Investigation of temperature-regulated mechanisms in Yersinia pseudotuberculosis

Pathogenic bacteria are confronted with frequently changing conditions during infection of warm-blooded hosts and after excretion into the environment. They therefore must be able to respond to these changes rapidly and adapt their metabolism accordingly. Among various environmental factors, temperature plays an important role. Bacteria can react to changes in temperature at different levels of regulation. At the DNA level, transcription factors can up- or downregulate gene expression. At the RNA level, non-coding RNAs, such as small regulatory RNAs (sRNAs) and RNA thermometers (RNATs) can have a post-transcriptional effect on the translation efficiency of various mRNAs through temperature-induced conformational changes.

Yersinia pseudotuberculosis is a food-borne human pathogen that can lead to diseases of the gastrointestinal tract and the intestinal lymphatic system. Its optimum growth temperature is ~28 °C, but the cells can quickly react to an increase in host temperature to 37 °C and adapt their metabolism and virulence. In addition, Y. pseudotuberculosis can survive cold temperatures, allowing growth on food in the refrigerator.

While some regulatory mechanisms of Y. pseudotuberculosis are well described once the cells are taken up from the environment by a host, we aim to determine how the bacterium reacts when it is released from the host to low temperatures in the environment. RNA-Seq revealed numerous genes that might play an important role for Yersinia within 30 min after the temperature is reduced from 37 °C to 25 °C, 17 °C or 10 °C.

We are also interested in the function of the outer membrane protein OmpX of Y. pseudotuberculosis. It is primarily produced at 25 °C due to the temperature-mediated regulation by the sRNA CyaR (1). Interestingly, Yersinia produces a structurally similar, virulence-related protein, Ail, at 37 °C, which is upregulated by an RNAT. To examine the reciprocal production of OmpX and Ail at 25 °C or 37 °C, respectively, we carry out phenotypic characterizations of mutant strains to understand a potential connection between these outer membrane proteins. We found that single or combined deletions of both genes lead to an increased sensitivity at elevated salt concentrations.

(1) Guanzon et al. Two temperature-responsive RNAs act in concert: The small RNA CyaR and the mRNA ompX bioRxiv 2024