Ferric Uptake Regulator Fur Coordinates Siderophore Production and Defense against Iron Toxicity and Oxidative Stress and Contributes to Virulence in Chromobacterium violaceum

Author(s)

Rodrigues de Souza Santos, Renato Elias ^[1] ; Batista, Bianca Bontempi ^[1] ; da Silva Neto, Jose Freire ^[1]

Affiliation

^[1] Univ Sao Paulo, Fac Med Ribeirao Preto, Dept Biol Celular & Mol & Bioagentes Patogen, Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: Applied and Environmental Microbiology; v. 86, n. 21 NOV 2020.
• Web of Science Citations: 0

Abstract

Iron is a highly reactive metal that participates in several processes in prokaryotic and eukaryotic cells. Hosts and pathogens compete for iron in the context of infection. Chromobacterium violaceum, an environmental Gram-negative bacterial pathogen, relies on siderophores to overcome iron limitation in the host. In this work, we studied the role of the ferric uptake regulator Fur in the physiology and virulence of C. violaceum. A.fur mutant strain showed decreased growth and fitness under regular in vitro growth conditions and presented high sensitivity to iron and oxidative stresses. Furthermore, the absence of fur caused derepression of siderophore production and reduction in swimming motility and biofilm formation. Consistent with these results, the C. violaceum.fur mutant was highly attenuated for virulence and liver colonization in mice. In contrast, a manganese-selected spontaneous fur mutant showed only siderophore overproduction and sensitivity to oxidative stress, indicating that Fur remained partially functional in this strain. We found that mutations in genes related to siderophore biosynthesis and a putative CRISPR-Cas locus rescued the.fur mutant growth defects, indicating that multiple Fur-regulated processes contribute to maintaining bacterial cell fitness. Overall, our data indicated that Fur is conditionally essential in C. violaceum mainly by protecting cells from iron overload and oxidative damage. The requirement of Fur for virulence highlights the importance of iron in the pathogenesis of C. violaceum. IMPORTANCE Maintenance of iron homeostasis, i.e., avoiding both deficiency and toxicity of this metal, is vital to bacteria and their hosts. Iron sequestration by host proteins is a crucial strategy to combat bacterial infections. In bacteria, the ferric uptake regulator Fur coordinates the expression of several iron-related genes. Sometimes, Fur can also regulate several other processes. In this work, we performed an in-depth phenotypic characterization of fur mutants in the human opportunistic pathogen Chromobacterium violaceum. We determined that fur is a conditionally essential gene necessary for proper growth under regular conditions and is fully required for survival under iron and oxidative stresses. Fur also controlled several virulence-associated traits, such as swimming motility, biofilm formation, and siderophore production. Consistent with these results, a C. violaceum fur null mutant showed attenuation of virulence. Therefore, our data established Fur as a major player required for C. violaceum to manage iron, including during infection in the host. (AU)

• FAPESP's process: 17/03342-0 - The Fur family of transcription factors and the response to iron and zinc in Chromobacterium violaceum
• Grantee: Renato Elias Rodrigues de Souza Santos
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 18/01388-6 - Iron homeostasis in Chromobacterium violaceum: regulatory mechanisms, uptake systems and role in virulence
• Grantee: José Freire da Silva Neto
• Support type: Regular Research Grants
• FAPESP's process: 20/00259-8 - Role of secretion systems of Chromobacterium violaceum in the interaction with the host and other bacteria
• Grantee: José Freire da Silva Neto
• Support type: Regular Research Grants
• FAPESP's process: 18/19058-2 - Characterization of novel mechanisms of regulation and resistance to iron in Chromobacterium violaceum
• Grantee: Bianca Bontempi Batista
• Support type: Scholarships in Brazil - Doctorate