Development of a continuous cell line from larval Atlantic cod (Gadus morhua) and its use in the study of the microsporidian,Loma morhua

In vitro cell culture methods are crucial for the isolation, purification and mass propagation of intracellular pathogens of aquatic organisms. Cell culture infection models can yield insights into infection mechanisms, aid in developing methods for disease mitigation and prevention, and inform commercial‐scale cultivation approaches. This study details the establishment of a larval cell line (GML‐5) from the Atlantic cod (Gadus morhua) and its use in the study of microsporidia. GML‐5 has survived over 100 passages in 8 years of culture. The line remains active and viable between 8 and 21°C in Leibovitz‐15 (L‐15) media with 10% foetal bovine serum and exhibits a myofibroblast phenotype as indicated by immuno‐positive results for vimentin, α‐smooth muscle actin, collagen I and S‐100 proteins, while being desmin‐negative. GML‐5 supports the infection and development of two microsporidian parasites, an opportunistic generalist (Anncaliia algerae) and cod‐specific Loma morhua. Using GML‐5, spore germination and proliferation of L. morhua was found to require exposure to basic pH and cool incubation temperatures (8°C), in contrast to A. algerae, which required no cultural modifications. Loma morhua‐associated xenoma‐like structures were observed 2 weeks postexposure. This in vitro infection model may serve as a valuable tool for cod parasitology and aquaculture research.     

Marine-Derived Quorum-Sensing Inhibitory Activities Enhance the Antibacterial Efficacy of Tobramycin against Pseudomonas aeruginosa

Bacterial epiphytes isolated from marine eukaryotes were screened for the production of quorum sensing inhibitory compounds (QSIs). Marine isolate KS8, identified as a Pseudoalteromonas sp., was found to display strong quorum sensing inhibitory (QSI) activity against acyl homoserine lactone (AHL)-based reporter strains Chromobacterium violaceum ATCC 12472 and CV026. KS8 supernatant significantly reduced biofilm biomass during biofilm formation (−63%) and in pre-established, mature P. aeruginosa PAO1 biofilms (−33%). KS8 supernatant also caused a 0.97-log reduction (−89%) and a 2-log reduction (−99%) in PAO1 biofilm viable counts in the biofilm formation assay and the biofilm eradication assay respectively. The crude organic extract of KS8 had a minimum inhibitory concentration (MIC) of 2 mg/mL against PAO1 but no minimum bactericidal concentration (MBC) was observed over the concentration range tested (MBC > 16 mg/mL). Sub-MIC concentrations (1 mg/mL) of KS8 crude organic extract significantly reduced the quorum sensing (QS)-dependent production of both pyoverdin and pyocyanin in P. aeruginosa PAO1 without affecting growth. A combinatorial approach using tobramycin and the crude organic extract at 1 mg/mL against planktonic P. aeruginosa PAO1 was found to increase the efficacy of tobramycin ten-fold, decreasing the MIC from 0.75 to 0.075 µg/mL. These data support the validity of approaches combining conventional antibiotic therapy with non-antibiotic compounds to improve the efficacy of current treatments.     

Factors affecting adoption of hedgerows and other biodiversity-enhancing features on farms in California, USA

Although hedgerows, windbreaks, and other biodiversity-enhancing farm edge features offer the potential for ecosystem benefits without occupying much crop space, relatively few farms in California, USA include such features. Our study identified the practices currently used to manage non-cropped edges of fields, ponds, and watercourses in a case study area in California. We also identified social, economic, and agronomic incentives and constraints to installing biodiversity-enhancing edge features. More than one-third of the study farmers had installed native hedgerows, windbreaks, and/or grassed edges. Interviews demonstrated the importance of socially influential farmers working in tandem with public and private agencies to build initial interest in these practices. However, these features occupied less than four percent of all possible edge length. Constraints to increasing adoption included high costs, fear of harbouring weeds and rodents, and lack of certainty about ecosystems benefits, highlighting the need for cost-share programs and more regionally-focused agroecological research.     

