2,303 research outputs found
What do the terms resistance, tolerance, and resilience mean in the case of Ostrea edulis infected by the haplosporidian parasite Bonamia ostreae
Full text linkThe decline of the European flat oyster Ostrea edulis represents a loss to European coastal economies both in terms of food security and by affecting the Good Environmental Status of the marine environment as set out by the European Council's Marine Strategy Framework Directive (2008/56/EC). Restoration of O. edulis habitat is being widely discussed across Europe, addressing key challenges such as the devastating impact of the haplosporidian parasite Bonamia ostreae. The use of resistant, tolerant, or resilient oysters as restoration broodstock has been proposed by restoration practitioners, but the definitions and implications of these superficially familiar terms have yet to be defined and agreed by all stakeholders. This opinion piece considers the challenges of differentiating Bonamia resistance, tolerance, and resilience; challenges which impede the adoption of robust definitions. We argue that, disease-resistance is reduced susceptibility to infection by the parasite, or active suppression of the parasites ability to multiply and proliferate. Disease-tolerance is the retention of fitness and an ability to neutralise the virulence of the parasite. Disease-resilience is the ability to recover from illness and, at population level, tolerance could be interpreted as resilience. We concede that further work is required to resolve practical uncertainty in applying these definitions, and argue for a collaboration of experts to achieve consensus. Failure to act now might result in the future dispersal of this disease into new locations and populations, because robust definitions are important components of regulatory mechanisms that underpin marine management.</p
New technologies to enhance resistance to oyster herpes virus
Full text linkAquaculture is the fastest growing farmed food sector in the world and is a key part of global food security, encompassing the farming of fishes, molluscans and crustaceans. The Pacific oyster Crassostrea gigas is a globally important species, farmed commercially across the world. The major threat facing sustainable growth of Pacific oyster aquaculture is the spread of disease, chiefly the pathogenic oyster herpes virus microvariant (OsHV-1 uVar). Biosecurity has so far proven the best way to reduce the impact of OsHV-1, but has not been totally successful as outbreaks have continued to occur where oysters are grown in the open seas.
Vaccination against OsHV-1 is not currently possible as oysters lack a sophisticated adaptive immune system. The cost of OsHV-1 outbreaks is large, both in terms of food and economic losses, and is the focus of research and development worldwide. For example, selective breeding programmes have been used to develop strains of oysters that are more resistant to OsHV-1 through the realisation of genetic improvement. The basis of genetic resistance to OsHV-1 is unclear, although the potential for improvement is promising. However, the
technology available for studying OsHV-1 and implementing practical gains in disease resistance are severely lacking compared to terrestrial livestock and to other aquaculture species, particularly finfish.
Transgenesis and genome editing are powerful tools that have been used to study gene function in a wide range of species and have resulted in development of improved food crops and animals. However, the application of transgenesis and particularly genome editing in marine invertebrates is well behind that of other commercially important animals. Difficulties arise due to lack of basic methods for key processes, such as use of cell cultures, and limited understanding of OsHV-1 pathogenesis. However, aspects of Pacific oyster biology make them well suited to improve these technologies. In particular, oysters can be spawned in controlled environments and produce a vast number of embryos that develop rapidly.
Additionally, the economic importance from being one of the top aquaculture molluscs globally makes them the ideal species through which application of findings has a direct route to impact.
To improve upon the protocols available for producing primary cell cultures, I developed a new large explant method using tissues from adult and juvenile Pacific oysters. Primary cultures were established from heart, mantle, muscle, gill, gonad tissue, as well as hemocytes.
This method had benefits over existing approaches as cultures were maintained for longer (up to 10 weeks) and displayed novel cell morphologies. This new method is logistically simpler than previous methods so that cultures can be established more easily and with fewer specialised reagents. Additionally, this method led to the discovery of entire tissues and large tissue fragments that remained active in the tissue culture system for up to 10 weeks after being excised from the donor animal. Hearts continued to beat rhythmically, mantle tissues continued to move and produce mucus, and gill tissues continue to actively move media surrounding them. This new whole-organ system, as well as the incremental improvements in primary cell culture, could have major benefits for studying marine invertebrate cell culture and potentially for the development of an immortalised marine mollusc cell line.
