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Composition and function of Vibrio cholerae biofilms on human macrophages

Subject Area Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology
Parasitology and Biology of Tropical Infectious Disease Pathogens
Metabolism, Biochemistry and Genetics of Microorganisms
Term from 2020 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 442780977
 
Final Report Year 2024

Final Report Abstract

This project characterized the interaction between Vibrio cholerae and human immune cells, particularly macrophages. The project led to several important scientific advances, which are described in detail our project publication, and summarized here: 1. V. cholerae forms biofilms on human immune cells. The study highlights that V. cholerae forms biofilms on macrophages through a sequential process that mirrors biofilm development on abiotic surfaces. This process involves initial attachment, growth into three-dimensional structures, and eventual dispersal. Attachment to macrophages is facilitated by flagella motility and two types of type IV pili: the mannose-sensitive hemagglutinin (MSHA) pilus and the toxincoregulated (TC) pilus. The presence of either pili, along with flagella, is essential for the initial attachment phase. 2. The biofilm composition on macrophages differs from biofilms on other surfaces. In contrast to V. cholerae biofilms formed on other surfaces, the Vibrio polysaccharide VPS and the proteins RbmA, RbmC, and Bap1 are not a significant part of the biofilm matrix on macrophages. Instead, the biofilm matrix on macrophages is composed of the MSHA and TC pili. TC pili providing mechanical stability and promoting cell-cell alignment within the biofilm, whereas the MSHA pili do not have a strong impact on mechanical stiffness of the biofilms on macrophages. 3. Mechanism of biofilm dispersal from macrophages. Biofilm dispersal on macrophages is achieved by the downregulation of TC pili and a reduction in intracellular levels of the signaling molecule c-di-GMP. 4. Function of biofilm formation on macrophages. We discovered that biofilm formation on macrophages enhances the killing of macrophages by increasing the delivery of the hemolysin toxin HlyA. This toxin plays a crucial role in macrophage death, and the presence of biofilms significantly amplifies its lethal effect. 5. Established organoid model for V. cholerae infection. The development of a small intestine organoid from human stem cells, which was achieved in this project, is an important tool for studying V. cholerae infection mechanisms. Beyond the scientific advances that were delivered by this project, the project results have potential routes for applications, in improving therapeutic applications for the cholera disease, by interfering with the MSHA pili and TC pili, which are important for biofilm formation on macrophages. Furthermore, the establishment of the small intestinal organoid system for characterizing V. cholerae infection processes, including epithelial and immune cells.

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