Regulation of clostridial solvent production by Quorum sensing

梭状芽胞杆菌属的厌氧细菌以其将各种原料转化为工业上重要的溶剂的能力而闻名。过去，梭菌发酵被用于丙酮和丁醇的大规模生产；目前也在开发可在工业废气中生长的乙醇生成物种。低溶剂产率/滴度仍然是一个令人担忧的问题，因此，通过代谢工程来改善生物体的性能已经付出了相当大的努力。然而，尚未取得决定性的突破。造成这种情况的一个主要原因是我们对生物体的生理和代谢的理解有限，特别是对控制溶剂形成时间和程度的机制的理解有限。在之前的DTP项目中，我们在产溶剂梭菌中发现了大量的群体感应系统，它使群体中的单个细胞能够通过扩散信号分子相互通信。我们已经证明，许多这些系统强烈影响丙酮，丁醇和乙醇的生产，但潜在的分子机制尚不清楚。然而，深入了解制约溶剂形成的生理因素和调控机制是成功进行相应物种代谢工程的先决条件。利用已建立的工业菌株，本研究的具体目的是：(i)确定群体感应缺陷突变体中发生的转录，翻译和生理变化；（ii）鉴定特定群体感应调节剂直接调节的基因；（iii）利用这一知识来产生菌株，其中通过更早或更高程度地表达相关基因可以最大限度地形成溶剂

Anaerobic bacteria of the genus Clostridium are well known for their ability to convert diverse feedstocks into industrially important solvents. In the past, clostridial fermentations were used for the large scale production of acetone and butanol; nowadays ethanol-forming species are also being exploited which can grow on industrial waste gases. Low solvent yields/titres remain a concern and, thus, considerable efforts have been devoted to improving the organisms' performance through metabolic engineering. However, decisive breakthroughs are yet to be made. A major reason for this is our limited understanding of the organisms' physiology and metabolism, in particular the mechanisms that govern timing and extent of solvent formation. In previous DTP projects, we discovered a large number of quorum sensing systems in solvent-producing clostridia, which enable individual cells of a population to communicate with one another via diffusible signal molecules. We have shown that many of these systems strongly influence the production of acetone, butanol and ethanol, but the underlying molecular mechanisms remain unknown. However, a thorough understanding of the physiological factors and regulatory mechanisms constraining solvent formation is a prerequisite for successful metabolic engineering of the respective species. Using an established industrial strain, the specific aims of this study are to (i) establish the transcriptional, translational, and physiological changes occurring in quorum sensing-deficient mutants (ii) identify the genes directly regulated by specific quorum sensing regulators (iii) exploit this knowledge for the generation of strains in which solvent formation can be maximised by earlier or higher expression of the genes involved