Effect of N-acyl homoserine lactone-degrading enrichment cultures on Macrobrachium rosenbergii larviculture

Abstract

N-acyl homoserine lactone molecules (AHL) are quorum sensing molecules known to be involved in the production of virulence factors. In this study, N-acyl homoserine lactone (AHL)-degrading enrichment cultures (ECs) as bio-control agent in prawn larviculture was investigated. Enrichment cultures EC5(D) and EC5(L), originating from microbial communities of the fish gut of Dicentrarchus labrax L. and Lates calcarifer, were tested in the larval rearing of Macrobrachium rosenbergii through their addition to the rearing water and by bio-encapsulation in Artemia nauplii. The ECs were grown at the expense of glycerol released in the medium by hatching Artemia. The larval stage index of AHL-exposed larvae was 4.06±0.07 in Experiment 1 and 6.18±0.10 in Experiment 2 and 5.04±0.07 and 6.50±0.08 in the control treatment, respectively. Furthermore, a distinct difference in survival between AHL-exposed larvae (37.3%±10.6 and 64.5%±2.0) versus non-exposed larvae (77.7%±5.6 and 76.8%±3.2 in Experiments 1 and 2, respectively) was observed. Both ECs were effective in improving prawn larvae survival under experimental conditions, i.e. when the survival of prawn larvae was compromised through a daily exposure to AHL molecules (1 mg l−1). Through the addition of ECs, the negative effect of AHL could be counteracted, especially obtaining better larval quality, indicated by ammonia tolerance. These experiments demonstrated that AHL at a concentration of 1 mg l−1 could have a negative effect on prawn larvae, presumably through their effect on the prevailing opportunistic pathogenic microorganisms, while the selected ECs can counteract this. For this reason, using N-acyl homoserine lactone-degrading microbial communities might be a useful tool in prawn larviculture.