Abstract
Urease acts as an important acid resistance system and virulence factor that is widespread among microorganisms. RovM is a global regulator that regulates a series of genes and pathways including acid survival systems in the enteric bacterium Yersinia pseudotuberculosis (Yptb). However, whether RovM regulates the urease activity in Yptb was still unknown. In this study, by using qualitative and quantitative urease assays, we show that the urease expression responds to nutrient conditions and the RovM protein represses urease expression by binding to its promoter. A previously reported positive regulator OmpR activates urease activity but RovM plays a dominant role in different nutrient conditions. In addition, carbon storage regulator system A (CsrA), the upstream regulator of RovM, dramatically down-regulates urease activity possibly by its binding to the Shine-Dalgarno (SD) sequence of the mRNA encoding the urease. In conclusion, this study demonstrates that urease activity is strictly controlled by nutrient conditions and is down-regulated by the CsrA-RovM pathway.
Highlights
Yersinia pseudotuberculosis (Yptb) is a Gram-negative enteropathogenic bacterium and main transmitted through the contacting with infected animals and eating contaminated food (Fukushima et al, 1988; Fukushima and Gomyoda, 1991; Laukkanen et al, 2008)
We found that urease expression is dependent on nutrient conditions and the urease activity is negatively regulated by RovM and carbon storage regulator system A (CsrA) in Yptb
As urease acts as an important acid tolerance system, we asked whether it responds to nutrient signals
Summary
Yersinia pseudotuberculosis (Yptb) is a Gram-negative enteropathogenic bacterium and main transmitted through the contacting with infected animals and eating contaminated food (Fukushima et al, 1988; Fukushima and Gomyoda, 1991; Laukkanen et al, 2008). Given the fact that food-borne pathogens must withstand stomach acidity, survival in acidic conditions is essential for Yptb. To counteract this acidic condition, bacteria have developed sophisticated acid resistance systems (Bearson et al, 1997). At least four acid resistance (AR) systems, named AR1 to AR4 are generally recognized, which are known to allow the bacteria survival under extremely acidic conditions (reviewed in Foster, 2004; Zhao and Houry, 2010). Four clusters of Type VI secretion system (T6SS-1 to T6SS-4) have been identified in Yptb (Zhang et al, 2011) Recently, the T6SS-4 was reported to play a role in resistance to mild acid stress which was activated by OmpR to maintain cell functions in Yptb (Zhang et al, 2013)
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