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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Bactericidal type IV secretion system homeostasis in Xanthomonas citri

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Cenens, William [1] ; Andrade, Maxuel O. [2] ; Llontop, Edgar [1] ; Alvarez-Martinez, Cristina E. [3] ; Sgro, German G. [1] ; Farah, Chuck S. [1]
Total Authors: 6
[1] Univ Sao Paulo, Inst Quim, Dept Bioquim, Sao Paulo, SP - Brazil
[2] Ctr Nacl Pesquisa Energia & Mat, Lab Nacl Biociencias, R Giuseppe Maximo Scolfaro, Campinas, SP - Brazil
[3] Univ Estadual Campinas UNICAMP, Inst Biol, Dept Genet Evolucao Microbiol & Imunol, Rua Monteiro Lobato, Campinas, SP - Brazil
Total Affiliations: 3
Document type: Journal article
Source: PLOS PATHOGENS; v. 16, n. 5 MAY 2020.
Web of Science Citations: 0

Author summary Xanthomonas citri is a member of a family of phytopathogenic bacteria that can cause substantial losses in crops. At different stages of the infection cycle, these cells will encounter other bacterial species with whom they will have to compete for space and nutrients. One mechanism which improves a cell ` s chance to survive these encounters is a type IV secretion system that transfers a cocktail of antimicrobial effector proteins into other Gram-negative bacteria in a contact-dependent manner. Here, we show that this system is constitutively produced at a basal level, even during low nutrient conditions, despite representing a significant metabolic burden to the cell. The conserved global regulator, CsrA, provides a constant, nutrient-independent, repression on the production of T4SS components, thereby holding production costs to a minimum while at the same time ensuring X. citri's competitiveness during encounters with bacterial rivals. Several Xanthomonas species have a type IV secretion system (T4SS) that injects a cocktail of antibacterial proteins into neighbouring Gram-negative bacteria, often leading to rapid lysis upon cell contact. This capability represents an obvious fitness benefit since it can eliminate competition while the liberated contents of the lysed bacteria could provide an increase in the local availability of nutrients. However, the production of this Mega Dalton-sized molecular machine, with over a hundred subunits, also imposes a significant metabolic cost. Here we show that the chromosomal virB operon, which encodes the structural genes of this T4SS in X. citri, is regulated by the conserved global regulator CsrA. Relieving CsrA repression from the virB operon produced a greater number of T4SSs in the cell envelope and an increased efficiency in contact-dependent lysis of target cells. However, this was also accompanied by a physiological cost leading to reduced fitness when in co-culture with wild-type X. citri. We show that T4SS production is constitutive despite being downregulated by CsrA. Cells subjected to a wide range of rich and poor growth conditions maintain a constant density of T4SSs in the cell envelope and concomitant interbacterial competitiveness. These results show that CsrA provides a constant though partial repression on the virB operon, independent of the tested growth conditions, in this way controlling T4SS-related costs while at the same time maintaining X. citri's aggressive posture when confronted by competitors. (AU)

FAPESP's process: 19/12234-2 - Isolation and structural studies on the Xanthomonas citri Type IV pilus and T4SS pilus
Grantee:Edgar Enrique Llontop Cornejo
Support Opportunities: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 15/18237-2 - Genetic elucidation of the functional and regulatory mechanisms underlying the Type IV Secretion System in Xanthomonas citri and how it mediates contact dependent killing
Grantee:William Cenens
Support Opportunities: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 14/04294-1 - Structural and functional studies of the Xanthomonas citri Type IV Secretion System
Grantee:Germán Gustavo Sgro
Support Opportunities: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 17/17303-7 - Structure and function of bacterial secretion systems
Grantee:Shaker Chuck Farah
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 11/07777-5 - Cyclic di-GMP signaling and the Type IV macromolecule secretion system in Xanthomonas citri
Grantee:Shaker Chuck Farah
Support Opportunities: Research Projects - Thematic Grants