Bacterially driven anaerobic sulfide oxidation by manganese oxide reduction studied in Sulfurimonas spp. (ANAMARE)

氧化锰氧化厌氧硫化物的氧化还原反应曾多次被认为是细菌的一种可能的能源，但所有早期试图利用这种特殊代谢来丰富微生物的尝试都以失败告终。在本项目中，我们打算研究一种新分离的细菌菌株，它以硫化物或硫代硫酸盐为电子供体，以氧化锰(IV)为唯一电子受体，进行岩石自养生长。该分离物起源于黑海中部的亚缺氧带，属于硫磺单胞菌属。该属已知富含海洋氧化还原跃层，但所有较早获得的菌株都将厌氧硫化物氧化与反硝化作用结合在一起。最初的实验表明，由新菌株进行的细菌介导的硫化物和氧化锰之间的反应至少比化学反应快3-5倍。在这个项目的过程中，我们计划深入研究新菌株的生长特性，例如生长速度、生长效率和中间体如Mn(III)和S0在介质中的积累。更进一步，我们想要获得所有必要的信息，这些信息对于理解这个物种的自生学和定义它的生态位是必要的。这将包括对替代电子供体和受体的使用、有机碳源的使用、固氮、运动性和pH、盐度和温度方面的最佳生长条件等方面的研究。有了这些信息，我们的目标是有效地描述新的菌株，并将其保存在德国的培养库中。最后，我们计划对该菌株的基因组进行测序，并与其他3种硫磺单胞菌进行比较基因组和生理研究，这些研究既有纯培养，也有完整的基因组序列。因此，我们可以初步了解这种新的厌氧硫化物氧化在硫磺单胞菌中的分布范围，最重要的是，我们可以寻找参与这种新陈代谢的指示性基因。结合实验工作，基因组分析将集中在不溶性氧化锰作为电子受体的方式上。

The redox reaction of anaerobic sulfide oxidation by manganese oxide reduction has been repeatedly suggested as a possible energy source for bacteria, but all earlier attempts to enrich for microorganisms with this particular metabolism failed. In this project we propose to study a newly isolated bacterial strain, which is growing lithoautotrophically with sulfide or thiosulfate as electron donor and manganese(IV) oxide as sole electron acceptor. The isolate originates from the suboxic zone of the central Black Sea and belongs to the genus Sulfurimonas. This genus is known to be abundant in marine redoxclines, but all strains obtained earlier couple anaerobic sulfide oxidation with denitrification. First experiments revealed, that the bacterial mediated reaction between sulfide and manganese oxide, carried out by the new strain, is at least 3-5 times faster than the chemical reaction. In the course of this project, we plan to characterize the growth of the new strain in depth e.g. in terms of growth rate, growth efficiency and accumulation of intermediates such as Mn(III) and S0 in the medium. Further on, we want to gain all information, which is necessary to understand the autecology of this species and define it's ecological niche. This will include e.g. studies addressing the use of alternative electron donors and acceptors, the use of organic carbon sources, nitrogen fixation, motility and optimal growth conditions in terms of pH, salinity and temperature. With this information we aim to validly describe the new strain and deposit it in the German culture collection. Last not least we plan to sequence the genome of the strain and conduct a comparative genomic and physiological study with 3 other Sulfurimonas spp., for which both a pure culture and the complete genome sequences are available. Thereby, we can get a first impression on how wide spread this new anaerobic sulfide oxidation might be within the genus Sulfurimonas and most importantly we can search for indicative genes involved in this metabolism. In combination with experimental work, the genomic analysis will focus on the mode by which insoluble manganese oxide can be used as electron acceptor.