Use of Natural Antimicrobial Peptides and Bacterial Biopolymers for Cultured Pearl Production
Résumé
Cultured pearls are the product of grafting and rearing of Pinctada margaritifera
pearl oysters in their natural environment. Nucleus rejections and oyster mortality appear
to result from bacterial infections or from an inappropriate grafting practice. To reduce the
impact of bacterial infections, synthetic antibiotics have been applied during the grafting
practice. However, the use of such antibiotics presents a number of problems associated
with their incomplete biodegradability, limited efficacy in some cases, and an increased
risk of selecting for antimicrobial resistant bacteria. We investigated the application of a
marine antimicrobial peptide, tachyplesin, which is present in the Japanese horseshoe crab
Tachypleus tridentatus, in combination with two marine bacterial exopolymers as alternative
treatment agents. In field studies, the combination treatment resulted in a significant
reduction in graft failures vs. untreated controls. The combination of tachyplesin (73 mg/L)
with two bacterial exopolysaccharides (0.5% w/w) acting as filming agents, reduces
graft-associated bacterial contamination. The survival data were similar to that reported for
antibiotic treatments. These data suggest that non-antibiotic treatments of pearl oysters
may provide an effective means of improving oyster survival following grafting procedures.