Commensal and Opportunistic Bacteria Present in the Microbiota in Atlantic Cod () Larvae Differentially Alter the Hosts' Innate Immune Responses.

The roles of host-associated bacteria have gained attention lately, and we now recognise that the microbiota is essential in processes such as digestion, development of the immune system and gut function. In this study, Atlantic cod larvae were reared under germ-free, gnotobiotic and conventional conditions. Water and fish microbiota were characterised by 16S rRNA gene analyses.

Bacterial community assembly in Atlantic cod larvae (Gadus morhua): contributions of ecological processes and metacommunity structure.

Many studies demonstrate the importance of the commensal microbiomes to animal health and development. However, the initial community assembly process is poorly understood. It is unclear to what extent the hosts select for their commensal microbiota, whether stochastic processes contribute, and how environmental conditions affect the community assembly.

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

We have previously shown that K-selection and microbial stability in the rearing water increases survival and growth of Atlantic cod () 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).

Bacterial composition and activity determines host gene-expression responses in gnotobiotic Atlantic cod (Gadus morhua) larvae.

In this study the effects of different live versus dead bacteria on the survival and gene-expression patterns in Atlantic cod (Gadus morhua) larvae were examined. Seventeen different gnotobiotic conditions were tested in a 5-day experiment, and the effects of these conditions on the expression of selected genes involved in immune response, xenobiotic breakdown and nutrition (C3, Gpx, Cyp1a1 and Fdps) were investigated. For some of the conditions where dead bacteria were added, we observed significantly higher survival compared to the axenic control.