Use of Natural Antimicrobial Peptides and Bacterial Biopolymers for Cultured Pearl Production.

Christelle Simon-Colin,Achraf Kouzayha,Nicolas Gayet,Yannick Gueguen,Jean Guezennec,Denis Saulnier,Evelyne Bachere

doi:10.3390/md13063732

Abstract

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.

Highlights

The Tahiti pearl farming industry plays a major socio-economic role in French Polynesia
The aim of this study was to evaluate the combination of tachyplesin, a marine antimicrobial peptide (AMP) with two bacterial exopolysaccharides as an alternative route to synthetic antibiotics used for cultured pearls
The filming properties of exopolysaccharides depends on many parameters including their chemistry and the chemistry of the environment as well

Summary

Introduction

The Tahiti pearl farming industry plays a major socio-economic role in French Polynesia. Cultured pearls are the product of grafting and rearing of Pinctada margaritifera pearl oysters in their natural environment. The pearl oysters are collected and raised to serve either as donor or receiver. The grafting process takes place following a surgical operation during which the graft, a small piece of mantle tissue, is inserted into the “pearl pocket” of the receiving oyster together with a nacre bead, the nucleus. Once inserted into the receiving oyster, the external epithelial-cells of the graft multiply to form a pearl sac around the nucleus [1]. The pearl sac starts to deposit calcium carbonate polymorphs layers onto the nucleus. This is the starting point for the future pearl [2]

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