There is a constant research into new feed substitutes in
the aquaculture industry in order to find solutions for diseases caused by
microbes, and the rapid development of antibiotic resistance makes it
challenging to find new substances to control the health of a stock. Many
marine bacteria produce active metabolites that represent new promising sources
for antimicrobial compounds, and species of the genera Pseudoalteromonas, Phaeobacter, Ruegeria and Vibrio are in particular of interest for sources of probiotics in
aquaculture. However, there is a lack of understanding how the bioactive
compounds could affect the eukaryotic host organisms, and the toxicity to the
animals needs to be assessed before they can be considered as useful treatments
and feed substitutes.
This study has examined the effects of bacteria and their
bioactive compounds (see Table) on two model organisms – Artemia sp. and Caenorhabditis
elegans. The authors analysed examined several bacterial strains, among
which were V. coralliilyticus and E. coli that were used as positive and
negative killing control (respectively). Live bacterial cultures were added to Artemia nauplii and C. elegans, and only Artemia
nauplii were exposed to the pure compounds additionally. Results showed that on
or both model organisms showed reduced survival in the presence of strains from
Pseudoalteromonas sp., species of the
families Photobacteriaceaea and Vibrionaceaea and of the class Actinobacter, however in contrast, the
bacterial strains of the Roseobacter clade,
producing broad-spectrum antibiotics TDA, generally had no negative effect on
the organisms, which confirms their suitability as sources for probiotics in
aquaculture.
In my opinion, this study contributed to better
understanding of the different antimicrobial compounds produced by bacteria and
their effects on eukaryotic organisms. The authors assessed the effects of
different compounds produced by different strains very neatly, and the results
give very important insights into the toxicity of the compounds on model
organisms. The crustacean tested here could be an important indicator for the
effects of the compounds on other commercially important crustacean farmed in
the aquaculture industry. However, since some differences between the nematode
and the crustaceans were found, it would be important to assess the influences
of these compounds to other farmed animals in different taxonomic groups such
as fish or shellfish before using these antimicrobial compounds safely. Moreover,
studies should be conducted to test the interactions of the strains with the
host organisms in general, so that the metabolites could be identified as the
cause of death with a higher certainty.
Neu et al. (2014). Toxicity of Bioactive and Probiotic Marine
Bacteria and Their Secondary Metabolites in Artemia
sp. and Caenorhabditis elegans as
Eukaryotic Model Organisms. Applied and Environmental Microbiology , Vol. 80(1), pp. 146-153
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