Project Details
Projekt
Metabolic adaptation of Acinetobacter baumannii - the cellular response to desiccation
Applicant
Professor Dr. Volker Müller
Subject Area
Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology
Term
from 2014 to 2020
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 258351992
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.
DFG Programme
Research Units
