Genetic modules for sensing and detoxification of novel antibacterial compounds

革兰氏阳性菌单核细胞增生性李斯特菌是李斯特菌病的病原体。李斯特菌病是一种高死亡率的人类传染病，通过食用受污染的食物而感染。单核细胞增多性乳杆菌普遍存在于土壤、地表水、植物表面或动物的肠道中。由于这种广泛发生的情况，这种细菌经常进入食物链，并经常导致大规模疾病暴发，导致许多人死亡。不同的基因及其精确的表达有助于单核细胞增多性李斯特菌在人体外的自然栖息地或在人类感染期间存活。单核细胞增多性李斯特菌的许多毒力因子是已知的，在许多情况下，它们的调控是众所周知的。相比之下，有关导致单核细胞增多性李斯特菌在环境中存活的基因的信息较少。然而，对确保这种病原体在其自然栖息地生存的分子机制的进一步了解，可能有助于减少未来由单核细胞增多性李氏杆菌污染食物的风险。序列分析显示，目前在单核细胞增多性李氏杆菌基因组中存在23个尚未确定的多药耐药(MDR)ABC转运蛋白。这些转运蛋白被认为是为了促进有毒化合物从细菌细胞中输出。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生产的抗生素，可能是为了抑制竞争物种的生长而合成的。本项目提案应对迄今未研究的23个耐多药转运蛋白及其功能进行调查。为此，应该筛选一个天然化合物文库，以鉴定对该文库中的选定化合物具有抗性的MDR转运体和/或鉴定其表达由其中一些化合物诱导的MDR转运体。在该项目的第二部分，应利用遗传和生化方法以及蛋白质结晶学的方法研究LieAB和其他相关蛋白质对金霉素A的传感和解毒机制。预期的结果将有助于我们更好地了解单核细胞增多性李氏杆菌在其自然环境中的生态相互作用，并有助于更好地确定这种重要的人类病原体的储存库。

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.