Abstract：
While the multiple functions of extracellular DNA (exDNA) in biofilm formation and electron transfer have been extensively studied in pure culture, its role in mixed anodic biofilm was still unknown. In this study, we employed DNase I enzyme to digest exDNA, thereby investigating its role in anodic biofilm formation based on the performance of four microbial electrolysis cells (MECs) groups with different DNase I enzyme concentration (0, 0.05, 0.1, 0.5 mg/mL). The responding time to reach 60 % maximum current of treatment group with DNase I enzyme has been significantly reduced to 83 %-86 % of the blank group (t-test, p < 0.01), indicating the exDNA digestion could promote the biofilm formation at the early stage. The anodic coulombic efficiency was enhanced by 10.74- 54.42 % in treatment group (t-test, p < 0.05), which could be ascribed to the higher absolute abundance of exoelectrogens. The lower relative abundance of exoelectrogens indicated the DNase I enzyme addition was beneficial for the enrichment of extensive species rather than exoelectrogens. As the DNase I enzyme augments the fluorescence signal of exDNA distribution in the small molecular weight region, implying the short chain exDNA could contribute to the biomass enhancement via boosting the most species enrichment. Furthermore, the exDNA alteration improved the complexity of microbial network. Our findings provide a new insight into the role of exDNA in the extracellular matrix of anodic biofilms.
摘要：
虽然胞外DNA(exDNA)在生物膜形成和电子转移中的多种功能已经在纯培养中得到了广泛的研究,其在混合阳极生物膜中的作用尚不清楚。在这项研究中,我们用DNaseI酶消化exDNA，从而根据具有不同DNaseI酶浓度（0、0.05、0.1、0.5mg/mL）的四个微生物电解池（MECs）组的性能，研究其在阳极生物膜形成中的作用。用DNaseI酶处理组达到60%最大电流的反应时间已显著减少至空白组的83%-86%(t检验,p<0.01),表明exDNA消化可以促进早期生物膜的形成。治疗组的阳极库仑效率提高了10.74-54.42%(t检验，p<0.05)，这可以归因于外电原的绝对丰度较高。较低的相对丰度的外电原表明，添加DNaseI酶有利于富集广泛的物种，而不是外电原。由于DNaseI酶增强了小分子量区域中exDNA分布的荧光信号，暗示短链exDNA可以通过促进大多数物种的富集来促进生物量的增加。此外，exDNA的改变提高了微生物网络的复杂性。我们的发现为exDNA在阳极生物膜的细胞外基质中的作用提供了新的见解。
