Bacterial conjugation is a sophisticated process that facilitates horizontal gene transfer between bacterial cells and is also responsible for the proliferation of antibiotic resistance genes among the bacterial population. Conjugation is a process of unidirectional transfer of single-stranded DNA from donor cells to recipient cells either via a contact-dependent manner or through the pilus lumen in physically distant cells. A model system for the conjugation mechanism is the F-plasmid of Escherichia coli. The F-plasmid encodes all the genes necessary for its self-transmission. Conjugation in Gram-negative bacteria is carried out by three large complexes, the relaxosome, which processes the plasmid DNA for transfer, the type IV secretion system (T4SS) that translocates the processed DNA, and a coupling protein that acts like a link between the relaxosome and the T4SS complexes. The conjugational transfer of DNA is mediated by the T4SS, one of the most versatile and elaborate secretion systems in bacterial cell envelopes. The T4SS assembles a highly dynamic filamentous structures (T4SS pilus) that undergo cycles of extension and retraction. In a previous study, using cryo-electron tomography(cryo-ET) and sub-tomogram averaging, the F-plasmid encoded T4SS was investigated in Escherichia coli cells. In this study, various T4SS intermediate/relic subcomplexes were observed. However, the biogenesis and disassembly mechanism of the T4SS remain unknown. We aim to investigate the pED208 and F plasmid systems in Salmonella typhimurium to understand the biogenesis and recycling mechanism of the T4SS. The results of this project will allow us to identify potential drug targets for the development of novel conjugation inhibitors, which will enable us to combat the antibiotic resistance crisis.