Regulation of metal uptake by TonB-dependent outer membrane transporters of the filamentous cyanobacterium Anabaena sp. PCC 7120

蓝藻主要依赖于金属。光合作用和固氮对铁等金属的需求代表了蓝细菌的挑战，因为铁一方面不容易生物利用，另一方面由于铁催化形成有毒的活性氧物质而具有危险性。蓝藻已经开发出一个控制铁吸收的调节网络来克服这种困境。在鱼腥藻PCC 7120（一种丝状蓝藻模型系统）中，已经鉴定了22种TonB依赖的外膜转运蛋白和4种TonB蛋白。此外，鱼腥藻基因组编码三个ExB和五个质膜定位运输系统。我们的结果清楚地表明了不同基因在不同条件下的特异性表达谱。此外，我们还描述了依赖于阿托伐他汀的铁摄取的复杂系统。下一步是研究一般的金属吸收的调控网络，以了解鱼腥藻PCC 7120的金属稳态和外膜蛋白在这一途径中的调控功能。这将包括TonB依赖性外膜转运蛋白的功能的描述以及TonB蛋白和ExB系统的功能和调节多样性的描述。

Cyanobacteria are majorly dependent on metals. The demand for metals like iron for photosynthesis and nitrogen fixation represents a challenge for cyanobacteria, as iron is, on the one hand, not readily bioavailable and, on the other hand, dangerous due to the iron-catalyzed formation of toxic reactiveoxygen species. Cyanobacteria have developed a regulatory network controlling the iron uptake to overcome this dilemma. In Anabaena sp. PCC 7120, a filamentous cyanobacterial model system, 22 TonB-dependent outer membrane transporters and four TonB proteins have been identified. In addition, three ExB and five plasma membrane localized transport systems are encoded by the genome of Anabaena. Our results clearly demonstrate specific expression profiles for the different genes under various conditions. In addition, we have described the complex system for the schizokinen-dependent iron uptake. The next step is to study the regulatory network for metal uptake in general to understand the metal homeostasis in Anabaena sp. PCC 7120 and the regulatory function of outer membrane proteins in this pathway. This will include the description of the function of the TonB-dependent outer membrane transporters as well as the description of the functional and regulatory diversity of the TonB proteins and ExB systems.