Rearing Water Treatment Induces Microbial Selection Influencing the Microbiota and Pathogen Associated Transcripts of Cod (Gadus morhua) Larvae

We have previously shown that K-selection and microbial stability in the rearing water increases survival and growth of Atlantic cod (Gadus morhua) larvae, and that recirculating aquaculture systems (RAS) are compatible with this. Here, we have assessed how water treatment influenced the larval microbiota and host responses at the gene expression level. Cod larvae were reared with two different rearing water systems: a RAS and a flow-through system (FTS). The water microbiota was examined using a 16S rDNA PCR/DGGE strategy. RNA extracted from larvae at 8, 13, and 17 days post hatching was used for microbiota and microarray gene expression analysis. Bacterial cDNA was synthesized and used for 16S rRNA amplicon 454 pyrosequencing of larval microbiota. Both water and larval microbiota differed significantly between the systems, and the larval microbiota appeared to become more dissimilar between systems with time. In total 4 phyla were identified for all larvae: Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The most profound difference in larval microbiota was a high abundance of Arcobacter (Epsilonproteobacteria) in FTS larvae (34 ± 9% of total reads). Arcobacter includes several species that are known pathogens for humans and animals. Cod larval transcriptome responses were investigated using an oligonucleotide gene expression microarray covering approximately 24,000 genes. Interestingly, FTS larvae transcriptional profiles revealed an overrepresentation of upregulated transcripts associated with responses to pathogens and infections, such as c1ql3-like, pglyrp-2-like and zg16, compared to RAS larvae. In conclusion, distinct water treatment systems induced differences in the larval microbiota. FTS larvae showed up-regulation of transcripts associated with responses to microbial stress. These results are consistent with the hypothesis that RAS promotes K-selection and microbial stability by maintaining a microbial load close to the carrying capacity of the system, and ensuring long retention times for both bacteria and water in the system

Large-Scale Events as Catalysts for Creating Mutual Dependence Between Social Ventures and Resource Providers

We examine the resource mobilization efforts undertaken by a social venture to organize the 2003 Special Olympics World Summer Games and bring about a change in social attitudes towards the cause of learning and intellectual disabilities. In contrast to previously advanced views of social ventures as powerless actors, we find instead that they are able to leverage the visibility afforded by large-scale events to create positions of mutual dependence, which allow them to access broad support bases and assert themselves in relationships with external parties. Specifically, we find that resource mobilization involves six distinct tactics rooted in the softer forms of power, namely, attraction and inducement. The use of these soft-power tactics depends upon the social venture’s goal at different moments of the relationship with its partners and the level of support available from each external party. Our elaborated theory highlights both the role and limitations of soft power in mobilizing resources and managing relationships