The response of anoxygenic photosynthetic bacteria to singlet oxygen

当光、氧和叶绿素同时存在时，光合生物产生单线态氧。关于细菌对单线态氧的防御机制及其调控知之甚少。我们将解开信号链背后的单线态氧反应在缺氧光合细菌。我们的初步工作的反应的facultimate光合细菌球形红细菌单线态氧揭示了两个西格玛因子蛋白质西格玛E和西格玛38的作用，并为Hfq蛋白，这是参与调节的小RNA。假定的反应调节剂OmpR表现出强烈的单线态氧的存在下，合成速率增加。σ 38缺失突变体不仅对单线态氧更敏感，而且在液体培养中显示出细胞的强聚集，表明细胞包膜的组成改变。因此，我们的调查重点将放在：1。在sigma E和sigma 38依赖性途径中的信号传导机制，2.小分子RNA的作用，3。OmpR蛋白的作用和4.单线态氧对膜蛋白的影响。一些比较研究将解决单重态氧反应在Roseobacteriumficans，这不同于R。sphaeroides即使在高氧张力下也表达光合作用基因。一个长期的目标是确定的机制，传感单线态氧。

Photosynthetic organisms generate singlet oxygen when light, oxygen and chlorophyll are simultaneously present. Little is known about bacterial defence mechanisms against singlet oxygen and their regulation. We will unravel the signal chains underlying the singlet oxygen response in anoxygenic photosynthetic bacteria. Our preliminary work on the response of the facultatively photosynthetic bacterium Rhodobacter sphaeroides to singlet oxygen revealed a role for the two sigma factor proteins sigma E and sigma 38, and for the Hfq protein, which is involved in regulation by small RNAs. The putative response regulator OmpR showed strongly increased synthesis rate in the presence of singlet oxygen. A sigma 38 deletion mutant is not only more sensitive to singlet oxygen but also shows strong aggregation of cells in liquid culture suggesting an altered composition of the cell envelope. Therefore the focus of our investigations will be on: 1. the signalling mechanisms in the sigma E and the sigma 38 dependent pathways, 2. the role of small regulatory RNAs, 3. the role of the OmpR protein and 4. the effect of singlet oxygen on membrane proteins. Some comparative studies will address the singlet oxygen response in Roseobacter denitrificans, which unlike R. sphaeroides expresses photosynthesis genes even at high oxygen tension. A long term goal is the identification of the mechanisms of sensing singlet oxygen.