Abstract
Yersinia pseudotuberculosis is a significant psychrotrophic food pathogen whose cold tolerance mechanisms are poorly understood. Signal transduction systems serve to monitor the environment, but no systematic investigation of their role at cold temperatures in Y. pseudotuberculosis has yet been undertaken. The relative expression levels of 54 genes predicted to encode proteins belonging to signal transduction systems in Y. pseudotuberculosis IP32953 were determined at 28°C and 3°C by quantitative real-time reverse transcription-PCR. The relative expression levels of 44 genes were significantly (p<0.05) higher at 3°C than at 28°C. Genes encoding the two-component system CheA/CheY had the highest relative expression levels at 3°C. Mutational analysis revealed that cheA is important for growth and motility at 3°C. The relative expression level of one gene, rssB, encoding an RpoS regulator, was significantly (p<0.05) lower at 3°C than at 28°C. The results suggest that several signal transduction systems might be used during growth at low temperature, and at least, CheA/CheY two-component system is important for low-temperature growth.
Highlights
Yersinia pseudotuberculosis is an important food-borne pathogen capable of growing at refrigeration temperatures and under modified atmospheres [1]
Little is known about the cold tolerance mechanisms of Y. pseudotuberculosis, key changes reported to occur in Enterobacteriaceae during adaptation to growth at cold temperatures include an increase in low-melting-point lipids in cell membranes and accumulation of compatible solutes in the cells [1]
The relative expression levels of cheA and cheY, which encode a CheA/CheY two-component system involved in chemotaxis, were 31- and 25-fold higher, respectively, at 3uC than at 28uC. 16S rRNA gene was used as a normalization reference for RT-qPCR
Summary
Yersinia pseudotuberculosis is an important food-borne pathogen capable of growing at refrigeration temperatures and under modified atmospheres [1]. Two-component signal transduction systems are widespread among bacteria and help them monitor and adapt to changes in their extra- or intracellular environment [10]. A classical two-component system consists of a sensor histidine kinase and a response regulator located in the cell membrane and cytoplasm, respectively [10]. The phosphoryl group is transferred to the response regulator, which activates and binds to the DNA, resulting in changes in transcription [10]. A variant of the classical two-component system is a multistep phosphorelay consisting of a hybrid histidine kinase, a histidine phosphotransferase, and a response regulator [10]. Predicted by in silico analysis, the Y. pseudotuberculosis strain IP32953 has 24 complete signal transduction systems and 5 orphan hybrid histidine kinases or response regulators [12]
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