Differential protein expression in early Atlantic cod larvae (Gadus morhua) in response to treatment with probiotic bacteria.

Proteome analysis was used to study the effects of probiotic bacteria treatment on the protein expression in early Atlantic cod (Gadus morhua) larvae. The main focus was on proteins connected to immune function, growth and development. The results demonstrated that none of the identified cod larvae proteins showing up-regulation after administration of probiotic bacteria are known to have a function in immunity. In contrast, several proteins exhibiting down-regulation after exposure to the probiotic bacteria may be related to stress and immune responses. This indicates that the probiotic treated larvae were experiencing a lower level of immune-stimulation than the control group. It is therefore tempting to postulate that the probiotic bacteria mixture used in the present study reduced the environmental stress by inhibiting the growth of pathogenic bacteria. Most of the identified up-regulated proteins in the probiotic group relative to the control may be linked to growth and development. The most pronounced up-regulation of proteins was found in several muscle α-actin isoforms indicating improved growth upon probiotic bacteria treatment.