The R-bodies of Xanthomonas citri

• Grant number: 19/09482-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2019
• End date: November 10, 2021
• Field of knowledge: Biological Sciences - Biochemistry - Molecular Biology
• Principal Investigator: Shaker Chuck Farah
• Grantee: Sofia Quarello dos Ramos
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 17/17303-7 - Structure and function of bacterial secretion systems, AP.TEM

Abstract

R-bodies are insoluble, proteinaceous bodies that form cylindrical bundles that can reversibly unwind and wind in response to specific conditions such as pH, ionic strength, the presence or absence of certain ions and temperature. This protein structure was initially observed in obligate endosymbiotic bacteria of the species Caedibacter taeniospiralis (called Kappa particles) in "killer" strains of Paramecium. When "sensitive" Paramecium strains incorporate C. taeniospiralis into digestive vacuoles, the acidity of the medium results in bacterial death and R-body unwinding, breaking the vacuole and the host's membrane, along with the release bacterial toxins within the protozoa.In C. taeniospiralis R-bodies are formed of polymers of the products of rebA and rebB genes and their production R-bodies depend on the rebABCD cluster. Over the last five years, homologs of these genes have been identified in many other free-living environmental bacterial species as well as phytopathogenic species, such as those of the genus Xanthomonas. In Xanthomonas citri species, two loci encoding a total of up to 7 homologs of rebA and rebB were identified. To date, there are no studies on the physiological functions of these reb homologs in species of this bacterial genus. However, given that X. citri, the agent responsible for citrus canker disease, occupies niches in which it competes with other micro-organisms (bacteria, fungi, amoebas, etc.), our group is interested in investigating the possible importance of R-bodies in mechanisms of defense against protozoa. The main goal of this undergraduate research project is to study the behavior of R-bodies in X. citri. Biochemical and functional studies will be carried out on purified R-bodies as well as genotypic and phenotypic analyses of mutant and knockout strains.