Regulation of sulfur assimilation pathways in Salmonella enterica serovar Typhi upon up-shift high osmotic treatment: the role of UhpA revealed through transcriptome profiling.

Salmonella species were the most deeply and extensively studied prokaryotes, which were used as useful prokaryotic models for the genetic analysis. Salmonella enterica serovar Typhi (S. Typhi) is the etiological agent of typhoid fever, a major health problem in developing countries. UhpB/UhpA couple is a member of two-component regulatory system. It is considered that UhpB/UhpA controls the expression of the transport protein UhpT, which enables the cell to acquire phosphorylated sugars from its environment that can be used as carbon and/or energy sources. In our previous microarray-based study, uhpA and uhpB were up-regulated in S. Typhi at early stage of an osmotic up-shift stress. To explore the functions of UhpA under this stress, we constructed an uhpA deletion mutant of S. Typhi, and compared the global transcriptional difference between the uhpA mutant strain and the wild-type strain upon the up-shift high osmotic stress by using a genomic DNA microarray. Only 21 genes showed significant expression differences in the uhpA mutant strain compared to the wild-type strain. Strikingly, these 21 genes were all down-regulated (twofold). Moreover, most of these genes were associated with sulfur assimilation pathways. The results were validated by quantitative real-time PCR. In this study, we first found that uhpA involved in regulating sulfur assimilation pathways upon up-shift high osmotic treatment for 30 min, which will further promote our insights into the regulator network of S. Typhi.