Alternative modes of governance: organic as civic engagement

A major strategy in the creation of sustainable economies is the establishment of alternative market institutions, such as fair trade and local market systems. However, the dynamics of these alternative markets are poorly understood. What are the rules of behavior by which these markets function? How do these markets maintain their separate identity as “alternative”: apart from the conventional (“free”) market system? Building on Lyson’s notion of civic agriculture, we argue that alternative markets maintain themselves through civic engagement. However, we argue that the civically-engaged practices of alternative markets are poorly understood. We seek, therefore, to begin a conversation about the everyday forms of civic engagement in alternative practice and to do this we introduce a few useful conceptual tools. Building upon ideas in science studies about the collaboration of scientists (Hess, Alternative pathways in science and industry, 2007) we argue that civic markets have their own “market fields” and “modes of governance” (Bulkeley et al., Environment and Planning A 39:2733–2753, 2007), their own fields of social interaction in which rules of behavior become stabilized and determine how the market works. The creation of a social field also requires the demarcation of boundaries, referred to in the science studies literature as “boundary work” (Gieryn, Cultural boundaries of science: Credibility on the line, 1999). We apply the idea of boundary work to understand how alternative market actors maintain boundaries between alternative and conventional markets. Finally, studies of collaboration in science have often centered on the object created through these interactions, an object that is partially material and partially a product of knowledge, what (Rheinberger, Toward a history of epistemic things: Synthesizing proteins in the test tube, 1997) calls an “epistemic object.” We use this idea to understand that the creation of alternative objects of exchange, such as organic food, are epistemic objects in that they combine both particular materialities and particular ways of knowing. Using these concepts, we will carry out a close analysis of the mode of governance in the national organic market, looking specifically a recent governance crisis in organic agriculture known as the Harvey lawsuit.     

Optimal harvesting strategies: Practice versus theory

Abstract

Over the last decade or so, a number of bioeconomic models have been developed with the expressed objective of identifying the optimal time to harvest farmed fish. The models explicitly incorporate growth rates, prices and costs, but have generally excluded risk except implicitly through the discount rate. Implicit in this is the assumption that risk is continuous, such that the probability of significant changes in key parameters (e.g. prices, mortality rates etc) is independent of time. In reality, these factors can vary over time. In this paper, the optimal harvesting strategies for two farmed species were analysed using a bioeconomic model. The model was based on previous models applied in the literature, with a new feed‐use component applied. The theoretical ‘optimal’ harvest strategy was compared with actual behaviour, and the factors that may affect divergences in the results examined.     

Within-field variability of Fusarium head blight pathogens and their associated mycotoxins

Within-field variability in the Fusarium head blight (FHB) and its associated mycotoxins was studied in four European countries. At each of 14 sites, each FHB pathogen and associated mycotoxins were quantified in 16 quadrat samples at harvest. Overall, the incidence of quadrat samples with detectable and quantifiable pathogen DNA was significantly lower in the grain than in the corresponding chaff. Deoxynivalenol (DON) was the most frequently detected toxin in the samples and its accumulation was most strongly associated with the presence of Fusarium graminearum. Nivalenol (NIV) accumulation was significantly associated only with the presence of F. culmorum. Zearalenone (ZON) accumulation was strongly associated with the presence of all three pathogens (F. graminearum, F. culmorum and F. poae). The levels of both DON and ZON concentrations were positively related to the amount of F. graminearum DNA in the grain or in the chaff. The presence/absence of FHB pathogens within a single quadrat appeared to be independent of each other. The presence of a particular FHB pathogen and the amount of its DNA, as well as the associated mycotoxin(s), varied greatly among samples at each site. This study demonstrated the large extent of within-field variability of FHB and its associated mycotoxins, and the importance of representative sampling in FHB studies.     

Effects of nitrogen,phosphorus, and potassium on SPAD-502 and atLEAF sensor readings of Salvia

There are various optical sensors in the market for precision nitrogen (N) management, which estimate leaf N status from chlorophyll content of leaves. However, readings may also be affected by the amounts of other nutrients in the plant leaves like potassium (K) and phosphorus (P), as well as sampling location within a plant or leaf. SPAD-502 and atLEAF optical sensors were used on Salvia ‘Vista Red’ plants grown with 0N-7.9P-0K, 41N-0P-0K, 0N-0P-31.6K, 0N-7.9P-0K + 41N-0P-0K, 0N-7.9P-0K + 0N-0P-31.6K, 41N-0P-0K + 0N-0P-31.6K, or 0N-7.9P-0K + 41N-0P-0K + 0N-0P-31.6K fertilizer plus a control. Both sensors were correlated with leaf N and each other. However, both sensor readings were affected by the presence or absence of P and K in the leaves, and thus these nutrients should be analyzed and reported along with leaf N values. Sensor readings were found to vary within a leaf and within leaf canopy location, so sampling needs to be consistent.