Atlantic cod are a popular fish that are often available from most fish and chip shops. In recent years the quantity of species caught from wild populations has decreased, not only has the quantity reduced but so has the size as the catch records have shown, this is because they are a slow growing species and have not had the time to grow to their full potential.
In this paper the authors investigate nearly 500 probiont candidates, and used two screening types to whittle them down to just five. The authors first isolated bacteria from cod larvae which were taken from several samples within different rearing technologies, the bacteria were then brought to pure culture and characterised phenotypically. Depending on the dominance, uniqueness and fermentative ability the pool of 500 was reduced to approximately 10%. These isolates were then characterised in vitro according to adhesion to mucus, growth in mucus, production of extracellular enzymes, fish bile resistance and haemolytic properties for the second screening which then produced seven isolates. These isolates were then tested in vivo on cod larvae and two were excluded due to increased mortality of the cod larvae. The remaining five one of which was a Vibrio, two a Microbacterium and the remaining two being Ruegeria and Psuedoalteromonas increased the survival of the cod larvae compared to the positive control. The authors suggested that these screening methods were viable for the selection of making multistrain probiotics.
The wider significance of this investigation is paramount with regards to probiotic selection. Dr Merrifield in one of his lectures implied that it would be impossible to select a single probiotic to treat all symptoms exhibited by a single fish species. Selecting the best compilation of probiotics could treat all of the symptoms; therefore the screening methods used in this investigation should be applied to the selection of all probiotics although they should be tested on a range of species to see if they exhibit the same response.
A Review of: Fjellheim, A. J., Klinkenberg, G., Skjermo, J., Aasen, I. M., & Vadstein, O. (2010). Selection of candidate probionts by two different screening strategies from Atlantic cod (Gadus morhua L.) larvae. Veterinary microbiology, 144(1-2), 153-9.
4 comments:
Hi Dan
This topic is very interesting but at the same time it seems so complicated as the communities are so complex. Just out of interest, the two species they excluded due to increased mortality, did the authors say what species they were? I guess they might have been pathogens rather than 'friendly' bacteria from the gut.
Lee
Hi Lee,
Sorry buddy, the authors just refer to them as probiotic candidates, I also made the assumption that they were pathogens. unfortunately we won't know!
Hey Dan,
did the authors mention any kind of limitation to this screening process, such as time or cost, that would prevent it from being applied to a large number of commercially important species? if not then maybe this could be really helpfull in the aquaculture industry!!
Hey Nikie,
Unfortunately they did not, but from my experience a method which involves culture techniques is very time consuming which for an industrial application will be expensive. The choice is if the outcome will then cover the costs of investigations and production of said probiotics. sorry I could not be of more help.
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