Mechanisms of heme homeostasis in Chromobacterium violaceum

• Grant number: 20/15268-2
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: August 01, 2022
• End date: September 30, 2024
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: José Freire da Silva Neto
• Grantee: Vinicius Marques de Lima
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated research grant: 21/06894-0 - Bacterial transcription factors involved in metal homeostasis, oxidative stress and virulence: investigating how Chromobacterium violaceum switches from the environment to the host, AP.JP2

Abstract

The prosthetic group heme is abundant in host's hemoproteins and explored as an iron source by many bacterial pathogens. However, heme is highly reactive, may cause damage and must be maintained in homeostasis to avoid its toxicity. In this work we intend to identify the high heme resistance mechanisms of Chromobacterium violaceum, a Gram-negative bacterium that causes severe opportunistic diseases in humans. The unbiased identification of genes involved in heme tolerance will be performed by screening of a transposon-mutant library under high heme concentration. The analysis of C. violaceum transcriptome, by RNA-seq in different heme concentrations, will be performed to identify the adaptive responses and regulatory systems that maintain heme homeostasis. The transposon and null mutants will be characterized regarding their sensitivity to heme and other agents that generate reactive oxygen species. Purified proteins will be evaluated by in vitro biochemical assays for their ability to interact with heme and have their role in heme tolerance determined. We will also investigate how ChuP exerts its regulatory role and if this protein has a more general role in heme homeostasis. The role of heme responsive genes in C. violaceum pathogenicity will be verified in vivo by mouse virulence assays. The data obtained in this work will reveal the mechanisms of heme homeostasis and its relationship with C. violaceum virulence, helping to understand why Gram-negative bacteria tolerate high levels of heme. (AU)