar for the different sites, but expression of oyster-associated microbial genes involved in nutrient (nitrogen and phosphorus) cycling varied throughout the Bay, reflecting the local nutrient regimes and prevailing environmental conditions. The observed shifts in microbial community composition and function inform how estuarine conditions affect host-associated microbiomes and their ecosystem services. As the effects of estuarine acidification are expected to increase due to the combined effects of eutrophication, coastal pollution, and climate change, it is important to determine relationships between host health, microbial community structure, and environmental conditions in benthic communities.

Evaluating the Suitability of Baobab Fruit Shells as Substrate for Growing Oyster Mushroom (Pleurotus ostreatus)

Abstract: The baobab fruit shells were evaluated for their suitability as a substrate for growing oyster mushrooms and compared to three base substrates (wheat straw, maize cobs, and sawdust) of 1 kg dry weight. The duration of developmental stages, mycelium vigor, yield, and biological efficiency of the oyster mushroom from the four different substrates were recorded. Yields from the first 3 harvests (flushes) were considered, as they were the most productive ones. Wheat straw demonstrated significantly ( ) higher mycelial colonization rate taking an average of 23 days to complete full spawn run followed by baobab fruit shells, sawdust, and maize cobs which took averages of 25.8, 27.2, and 29.5 days, respectively. Baobab fruit shells had the longest number of days taken between full spawn run and first pinhead formation with an average of 14.4 days which was significantly different ( ) to the wheat straw, sawdust, and maize cobs which had 7.4, 9.4, and 10.5 days. The highest yield was observed on the sawdust which had an average of 682 g followed by wheat straw with 594 g. Maize cobs and baobab fruit shells had the least yield of 518 g and 482 g, respectively. The results showed that baobab fruit shells could be used as a substrate for the cultivation of oyster mushrooms and it can be recommended for commercial cultivation of oyster mushrooms.

Investigating influence of aquaculture seawater with different salinities on non-volatile taste-active compounds in Pacific oyster (Crassostrea gigas)

Abstract: The oyster is well-known for its delicious taste and nutritional benefits. However, the taste of oysters in the market is relatively monotonous at present. In order to develop more tastes of oysters, this study explored the taste compounds (organic-acids, 5′-nucleotides and free amino acids) of Pacific oysters (Crassostrea gigas, triploid oyster) obtained from aquaculture at three different salinities (25‰, 28‰ and 32‰). The results showed that the contents of 5′-nucleotides (52.59 mg/100 g) in the test samples from the aquaculture salinity of 28‰ were higher than those in the salinity of 25‰ and 32‰. The contents of free amino acids (1760.47 mg/100 g) in the 32‰ sample were higher than those in the salinity of 25‰ and 28‰ ones. In addition, the taste activity value (TAV) and equivalent umami concentration (EUC) of three samples were calculated. The relationship between EUC and sensory evaluation was also investigated. The results showed that the highest TAV of the major free amino acids and 5′-nucleotides was observed in the 28‰ salinity oyster sample. A positive relationship was established between EUC and sensory score of overall taste as well as umami, respectively. Our results suggested that 28‰ was the optimal aquaculture salinity with regards to the oyster’s taste, and it was the most commonly accepted. The study may be helpful to guide rational development of diversified flavors of oyster.