Characterization of regulatory pathways and adhesins involved in biofilm formation and pathogenicity of Chromobacterium violaceum

• Grant number: 22/05485-1
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: October 01, 2022
• End date: February 28, 2026
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: José Freire da Silva Neto
• Grantee: Raquel Sousa Freire
• 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

RTX adhesins secreted by type I secretion systems (T1SS) and hemagglutinin adhesins secreted by type V secretion systems (T5SS) are important virulence factors of Gram-negative bacteria and act in biofilm formation and adhesion/ invasion of host cells. Chromobacterium violaceum is a Gram-negative beta-proteobacterium that causes serious infections in humans. By in silico analysis, we identified in the genome of C. violaceum, gene clusters that encode T1SSs and RTX proteins and clusters that encode T5SSs and hemagglutinin-like adhesins. Our preliminary data demonstrate that the RTX protein CV_0311 is secreted by the T1SS CV_0306-07-08 and acts on biofilm initiation. In addition, we have transposon mutants with insertion into transcription factor genes that showed biofilm reduction. In this work, our objective is to characterize transcription factors and adhesins involved in different stages of biofilm formation and in the adhesion/invasion of C. violaceum in host cells. For this, we will analyze the transcriptome of C. violaceum by RNA-seq, followed by validation by RT-qPCR and EMSA, to identify the regulons of transcription factors involved in biofilm. Null mutants of the genes of interest will be obtained and evaluated for virulence in mouse assays, adhesion and cytotoxicity in cell culture, and biofilm formation. Our data will help to understand the steps of adhesion/invasion in C. violaceum infection.