Identification of Salmonella enterica Serovar Typhi DNA Fragments with Transcriptional Activity Under Different Growth Conditions.

Abstract: Salmonella enterica serovar Typhi is a human pathogenic microorganism with a very complex infective cycle, involving the transit of bacteria across different microenvironments; to optimize the performance of attenuated Salmonella strains suitable as live carriers of heterologous antigens, fine tuning of wild type bacteria gene expression is essential. Several DNA fragments were obtained from a Salmonella enterica serovar Typhi (vi+, fim+) blood isolate and 18 clones were selected according to the dimension of the insert (range <0.2-1.6 kb). These fragments showed a transcriptional activity in a promoterless vector cloned in Escherichia coli background, according to homogeneous parameters. The results obtained provide an insight about signals mediating gene activation in vivo, particularly in the microenvironments known to exist during the infectious process, even if the fragments are not promoters sequences. Finally, the functional characterization of several fragments showed that they possessed an efficient and homogeneous transcriptional activity, worth to be further investigated.