Genetic modules for sensing and detoxification of novel antibacterial compounds

革兰氏阳性菌单核细胞增生李斯特菌是病原体的弧菌病。李斯特菌病是一种通过食用受污染的食物而获得的高死亡率的人类传染病。L.单核细胞增多症普遍存在于土壤、地表水和植物表面或动物肠道中。由于这种广泛的发生，这种细菌经常进入食物链，并经常导致大规模疾病爆发，造成许多人死亡。不同的基因组合及其精确表达促进了L.单核细胞增生李斯特氏菌在人体外的自然栖息地或在人类感染过程中的许多毒力因子。单核细胞增多症是已知的，并且在许多情况下，它们的调节是众所周知的。与此相反，关于影响L.单核细胞增多症然而，提高对确保该病原体在其自然栖息地生存的分子机制的认识，可能有助于降低由L.序列分析显示，在单核细胞增生李斯特菌基因组中存在23个迄今为止尚未表征的多药耐药（MDR）ABC转运蛋白。单核细胞增多症这些转运蛋白被认为有助于将有毒化合物排出细菌细胞。我们自己对MDR转运蛋白LieAB的研究表明，天然抗菌化合物如金霉素A是这些MDR转运蛋白的底物之一。金霉素A是一种由另一种土壤细菌产生的抗生素，可能是为了抑制竞争物种的生长而合成的。23个迄今未研究的MDR转运蛋白及其功能应在本项目提案中进行研究。为此，应筛选天然化合物文库以鉴定赋予对该文库中所选化合物的抗性的MDR转运蛋白和/或鉴定其表达由这些化合物中的一些诱导的MDR转运蛋白。因此，应更详细地研究化合物传感和化合物解毒的潜在分子机制。在拟议项目的第二部分中，应使用遗传和生物化学方法以及蛋白质晶体学研究LieAB和进一步相关蛋白质对金霉素A的传感和解毒机制。预期的结果将提高我们对L.在其自然环境中的单核细胞增多症，并应有助于更好地指定这一重要的人类病原体的水库。

The Gram positive bacterium Listeria monocytogenes is the causative agent of listeriosis. Listeriosis is an infectious human disease with high mortality and acquired through the consumption of contaminated food. L. monocytogenes is ubiquitously present in the soil, in surface water and on plant surfaces or in the gut of animals. Because of this widespread occurrence, the bacterium frequently enters the food chain and regularly causes large disease outbreaks with many deaths. Different set of genes and their precise expression facilitate the survival of L. monocytogenes in its natural habitats outside the human body or during human infection.Many of the virulence factors of L. monocytogenes are known and in many cases their regulation is well-understood. In contrast, less information is available on the genes that contribute to the survival of L. monocytogenes in the environment. However, an improved knowledge on the molecular mechanisms ensuring the survival of this pathogen in its natural habitats could help to reduce the risk of food contaminations by L. monocytogenes in the future.Sequence analyses have revealed the presence of 23 so far uncharacterized multi drug resistance (MDR) ABC transporters in the genome of L. monocytogenes. These transporters are supposed to facilitate the export of toxic compounds out of the bacterial cell. Our own research on the MDR transporter LieAB demonstrated that natural antimicrobial compounds such as aurantimycin A are among the substrates of these MDR transporters. Aurantimycin A is an antibiotic produced by another soil-dwelling bacterium and probably synthesized to inhibit the growth of competing species. The 23 so far unstudied MDR transporters and their function should be investigated in this project proposal. For this purpose, a natural compound library should be screened to identify MDR transporters conferring resistance against selected compounds in this library and/or to identify MDR transporters the expression of which is induced by some of these compounds. The underlying molecular mechanisms of compound sensing and compound detoxification should then be studied in more detail.In the second part of the proposed project, the mechanisms of sensing and detoxification of aurantimycin A by LieAB and by further associated proteins should be studied using genetic and biochemical approaches as well as protein crystallography. The expected results should improve our understanding of the ecological interactions of L. monocytogenes in its natural environment and should help to better specify the reservoir of this important human pathogen.