Global response of Chromobacterium violaceum to metal limitation mediated by the host-defense protein calprotectin

• Grant number: 23/09116-3
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: August 01, 2023
• End date: July 31, 2025
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: José Freire da Silva Neto
• Grantee: Juliano Novak
• 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 transition metals iron, zinc, and manganese are micronutrients essential to life. Vertebrate hosts restrict metal bioavailability to limit microbial growth, a process called nutritional immunity. Calprotectin (CP) is a host-defense protein released by neutrophils during infection that chelates iron, zinc, and manganese. Although the inhibitory effect of CP on bacterial growth is well-documented, the bacterial responses to CP are poorly understood. In this work, we will investigate the global transcriptional response of the opportunistic pathogen Chromobacterium violaceum to CP and characterize CP-regulated genes. We will perform RNA sequencing (RNA-seq) on C. violaceum wild-type strain untreated or treated with CP. The CP-regulated genes from the RNA-seq data will be validated by RT-qPCR, and the expression of some selected genes will be analyzed in vivo by bioluminescence reporter promoter fusions. We will select CP-regulated genes to further functional characterization, mainly those related to intracellular allocation or buffering of zinc. One of the genes that will be studied is CV3067, encoding a putative zinc metallochaperone. Null mutant strains will be obtained by allelic exchange and tested regarding susceptibility to metal limitation and attenuation of virulence in wild-type and CP knockout mice. A new mouse infection model of C. violaceum injected subcutaneous will be developed to assess the role of CP-regulated genes in abscesses. Our data should reveal the global response of a bacterial pathogen to CP, expanding the knowledge about the mechanisms of bacteria to overcome the host nutritional immunity. (AU)