Determination of the Activity of the fimF Gene and Its N-Terminal Domain Disrupted Mutant on Biofilm Formation and Its Contribution to the Oxidative Stress Response in S. Typhimurium

Abstract

Fimbriae is an important virulence factor which plays a key role in cell attachment and colonization of the intestinal mucosa during an infection of Salmonella, a pathogen that causes gastroenteritis and systemic infection in humans. In S. Typhimurium, type 1 fimbriae production strengthens the oxidative stress response. This study aimed to determine the effectiveness of the fimF gene and its N-terminal domain on biofilm formation in S. Typhimurium and their contribution to the oxidative stress response. Before the experiments to prove whether the N-terminal domain of the FimF protein is the region that determines the mechanism and function of the fimF gene; only the N-terminal domain of the fimF gene was cloned behind the pBAD promoter. As a result of biofilm experiments on polystyrene surfaces, it was determined that the biofilm production capacity was reduced significantly in mutant strains in terms of fimF and dam genes (p < 0.05). In the oxidative stress response experiment conducted in the presence of hydrogen peroxide (H2O2), it was determined that the mutant strains were more resistant to hydrogen peroxide than the wild-type strain, therefore Salmonella cells perceived the absence of Dam methylase enzyme and FimF protein as a critical internal stress condition and produced strong responses to these stress conditions. As a result of comparative analysis of the N-terminal domain cloned mutant strain with the wild-type, it was proven that the N-terminal domain of the protein in question acts as an adapter protein, due to its close similarities with the wild-type.