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Promoting bidirectional extracellular electron transfer of Shewanella oneidensis MR-1 for hexavalent chromium reduction via elevating intracellular cAMP level.
Biotechnology and Bioengineering ( IF 3.5 ) Pub Date : 2020-02-18 , DOI: 10.1002/bit.27305 Zhou-Hua Cheng 1 , Jia-Rui Xiong 2 , Di Min 3 , Lei Cheng 1 , Dong-Feng Liu 3 , Wen-Wei Li 3 , Fan Jin 2 , Min Yang 4 , Han-Qing Yu 3
Biotechnology and Bioengineering ( IF 3.5 ) Pub Date : 2020-02-18 , DOI: 10.1002/bit.27305 Zhou-Hua Cheng 1 , Jia-Rui Xiong 2 , Di Min 3 , Lei Cheng 1 , Dong-Feng Liu 3 , Wen-Wei Li 3 , Fan Jin 2 , Min Yang 4 , Han-Qing Yu 3
Affiliation
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The bioreduction capacity of Cr(VI) by Shewanella is mainly governed by its bidirectional extracellular electron transfer (EET). However, the low bidirectional EET efficiency restricts its wider applications in remediation of the environments contaminated by Cr(VI). Cyclic adenosine 3',5'-monophosphate (cAMP) commonly exists in Shewanella strains and cAMP-cyclic adenosine 3',5'-monophosphate receptor protein (CRP) system regulates multiple bidirectional EET-related pathways. This inspires us to strengthen the bidirectional EET through elevating the intracellular cAMP level in Shewanella strains. In this study, an exogenous gene encoding adenylate cyclase from the soil bacterium Beggiatoa sp. PS is functionally expressed in Shewanella oneidensis MR-1 (the strain MR-1/pbPAC) and a MR-1 mutant lacking all endogenous adenylate cyclase encoding genes (the strain Δca/pbPAC). The engineered strains exhibit the enhanced bidirectional EET capacities in microbial electrochemical systems compared with their counterparts. Meanwhile, a three times more rapid reduction rate of Cr(VI) is achieved by the strain MR-1/pbPAC than the control in batch experiments. Furthermore, a higher Cr(VI) reduction efficiency is also achieved by the strain MR-1/pbPAC in the Cr(VI)-reducing biocathode experiments. Such a bidirectional enhancement is attributed to the improved production of cAMP-CRP complex, which upregulates the expression levels of the genes encoding the c-type cytochromes and flavins synthetic pathways. Specially, this strategy could be used as a broad-spectrum approach for the other Shewanella strains. Our results demonstrate that elevating the intracellular cAMP levels could be an efficient strategy to enhance the bidirectional EET of Shewanella strains and improve their pollutant transformation capacity.
中文翻译：
通过提高细胞内cAMP的水平，促进沙瓦氏假单胞菌MR-1的双向细胞外电子转移以减少六价铬。
希瓦氏菌对Cr（VI）的生物还原能力主要受其双向胞外电子转移（EET）支配。但是，双向EET效率低，限制了其在修复受Cr（VI）污染的环境中的广泛应用。希瓦氏菌菌株中普遍存在环状腺苷3'，5'-单磷酸（cAMP），而cAMP-环状腺苷3'，5'-单磷酸受体蛋白（CRP）系统调节多个双向EET相关途径。这激发了我们通过提高希瓦氏菌菌株中的细胞内cAMP水平来增强双向EET的作用。在这项研究中，来自土壤细菌Beggiatoa sp。的编码腺苷酸环化酶的外源基因。PS在功能性沙门氏菌希瓦氏菌MR-1（菌株MR-1 / pbPAC）和缺少所有内源性腺苷酸环化酶编码基因（菌株Δca/ pbPAC）的MR-1突变体中表达。与微生物菌株相比，工程菌株在微生物电化学系统中具有增强的双向EET能力。同时，在分批实验中，通过MR-1 / pbPAC菌株，Cr（VI）的快速还原速率是对照的三倍。此外，在还原Cr（VI）的生物阴极实验中，菌株MR-1 / pbPAC还实现了更高的Cr（VI）还原效率。这种双向增强归因于cAMP-CRP复合物产量的提高，该复合物上调了编码c型细胞色素和黄素合成途径的基因的表达水平。特别，该策略可以用作其他希瓦氏菌菌株的广谱方法。我们的结果表明，提高细胞内cAMP水平可能是提高Shewanella菌株双向EET和提高其污染物转化能力的有效策略。
更新日期：2020-04-09
中文翻译：
通过提高细胞内cAMP的水平，促进沙瓦氏假单胞菌MR-1的双向细胞外电子转移以减少六价铬。
希瓦氏菌对Cr（VI）的生物还原能力主要受其双向胞外电子转移（EET）支配。但是，双向EET效率低，限制了其在修复受Cr（VI）污染的环境中的广泛应用。希瓦氏菌菌株中普遍存在环状腺苷3'，5'-单磷酸（cAMP），而cAMP-环状腺苷3'，5'-单磷酸受体蛋白（CRP）系统调节多个双向EET相关途径。这激发了我们通过提高希瓦氏菌菌株中的细胞内cAMP水平来增强双向EET的作用。在这项研究中，来自土壤细菌Beggiatoa sp。的编码腺苷酸环化酶的外源基因。PS在功能性沙门氏菌希瓦氏菌MR-1（菌株MR-1 / pbPAC）和缺少所有内源性腺苷酸环化酶编码基因（菌株Δca/ pbPAC）的MR-1突变体中表达。与微生物菌株相比，工程菌株在微生物电化学系统中具有增强的双向EET能力。同时，在分批实验中，通过MR-1 / pbPAC菌株，Cr（VI）的快速还原速率是对照的三倍。此外，在还原Cr（VI）的生物阴极实验中，菌株MR-1 / pbPAC还实现了更高的Cr（VI）还原效率。这种双向增强归因于cAMP-CRP复合物产量的提高，该复合物上调了编码c型细胞色素和黄素合成途径的基因的表达水平。特别，该策略可以用作其他希瓦氏菌菌株的广谱方法。我们的结果表明，提高细胞内cAMP水平可能是提高Shewanella菌株双向EET和提高其污染物转化能力的有效策略。
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