To further develop the tissue explant system for studying OsHV-1, I made tissue explants taken from juvenile oysters and exposed them to infectious OsHV-1 in a controlled laboratory environment. Using qPCR, histology and electron microscopy I collected strong evidence to support the conclusion that OsHV-1 can replicate in heart, mantle, and gill tissue explants. To further validate the use of tissue explants as a model for OsHV-1 infection, tissue explants were taken from oysters originating from two different oyster producers in the UK, which show
different responses to OsHV-1 in laboratory challenges.
The viral load of the media and within tissues was quantified using qPCR and showed that the source of the oyster influenced the outcome of the tissue explant infection. This work offers a new model for OsHV-1 infection which can be more tightly controlled than existing models, offering the potential to disentangle the complexities of OsHV-1 pathogenesis. This also demonstrates another application for the
whole tissue explant method described earlier.
To improve the methods available for transgenesis in Pacific oysters, I used an iterative approach to compare existing approaches and test new approaches. This is the first work to directly compare different oyster transgenesis methods, which have been limited to cross-species comparisons. By using high throughput methods such as electroporation, lipofection and lentivirus mediated transfection oyster embryos and gametes can be transfected at a scale that is unmatched in either finfish or terrestrial livestock. Using electroporation of a plasmid containing the GFP protein an oyster embryo that was clearly healthy and swimming with a clear and distinct fluorescence was detected. Furthermore, lipofection and lentivirus mediated transfection were attempted in Pacific oysters for the first time. The transfection efficiency using electroporation was very low, and no clear signs of fluorescence was detected using any of the other approaches used. This work highlights the difficulties that exist for molluscan genome engineering but provides the most comprehensive and detailed attempts yet.
To apply the methods developed for transgenesis to genome editing, I used the
electroporation approach to introduce Cas9 ribonucleoprotein designed based on previous successful research that used microinjection. This work also tested a different electroporation system which has some key advantages over the system used for chapter 5. DNA sequencing did not detect clear evidence of genome editing.
Overall, my research has demonstrated significant development in applying genetic engineering and tissue culture methods to the Pacific oyster, with potential for application in marine molluscs broadly. I have also demonstrated for the first time that functional oyster tissues can be maintained in a cell culture system and provide a useful tool for studying OsHV-1
Evaluating Citebase, an open access Web-based citation-ranked search and impact discovery service
No full textCitebase is a new citation-ranked search and impact discovery service that measures citations of scholarly research papers which are openly accessible on the Web, i.e. papers that are assessable continuously online. Other services, such as ResearchIndex, have emerged in recent years to offer citation indexing of Web research papers. In the first detailed user evaluation of an open access Web citation indexing service, Citebase has been evaluated by nearly 200 users from different backgrounds. The paper details the procedures used in the evaluation, and analyses the results of this study, which took place between June and October 2002. It was found that within the scope of its primary components, the search interface and services available from its rich bibliographic records, Citebase can be used simply and reliably for the purpose intended, and that it compares favourably with other bibliographic services. It is shown tasks can be accomplished efficiently with Citebase regardless of the background of the user. More data need to be collected and the process refined before it is as reliable for measuring citation impact of indexed papers. Better explanations and guidance are required for first-time users. Coverage is seen as a limiting factor, even though Citebase indexes over 200,000 papers from arXiv. Non-physicists were frustrated at the lack of papers from other sciences. The principle of citation searching of open access archives has thus been demonstrated and need not be restricted to current users. Since the evaluation, Citebase has become a featured service of the ArXiv physics eprint archives
