Novel approach of using homoserine lactone-degrading and poly-β-hydroxybutyrate-accumulating bacteria to protect Artemia from the pathogenic effects of Vibrio harveyi

Abstract

Homoserine lactone-degrading and poly-β-hydroxybutyrate-accumulating enrichment cultures (ECs) were obtained using glycerol as C-source and homoserine lactones as N-source, at a high C/N ratio (78). The kinetics of acyl homoserine lactone (AHL) degradation was established and the poly-β-hydroxybutyrate (PHB) content of the obtained ECs was determined. The ECs were characterised through denaturing gradient gel electrophoresis (DGGE) and the main bands were genetically identified by sequence analysis. In a Vibrio challenge test using Artemia as target organism, a distinct difference in survival of challenged Artemia between the treatments with and without the presence of ECs was observed (53% ± 6; 69% ± 5 and 58% ± 8 versus 4% ± 5; 4% ± 5 and 25% ± 21) in three independent experiments. There was a strong positive correlation between the relative percentage survival values of Artemia and the AHL degradation rate and the PHB content of the ECs. Challenge data with a quorum sensing mutant suggested that the quorum quenching ability of the ECs was less relevant in this Artemia model system, pointing to the importance of PHB. The potential of growing these beneficial ECs on glycerol released into the hatching medium of Artemia was an asset that still requires validation at hatchery level.