Abstract：
Microplastic (MP) biofilms provide a specific microniche for microbial life and are a potential hotspot for the horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs). Nevertheless, the acquisition of ARGs in MP biofilms via natural transformation mediated by extracellular DNA (eDNA) has been rarely explored. This study demonstrated that MP biofilms promoted the natural transformation of extracellular ARGs at the single-cell and multi-species levels, compared to natural substrate (NS) biofilms and bacterioplankton. The transformation frequency on MP biofilms was up to 1000-fold compare to that on NS. The small MPs and aged MPs enhanced the ARG transformation frequencies up to 77.16-fold and 32.05-fold, respectively, compared with the large MPs and pristine MPs. The transformation frequencies on MP biofilms were significantly positively correlated with the bacterial density and extracellular polymeric substance (EPS) content (P < 0.05). Furthermore, MPs significantly increased the expression of the biofilm formation related genes (motA and pgaA) and DNA uptake related genes (pilX and comA) compared to NS and bacterioplankton. The more transformants colonized on MPs contributed to the enhanced transformation frequencies at the community-wide level. Overall, eDNA-mediated transformation in MP biofilms may be an important path of ARG spread, which was promoted by heterogeneous biofilm.
摘要：
微塑料（MP）生物膜为微生物生命提供了特定的微细胞，并且是抗生素抗性基因（ARG）的水平基因转移（HGT）的潜在热点。然而，通过细胞外DNA（eDNA）介导的自然转化获得MP生物膜中的ARGs很少被探索。这项研究表明，MP生物膜在单细胞和多物种水平上促进了细胞外ARGs的自然转化。与天然底物（NS）生物膜和浮游细菌相比。与NS相比，MP生物膜上的转化频率高达1000倍。小议员和老年议员将ARG转换频率提高了77.16倍和32.05倍，分别,与大议员和原始议员相比。MP生物膜上的转化频率与细菌密度和胞外聚合物(EPS)含量呈显著正相关(P<0.05)。此外，与NS和浮游细菌相比，MPs显着增加了生物膜形成相关基因（motA和pgaA）和DNA摄取相关基因（pilX和comA）的表达。在MP上定居的转化子越多，在整个社区范围内的转化频率就越高。总的来说,eDNA介导的MP生物膜转化可能是ARG传播的重要途径，这是由异质生物膜促进的。