Author Talk
No full textUniversity president, Jim Schmotter, introduces Tim O'Brien at the author talk in Ives Auditorium, October 26, 2010.</p
Who Belongs? Immigrants, Refugees, Migrants, and Actions Towards Justice: A Conversation With Tim Wise
Full text linkTim Wise is an antiracist activist, essayist and author of seven books on racism, inequality and white privilege. He is among the most prominent anti-racist writers and educators in the United States. Over the past 25 years he has engaged audiences in all 50 states, at over 1000 college and high school campuses, at hundreds of professional and academic conferences, and to community groups across the country. While visiting Iowa State University Tim Wise interviewed with us to discuss Who Belongs? by providing a brief historical perspective of immigration, the current political climate, and the role of activism.</p
Growth and phosphorus uptake of faba bean and cotton are related to Colwell-P concentrations in the subsoil of Vertosols
No full textRecent studies report low and variable phosphorus (P) fertiliser use efficiency (PUE) for cotton in the northern grains region (NGR) of eastern Australia. This may be due to cotton accessing P pools that are not currently tested for in the subsoil (10-30 cm) or variation in response to P source and placement strategy. Two glasshouse studies were used to investigate this, incorporating two soil P tests to assess readily and slowly available P pools (Colwell, and a dilute acid colloquially referred to as the BSES extractant), and five different P fertiliser placement strategies in the subsoil. Eighteen Vertosols were collected across southern to central Queensland in the NGR, and then used to grow faba bean ('Vicia faba' L.) and cotton ('Gossypium hirsutum' L.) sequentially in the same 28-L pot. Readily available P pools assessed by Colwell-P were of major importance for faba bean and cotton dry matter, as well as for tissue P concentrations. Cotton was less responsive to extractable subsoil P concentrations than faba bean, suggesting either greater internal PUE or improved ability to accumulate P under conditions of limited availability. We recommend that subsoil P fertilisation should occur before sowing faba bean to maximise PUE in a cotton-faba bean rotation. Faba bean and cotton both recovered more P when the subsoil was fertilised, but no individual P fertiliser placement strategy was superior. Phosphorus extracted using the BSES method was not correlated with faba bean or cotton dry matter or tissue P concentration over the single crop cycle. We also recommend that Colwell-P be measured in the topsoil and subsoil to understand the quantity of plant-available P in Vertosols of the NGR, and that further research is needed to describe the resupply of the readily available P pool from slowly available P pools during a single crop cycle
The oyster larval microbiome and its manipulation for the improvement of shellfish aquaculture
Full text linkAquaculture is the practice of farming aquatic species and contributes significantly to global
seafood production. Aquaculture production has increased dramatically since the 1950’s, and with this, so has the production of molluscs. Oysters make up the most commonly produced group of molluscs by quantity, being produced for both food sustainability and ecological restoration goals. Importantly, the security and expansion of oyster farming is reliant upon reliable production of good quality seedstock from hatcheries. The production of such seedstock is, however, greatly hindered by large-scale disease mortality events that often occur during the larval stages of the oyster lifecycle. The causes of these disease mortality events are known to be often caused by dysbiosis of the larval microbiome (the collection of microorganisms including bacteria, viruses and fungi that live within the larvae and their environment). It is also is well accepted that the microbiome plays a key role in maintaining larval health. Research into the bacteria that reside within oyster larvae and their environments is therefore vital to understand larval health and improve the ways in which they are farmed. This research is also of benefit to aquaculture generally with methods of improving oyster aquaculture being possibly applicable to other key bivalve species such as mussels, scallops or clams. Within a broader context still, the improvement of oyster aquaculture is beneficial to restoration efforts, where increased oyster production allows for the improvement of water quality, substrate stabilisation and increased biodiversity in coastal ecosystems.
