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Bacterial transcription factors involved in metal homeostasis, oxidative stress and virulence: investigating how Chromobacterium violaceum switches from the environment to the host


Bacteria have sophisticated mechanisms to survive in hostile environments. Bacterial pathogens must deal with harsh stress conditions inside the host, such as oxidative stress and limitation of the essential metals iron, zinc, and manganese. This project aims to unravel how the environmental opportunistic pathogen Chromobacterium violaceum coordinates adaptive responses of metal homeostasis and antioxidant defense with the expression of virulence factors to survive in the host. We will construct a transposon mutant library in C. violaceum and develop an alternative infection model using Galleria mellonella. The library will be screened in G. mellonella to discover novel C. violaceum virulence factors and on CAS plates to identify novel transcription factors involved in siderophore regulatory networks. RNA sequencing (RNA-seq) will be used to identify the C. violaceum responses to intracellular infection, metal limitation mediated by the host-defense protein calprotectin, and metal intoxication by heme and manganese. The regulons of several C. violaceum transcription factors involved with metal homeostasis, oxidative stress, and virulence will be determined by RNA-seq and ChIP-seq. Null mutant strains will be used to characterize (I) the role of transporters for the uptake or efflux of iron, heme, zinc, and manganese; (II) the role of glutathione and the GarAB system in metal and oxidative stress defense; (III) the role of the type VI secretion system (T6SS) in metal uptake; (IV) the role of transcription factors in biofilm formation and antibiotic resistance. Data obtained in this project will reveal bacterial strategies to overcome host nutritional immunity. (AU)

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