Some microorganisms can respire with extracellular electron acceptors using an extended electron transport chain to the cell surface. This process can be applied in bioelectrochemical systems in which the organisms produce an electrical current by respiring with an anode as electron acceptor. These organisms apply flavin molecules as cofactors to facilitate one-electron transfer catalyzed by the terminal reductases and in some cases as endogenous electron shuttles. In the model organism Shewanella oneidensis, riboflavin production and excretion trigger a specific biofilm formation response that is initiated at a specific threshold concentration, similar to canonical quorum-sensing molecules. Riboflavin-mediated messaging is based on the overexpression of the gene encoding the putrescine decarboxylase speC which leads to posttranscriptional overproduction of proteins involved in biofilm formation. Using a model of growth-dependent riboflavin production under batch and biofilm growth conditions, the number of cells necessary to produce the threshold concentration per time was deduced. Furthermore, our results indicate that specific retention of riboflavin in the biofilm matrix leads to localized concentrations, which by far exceed the necessary threshold value. This study describes a new quorum-sensing mechanism in S. oneidensis. Biofilm formation of S. oneidensis is induced by low concentrations of riboflavin resulting in an upregulation of the ornithine-decarboxylase speC. The results can be applied for the development of strains catalyzing increased current densities in bioelectrochemical systems.

中文翻译：

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胞外核黄素诱导Shewanella oneidensis厌氧生物膜形成

一些微生物可以通过延伸到细胞表面的电子传输链与细胞外电子受体一起呼吸。该过程可应用于生物电化学系统，其中生物体通过以阳极作为电子受体进行呼吸来产生电流。这些生物体应用黄素分子作为辅助因子来促进由末端还原酶催化的单电子转移，在某些情况下作为内源性电子穿梭。在模式生物 Shewanella oneidensis 中，核黄素的产生和排泄会触发特定的生物膜形成反应，该反应在特定的阈值浓度下启动，类似于典型的群体感应分子。核黄素介导的消息传递基于编码腐胺脱羧酶 speC 的基因的过度表达，这导致参与生物膜形成的蛋白质的转录后过度产生。使用分批和生物膜生长条件下的生长依赖性核黄素生产模型，推导出每次产生阈值浓度所需的细胞数量。此外，我们的结果表明，核黄素在生物膜基质中的特定保留导致局部浓度，远远超过必要的阈值。这项研究描述了 S. oneidensis 中一种新的群体感应机制。S. oneidensis 的生物膜形成是由低浓度的核黄素诱导的，导致鸟氨酸脱羧酶 speC 的上调。