培养条件对Shewanella oneidensis MR-1电极生物膜及细胞形貌的影响

Impact of culture conditions on the biofilm and cell morphology of Shewanella oneidensis MR-1

摘要:

【目的】 Shewanella oneidensis MR-1是电活性模式微生物，但目前仍缺乏对其细胞及生物膜形貌变化的系统研究，本研究旨在完善对其形貌特征的理解，为支持其作为模式微生物提供有力的基础数据。【方法】选取培养基类型、缓冲液浓度、维生素、微量元素、无机盐、电子穿梭体、电子供体、电子受体等培养条件作为变量，采用恒电位培养法获得生物膜，通过扫描电子显微镜对生物膜形貌进行观察。【结果】低浓度缓冲液中(30 mmol/L和100 mmol/L)，其细胞多为短杆状，高浓度缓冲液中(200 mmol/L和300 mmol/L)细胞卷曲伸长；缺乏维生素、微量元素、无机盐则可使生物膜紧贴电极生长，变得致密；而穿梭体和电子受体对于S.oneidensis MR-1极为关键，前者的存在可显著促进生物膜的厚度，后者的缺失可迫使生物膜细胞裂解；此外，通过形貌研究发现，S.oneidensis MR-1可首尾相连形成超过100 μm的长线状结构。【结论】可通过改变缓冲液浓度、培养基类型、电子穿梭体和电子供受体等变量，实现Shewanella oneidensis MR-1电极生物膜及细胞形貌的调控。

Abstract:

[Objective] Although Shewanella oneidensis MR-1 is a typical electroactive model bacterium, its biofilm morphology remains to be systematically studied. This work aims to improve the understanding of biofilm morphology of S. oneidensis MR-1, thus providing basic data to support its role as a model strain. [Methods] Culture conditions such as medium type, buffer concentration, vitamins, trace elements, inorganic salts, electron shuttles, donors, and acceptors were taken as the variables to be studied. The biofilm was cultured under potentiostatic conditions and examined by scanning electron microscopy. [Results] The cells were mostly straight and short in low-concentration (30 mmol/L and 100 mmol/L) buffer solutions while became curled and elongated in high-concentration (200 mmol/L and 300 mmol/L) buffer solutions. The shortage of vitamins, trace elements, and inorganic salts made the biofilm become compact and attach closely to the electrode. The addition of an electron shuttle substantially thickened the biofilm, while a lack of an electron acceptor led to serious cell lysis within one day. In addition, a cable-like structure as long as 100 μm was observed in the biofilm, which indicated a long-distance electron transfer survival strategy of S. oneidensis MR-1. [Conclusion] Changing the medium type, buffer concentration, electron shuttles, donors, and acceptors can regulate the biofilm and cell morphology of S. oneidensis MR-1.