Abstract：
Microbial reduction of ferrihydrite is prevalent in natural environments and plays an important role in reductive dissolution of Fe(III) minerals. With consistent release of anthropogenic graphene oxide (GO) into water bodies, new changes in the Fe(III)-reducing microorganisms/ferrihydrite binary system demand attention. Herein, we focused on the interaction of GO and bacterial cells in view of colloidal stability and interfacial forces, and on the consequences for microbial ferrihydrite reduction. The results showed that the addition of GO decreased the bioreduction efficiency of ferrihydrite down to 1/15 of the control. Meanwhile, the GO nanosheets were found not depositing on ferrihydrite but spontaneously aggregating with Shewanella spp., the representative dissimilatory Fe(III) reduction bacterial species. Using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and atomic force microscopy (AFM), the aggregation process can be interpreted in three steps according to the interaction energy calculation, namely, colloidal instability, reversible aggregation and irreversible aggregation. The motility of living cells seems the reason inducing the colloidal instability between GO and bacteria. While, the aggregation remains reversible even the secondary minimum achieved at the separation distance of 8.74-9.24 nm from XDLVO. When the separation distance <5.74-6.01 nm, the adhesion work predominates and causes irreversible aggregation, validated by AFM. Additionally, the probable ecological risks raised by this aggregation behavior for the imbalance of iron biogeochemical cycle were demonstrated.
摘要：
水铁矿的微生物还原在自然环境中普遍存在，在Fe（III）矿物的还原溶解中起着重要作用。随着人为氧化石墨烯（GO）持续释放到水体中，铁（III）还原微生物/水铁矿二元体系的新变化需要关注。在这里，鉴于胶体稳定性和界面力，我们专注于GO和细菌细胞的相互作用，以及微生物水铁矿还原的后果。结果表明，添加GO可使水铁矿的生物还原效率降低至对照的1/15。同时,发现GO纳米片没有沉积在水铁矿上，而是与Shewanellaspp自发聚集。,代表性的异化Fe（III）还原细菌物种。使用扩展的Derjaguin-Landau-Verwey-Overbeek（XDLVO）理论和原子力显微镜（AFM），根据相互作用能计算，聚集过程可以分为三个步骤进行解释，即,胶体不稳定性，可逆聚集和不可逆聚集。活细胞的运动性似乎是诱导GO和细菌之间胶体不稳定的原因。同时,即使在距XDLVO8.74-9.24nm的分离距离处达到次要最小值，聚集也保持可逆。当分离距离<5.74-6.01nm时,粘附功占主导地位，并导致不可逆的聚集，经AFM验证。此外,证明了这种聚集行为对铁生物地球化学循环失衡可能带来的生态风险。
