Biological and virulence characteristics of Salmonella enterica serovar Typhimurium following deletion of genes encoding the tRNA modification enzymes GidA and MnmE

Salmonella is a major foodborne pathogen causing public health problems throughout the world due to the consumption of contaminated food. In Escherichia coli, GidA and MnmE have been shown to bind together to modify tRNA. We have previously shown that deletion of gidA attenuated Salmonella virulence in both in vitro and in vivo models of infection due to a significant down-regulation of virulence genes and proteins. Furthermore, immunization with the gidA mutant strain protected mice from a lethal dose challenge of wild-type Salmonella, and a filamentous morphology was observed in the gidA mutant cells. Therefore, we hypothesize that GidA and MnmE have a significant role in the biology and virulence of Salmonella.;In this study we conducted a characterization of GidA and MnmE in Salmonella. This is the first study to perform an investigation into the biological activities of GidA and MnmE in Salmonella. The objectives of our current research were to: 1.) Determine the molecular mechanism by which GidA affects Salmonella morphology; 2.) Determine the immunological basis of protection provided by vaccination with the gidA mutant; 3.) Investigate the role of GidA and MnmE in the modulation of Salmonella pathogenesis; 4.) Determine the subcellular localization of GidA and MnmE.;Our data indicate GidA is a potential regulator of Salmonella cell division genes, and the filamentous nature of the gidA mutant cells is most likely due to a defect in chromosome segregation. We showed that the gidA mutant strain is a good candidate for use in a live-attenuated vaccine as immunization with the gidA mutant strain conferred protective immunity in mice by eliciting both humoral and cell-mediated immune responses. Furthermore, the GidA and MnmE proteins bind together to modify Salmonella tRNA as part of a regulatory pathway responsible for Salmonella pathogenesis. Finally, we characterized the subcellular localization of GidA and MnmE as cytoplasmic proteins associated with the cell membrane.;Overall, data from this study characterized a key pathogenic regulatory mechanism in Salmonella which could help in the design of effective preventative treatments against salmonellosis.