Functional studies of the Chromobacterium violaceum type VI secretion system

• Grant number: 18/03979-1
• Support type: Scholarships in Brazil - Doctorate (Direct)
• Effective date (Start): September 01, 2018
• Effective date (End): January 31, 2023
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal researcher: José Freire da Silva Neto
• Grantee: Júlia Aparecida Alves
• Home Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Secretion systems are specialized nanomachines present in several Gram-negative bacteria, responsible for protein translocation from the bacterial cytoplasm to the extracellular milieu. The Type VI secretion system (T6SS) is a contractile apparatus that delivery toxic protein effectors in a contact dependent manner directly into eukaryotic or prokaryotic target cells. Bacteria use this system mainly in antagonistic relationships against other competitor bacteria or eukaryotic host cells. Chromobacterium violaceum, a free-living beta-proteobacterium able to act as an opportunistic pathogen in humans, has a gene cluster in its genome organized in two operons that encodes a potential T6SS, whose function still completely unknown in this organism. This project aims to characterize the T6SS of C. violaceum with goal to unveil which are its effectors, how it is regulated and which advantage this system offers to bacterial survival in the environment and during an infection. To identify protein effectors translocated by the T6SS, we will perform a proteomic analysis comparing secretome of wild type and T6SS mutant cells. In vivo and in vitro gene expression analysis of the T6SS operons, using different conditions, will allow understand their regulation in transcriptional level. In addition, we will perform virulence assays using cell culture and a murine model, and interbacterial competition assays, with the wild type and T6SS mutant strains. Together, the results obtained will allow to understanding the role of the T6SS in the C. violaceum relationships with other bacteria and the host. (AU)