Metabolic adaptation of Acinetobacter baumannii - the cellular response to desiccation

这是导致A.鲍曼不动杆菌在卫生保健机构中的最大优势是其耐受干燥和在没有营养的情况下存活沿着时间的能力。然而，介导长期存活和抗干燥性的分子因素在很大程度上是未知的。我们通过种植A来模拟低水环境。鲍曼不动杆菌在高盐培养基中的生长，并发现其合成谷氨酸、甘露醇和海藻糖作为响应于低水活度的相容溶质。甘氨酸甜菜碱是另一种使用的相容溶质;它可以从环境中吸收或由胆碱合成。已确定了溶质形成的生物合成途径、关键酶和编码基因。我们将在此基础上进一步阐明溶质在A.鲍曼不动杆菌。第一个重点是溶质形成的调节，特别是在宿主的背景下，以及它们在毒力中的作用。为此，我们将使用报告基因检测来寻找触发溶质形成的环境信号。甘露醇生物合成中的关键酶甘露醇-1-磷酸脱氢酶/磷酸酶被盐激活的生物化学和分子基础将被揭开。海藻糖在感染和持久性中起着重要作用。海藻糖合成的突变缺陷不再能够杀死G。在高温（45°C）下生长。海藻糖这种显著作用的分子基础仍然难以捉摸。此外，我们将讨论甘露醇在毒力中的作用。第二个重点是溶质在保护免受各种压力，长期生存和干燥中的作用。待检测的强制降解条件将模拟宿主，包括pH值、氧化强制降解和温度。已经建立了在规定条件下研究干燥的实验装置，并将用于研究外源性和内源性溶质对野生型和突变株干燥的影响。另一个重要的问题是干燥本身是否会引发溶质的合成。我们做了令人惊讶的观察，溶质甘露醇和谷氨酸从细胞中消失，在后期稳定期。这可能暗示在营养缺乏的条件下溶质作为碳源和能源的再利用，并且可能暗示产生有活力但不可培养的细胞。这一假设将通过生理学实验来解决。总之，我们的目标是了解溶质在A.以确定新的目标，以打击新出现的病原体。

An important factor that contributes to the spread of A. baumannii in health care institutions is its ability to withstand desiccation and survive for along time without nutrients. However, the molecular factors that mediate long-term survival and desiccation resistance are largely unknown. We have mimicked low water environments by growing A. baumannii in high salt media and found that it synthesizes glutamate, mannitol and trehalose as compatible solutes in response to low water activities. Glycine betaine is another compatible solute used; it may be taken up from the environment or synthesized from choline taken up. The biosynthetic pathways for solute formation, the key enzymes and the encoding genes have been identified. We will build on this foundation to unravel the role of solutes in the pathobiology of A. baumannii. The first focus is on regulation of solute formation, especially in the context of the host, and their role in virulence. To this end, we will use reporter gene assays to search for environmental signals that trigger solute formation. The biochemical and molecular basis of the activation of the key enzyme in mannitol biosynthesis, the mannitol-1-phosphate dehydrogenase/phosphatase, by salt will be unravelled. It emerges that trehalose plays a prominent role in infection and persistence. A mutant defect in trehalose synthesis is no longer able to kill G. mellonella and to grow at high temperatures (45°C). The molecular basis for this pronounced role of trehalose remains elusive. Furthermore, we will address the role of mannitol in virulence. A second focus is on the role of solutes in protection against various stresses, in long-term survival and desiccation. Stress conditions to be tested will mimic the host and include pH, oxidative stress and temperature. An experimental setup to study desiccation under defined conditions has been established and will be used to study the effect of exogeneous and endogeneous solutes on desiccation using wild type as well as mutant strains. Another important question is whether desiccation itself triggers the synthesis of solutes. We made the astonishing observation that the solutes mannitol and glutamate disappear from the cells during late stationary phase. This could hint to a re-utilization of solutes as carbon and energy source under nutrient-deprived conditions and could hint to the production of viable but non-culturable cells. This hypothesis will be addressed by physiological experiments. In summary, the goal is to understand the underlying molecular basis of the role of solutes in A. baumannii to identify new targets to combat the emerging pathogen.