Pili mediated DNA exchange in the third domain of life

DNA的种间和种内转移在胁迫条件下的生存、通过水平基因转移获得新的性状和致病等过程中起着至关重要的作用。不同的生物体已经进化出各种机制来将DNA转移到其他细胞或环境中，或者吸收DNA。嗜热性古细菌Sulfolobus acidocardarius具有独特的菌毛系统，该系统由紫外线诱导，随后参与聚集的Sulfolobus细胞之间的DNA交换。这个项目将使用生化和遗传学方法来阐明菌毛组装的机制，其他Sulfolobus细胞的感知和自我聚集的启动。缺失突变分析将确定哪些蛋白质对受体或供体细胞的菌毛组装和识别至关重要。一旦确定了菌毛中的受体，就会确定触发聚集、表面附着和启动DNA转移的信号的成分(S)。菌毛操纵子下游的一组基因可能参与了交换的DNA进入Sulfolobus染色体的同源重组。这些基因的缺失突变株将用于接合分析，以表明它们参与了紫外光诱导的DNA修复。最后，我们旨在阐明紫外线诱导的菌毛如何通过同源重组参与细胞聚集、DNA交换和DNA修复的机制。

Inter- and intra species transfer of DNA plays a vital role in processes like survival under stress conditions, acquiring new traits by horizontal gene transfer and pathogenesis. Different organisms have evolved a variety of mechanisms to transfer DNA to other cells or the environment or take up DNA. The thermoacidophilic archaeon Sulfolobus acidocaldarius possesses a unique pilus system that is induced by treatment with UV light and is subsequently involved in DNA exchange between aggregated Sulfolobus cells. This project will employ biochemical and genetic methods to elucidate the mechanism of pilus assembly, sensing of other Sulfolobus cells and initiation of auto-aggregation. Deletion mutant analysis will determine which proteins are important for pilus assembly and recognition of acceptor or donor cells. Once the receptor in the pilus is identified, the component(s) will be identified which triggers the signal for aggregation, surface attachment and initiation of DNA transfer. A set of genes downstream of the pili operon might be involved in homologous recombination of exchanged DNA into the Sulfolobus chromosome. Deletion mutant strains of these genes will be used in conjugation assays to show their involvement in UV light induced DNA repair. At the end of this project we aim to elucidate the mechanism how the UV induced pili are involved in cell aggregation, DNA exchange and DNA repair by homologous recombination.