Plastic wastes accumulation in marine environments is becoming a crucial issue; while the toxicity to biota is quite well explored, a gap of knowledge still exists on the role that plastics play in shaping bacterial community structures in marine conditions and their possible transmission to humans. The present study intended first to profile bacterial community structure in floating plastic particles (FP) biofilms and seawater from four Tunisian coastal areas using high-throughput sequencing (HTS) of 16S rDNA. Subsequently, mussels (Mytilus galloprovincialis) as filter feeding organisms were exposed to the FP to broaden the knowledge on the potential role played by environmental plastic particles in shaping bacterial community structures and on their possibility to act as vehicles of bacteria through the food web. The mussels’ microbiota was microbiologically analyzed through HTS, and the Histidine Rich Glycoprotein (HRG) gene expression level was investigated as the main immune response. Our results clearly showed a great variation in the composition of bacterial communities of FP and seawater from different geographical areas. Moreover, the gills of mussels exposed to sterilized seawater and native FP from each site exhibited a wider bacterial biodiversity. The gene expression level of HRG was found to be significantly higher in animals exposed to native FP when compared to sterilized FP. Our results should be carefully considered in view of the Trojan horse effects of FP toward bacteria and its potential toxicity.

海洋环境中塑料废物的积累正成为一个关键问题；虽然对生物群的毒性进行了很好的探索，但关于塑料在塑造海洋条件下的细菌群落结构及其可能传播给人类的作用方面仍然存在知识空白。本研究旨在首先使用 16S rDNA 的高通量测序 (HTS) 分析突尼斯四个沿海地区的漂浮塑料颗粒 (FP) 生物膜和海水中的细菌群落结构。随后，贻贝（Mytilus galloprovincialis) 当滤食性生物暴露于 FP 时，以拓宽关于环境塑料颗粒在塑造细菌群落结构中所起的潜在作用以及它们通过食物网充当细菌载体的可能性的知识。通过 HTS 对贻贝的微生物群进行微生物学分析，并研究了富含组氨酸的糖蛋白 (HRG) 基因表达水平作为主要的免疫反应。我们的结果清楚地表明，来自不同地理区域的 FP 和海水的细菌群落组成存在很大差异。此外，暴露于消毒海水和来自每个地点的本地 FP 的贻贝的鳃表现出更广泛的细菌生物多样性。与无菌 FP 相比，暴露于天然 FP 的动物中 HRG 的基因表达水平显着更高。