1 Department of Systems Biology, Technical University of Denmark2 Drug Resistance and Community Dynamics, Department of Systems Biology, Technical University of Denmark3 Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark4 Projects, Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark5 Bacterial Cell Factories, Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark6 Center for Systems Microbiology, Department of Systems Biology, Technical University of Denmark
Bacterial conjugation in the human gut microbiota is believed to play a major role in the dissemination of antibiotic resistance genes and virulence plasmids. However, the modulation of bacterial conjugation by the human host remains poorly understood and there is a need for controlled systems to study this process. We established an in vitro co-culture system to study the interaction between human intestinal cells and bacteria. We show that the conjugation efficiency of a plasmid encoding an extended spectrum beta-lactamase is reduced when clinical isolates of Escherichia coli are co-cultured with human intestinal cells. We show that filtered media from co-cultures contain a factor that reduces conjugation efficiency. Protease treatment of the filtered media eliminates this inhibition of conjugation. This data suggests that a peptide or protein based factor is secreted on the apical side of the intestinal cells exposed to bacteria leading to a two-fold reduction in conjugation efficiency. These results show that human gut epithelial cells can modulate bacterial conjugation and may have relevance to gene exchange in the gut.