Members of the Shewanella genus play important roles in bioenergy generation and environmental bioremediation, but their practical applications in engineered systems are still limited due to the lack of effective synthetic biology tools and parts such as promoters and expression systems. In this work, the rhaBAD promoter of Escherichia coli was introduced into various Shewanella species including S. oneidensis MR-1, S. decolorationis S12, and S. aquimarina SW-120 to enhance their extracellular pollutant transformation ability with Cr(VI) reduction as an example. The rhaBAD promoter had low leaky expression without l-rhamnose induction and exhibited a linear response to a wide concentration range. The inducer was nontoxic and could not be metabolizable by the Shewanella species. In addition, a unimodal induction of the rhaBAD promoter was found at the single-cell level. Applying this rhamnose-inducible system to the Shewanella species allowed for precise control on their extracellular electron transfer abilities to promote Cr(VI) transformation. The engineered strain induced by l-rhamnose reduced 98% Cr(VI) within 9 h, while only 59.1% Cr(VI) reduction was achieved by the control strain. Moreover, a 3-fold higher Cr(VI) reduction rate for the engineered strain induced by l-rhamnose confirms the improvement of its biotransformation ability. Our work provides an efficient regulation tool for engineering Shewanella species and may hopefully bring them a step further toward practical applications.

中文翻译：

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工程鼠李糖诱导系统，以提高希瓦氏菌属的细胞外电子转移能力，以改善Cr（VI）还原。

希瓦氏菌属的成员在生物能产生和环境生物修复中起着重要作用，但由于缺乏有效的合成生物学工具和部件（如启动子和表达系统），它们在工程系统中的实际应用仍然受到限制。在这项工作中，将大肠杆菌的rhaBAD启动子引入了多种希瓦氏菌物种中，包括沙门氏菌MR-1，脱色链球菌S12和海带链球菌SW-120，以通过减少Cr（VI）来增强它们的细胞外污染物转化能力。一个例子。的rhaBAD启动子具有低渗漏表达没有升-鼠李糖诱导并在宽浓度范围内表现出线性响应。该诱导剂是无毒的，不能被希瓦氏菌属物种代谢。此外，在单细胞水平上发现了rhaBAD启动子的单峰诱导。将这种鼠李糖诱导系统应用于希瓦氏菌物种允许精确控制其胞外电子转移能力，以促进Cr（VI）转化。1-鼠李糖诱导的工程菌株在9 h内还原了98％的Cr（VI），而对照菌株仅还原了59.1％的Cr（VI）。此外，由l诱导的工程菌株的Cr（VI）还原速率高3倍-鼠李糖证实其生物转化能力的提高。我们的工作为设计希瓦氏菌物种提供了一种有效的调节工具，并有望使它们更进一步地走向实际应用。