"Jamming the radar"

Over the last two decades aquaculture has become the fastest growth sector of agribusiness worldwide. However, aquafarming is facing one fundamental problem: Diseases. The aquaculture industry loses billions each year because of diseases caused mainly by microbial infection. In order to counter this dilemma the use of antibiotics has been widespread. Their excessive use has generated unwanted side effects. Therefore, an alternative solution is necessary. One potential solution could be quorum quenching (QQ). Many species of bacteria use quorum sensing (QS) to regulate their gene expression in response to cell-population density. Behaviors such as virulence controlled by QS only occur at high bacterial cell densities. Bacteria use autoinducers like N-acyl-homoserine lactone (AHL) for intraspecific communication. QQ enzymes which interfere with the QS system by degrading signal molecules can shut down the expression of pathogenic genes.

Recent studies have shown that there are quite a few marine bacteria with the enzymatic potential of QQ. Zheng et al. (2016) conducted a study with focus on the Pacific white shrimp (Litopenaeus vannamei). The main focus of this study was to compare the bacterial composition of different health statuses. Further, they looked at the bacterial composition of distinct larval stages. 240 bacterial strains where identified in total with a significant shift between samples from healthy and diseased populations and also within different growth stages.

What I found most interesting was that they screened the 143 strains which they isolated from healthy shrimp and water samples for their AHL degrading activity. 18 out of 143 strains showed reduction of the normalized β-galactosidase activity. The AHL level is proportional to β-galactosidase activity. Ten out of 18 strains showed strong AHL degrading potential. The dominant species with strong degrading potential were Tenacibaculum mesophilum (nine strains) and Microbacterium aquimaris (two strains). They suggest that the identified bacteria with strong degrading potential could potentially be test to control diseases in aquaculture.

In my opinion these findings are very promising. Previous studies have revealed that the use of organisms with the potential of QQ can be an effective way to block QS systems of bacteria. E.g. QQ can be used to control biofilm formation and therefore prevent biofouling (Joint et al. 2007). Additionally, the author mentioned recent studies where QQ was successfully applied to marine organisms such as the giant freshwater prawn. Anyway, further research is necessary. More bacteria with QQ potential for other farmed species have to be identified. Further, the efficiency in commercial aquaculture has yet to be proven.

If you are interested in that topic: I found two useful reviews about QQ enzymes and QQ marine agents:

Tang et al. (2014), Quorum Quenching Agents: Resources for Antivirulence Therapy, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4071575/

Chen et al. (2013), Quorum Quenching Enzymes and Their Application in Degrading Signal Molecules to Block Quorum Sensing-Dependent Infection, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3794736/

And here’s the reference for this article:

Zheng Y., Yu M., Liu Y., Su Y., Xu T., Yu M., Zhang X. (2016) Comparison of cultivable bacterial communities associated with Pacific white shrimp (Litopenaeus vannamei) larvae at different health statuses and growth stages, Aquaculture,doi:10.1016/j.aquaculture.2015.09.020

http://www.sciencedirect.com/science/article/pii/S0044848615301794