This thesis aims to improve the current understanding of the larval microbiome and
investigate possible methods of microbial manipulation for improved larval heath within the
hatchery setting. Chapter two addressed this with an environmental microbiome study of the European flat oyster (Ostrea edulis). This was done via the collection of water samples taken throughout a natural spawning event of O. edulis at Loch Ryan, UK. It was reported that microbial changes within this spawning event were most closely correlated with date and driven by the differences in abundance of certain bacterial taxa such as those belonging to the Rhodobacteraceae family. Inverse abundance profiles were also observed between bacteria belonging to the Rhodobacteraceae family and Vibrio genera. With species of the Vibrio genera being known to cause disease mortality events in larvae, this finding allowed for the formation of a hypothesis that Sulfitobacter and Jannaschia genera of Rhodobacteraceae may be suitable probiotic candidates for usage within oyster hatcheries. This hypothesis was tested through both bacterial plate assays and in vivo challenges in adult oysters throughout chapter five. Although preliminary, these challenges provided promising data. Most importantly, the addition of Rhodobacteraceae to seawater improved oyster survival rate when challenged with Vibrio aestuarianus. This finding has possible applications to improving oyster heath and cultivation. Chapter five also discusses future experimental work needed to replicate these findings within larger sample sets.
Similarly, chapter three was carried out with the ultimate aim of improving larval health
within the hatchery environment for improved oyster production. This chapter again uses full-length 16S rRNA sequencing to provide baseline bacterial profiles throughout commercial
production at two different UK hatcheries, covering species of both O. edulis (produced at
Portsmouth) and Crassostrea gigas (C. gigas, produced at Morecambe Bay). The core larval
microbiomes from each hatchery were identified and microbial species richness tended to
decrease as the larvae developed. Microbial profiles of larvae were also found to be distinct
to that of their surrounding water. This broad-scale microbial data also allowed for the
microbial implications of hatchery practices to be discussed with water filtration techniques
at both locations being successful in reducing bacterial diversity within the water samples.
Generally, this chapter improves the current understanding of the larval microbiome and their
hatchery environment whilst also fulfilling a knowledge gap by conducting this research
throughout commercial production.
Chapter four builds upon previous baseline data by investigating possible methods of
microbiome manipulation to improve larval health and negate the need for antibiotic usage
within hatcheries. The growth rates of larvae which were reared up to 15-days post
fertilisation under different diet and treatment groups were collected. Microbial comparisons
were also reported via both culture dependent and independent techniques. Most notably,
the microbiomes of larvae grown under two different dietary treatments were found to be
distinct from one another, with differences being driven by the abundance of bacterial taxa
such as Actinobacteria, Bdellovibrionia and Bacilli.
In summary, this thesis provides vital baseline data about the O. edulis and C. gigas larval
microbiomes throughout a range of different spawning types and locations. This has allowed
for an improved understanding of the larval microbiome which is vital in order to better
inform hatchery practices and improve production. Chapters four and five build upon the
previous broad-scale data collected in two and three by demonstrating possible methods of
targeted microbial manipulation
Faba bean fertiliser trial – Spring Ridge 2016
No full textTo study the effect of nitrogen (N) and phosphorus (P) application separately and in combination on the growth and yield of faba bean.<br/>This experiment aimed to study the effect of nitrogen (N) and phosphorus (P) application separately and in combination on the growth and yield of faba bean. A small amount of N at sowing might improve yield through faster establishment and groundcover. There is also little local data available on faba bean response to additional P
Accepting Optimally in Automated Negotiation with Incomplete Information (abstract)
No full textIntelligent SystemsElectrical Engineering, Mathematics and Computer Scienc
Whose Voice? Tim Crouch’s The Author and Active Listening on the Contemporary Stage
No full textThe essay discusses Tim Crouch’s recent play The Author (2009) in the context of active listening, audience participation, response and responsibility in contemporary theatre. It provides a critical engagement with the spectatorial experience of the piece so as to problematize the multiple uses of the physical medium of voice and speech in a contemporary play that delivers a fresh angle to narrativity and metatheatricality. At the same time, the essay probes the varied range of possibilities but also realistic extent of audience involvement in the play, tracing its deep textual contingencies to produce an overall understanding of the equally rewarding and precarious interrelationship between performance piece and audience.</p
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