Function of Salmonella bongori SPI-22 T6SS in bacterial competitions and interactions with phagocytic host cells

• Grant number: 19/22715-8
• Support type: Scholarships in Brazil - Master
• Effective date (Start): December 01, 2019
• Effective date (End): January 31, 2022
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal researcher: Ethel Bayer Santos
• Grantee: Daniel Enrique Sánchez Limache
• Home Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 17/02178-2 - Function of type VI secretion systems of pathogenic bacteria in the interaction with eukaryotic cells, AP.JP

Abstract

Bacterial secretion systems are versatile structures that can secrete proteins into the extracellular medium or into prokaryotic and eukaryotic cells. The type VI secretion system (T6SS) is present in several animal and plant pathogens. Salmonella enterica serotypes comprise facultative intracellular Gram-negative bacteria responsible for causing infections in various vertebrates. The genus Salmonella comprises two species: S. bongori and S. enterica, with S. enterica being subdivided into six subspecies. Most serotypes of S. enterica subsp. enterica encode a T6SS from the pathogenicity island SPI-6 (Salmonella pathogenicity island 6). However, in other serotypes and subspecies distinct T6SSs are found encoded from other pathogenicity islands such as SPI-19, SPI-20 and SPI-21. S. bongori encodes a T6SS from SPI-22. Phylogenetic analyzes suggest that these systems were acquired by different horizontal transfer events and could perform distinct functions. S. bongori is mainly associated with cold-blooded animal infections. This species does not encode one of the type 3 secretion systems (SPI-2 T3SS) contained in S. enterica, which is required for multiplication within macrophages. Interestingly, comparative genomics analyzes revealed that SPI-22 T6SS is inserted into the locus where SPI-2 T3SS is located in S. enterica. There is no information in the literature about the function of S. bongori SPI-22 T6SS. In this context, this project aims to investigate whether this system is functional and whether it targets prokaryotic or eukaryotic cells. These results would help explain the evolution of the acquisition of different virulence factors by Salmonella species, and the characterization of new virulence factors used by these bacteria to maintain environmental reservoirs. (AU)