Abstract
The bacterial small heat shock protein IbpA protects client proteins from aggregation. Due to redundancy in the cellular chaperone network, deletion of the ibpA gene often leads to only a mild or no phenotypic defect. In this study, we show that a Pseudomonas putida ibpA deletion mutant has a severe growth defect under heat stress conditions and reduced survival during recovery revealing a critical role of IbpA in heat tolerance. Transcription of the ibpA gene depends on the alternative heat shock sigma factor σ32. Production of IbpA protein only at heat shock temperatures suggested additional translational control. We conducted a comprehensive structural and functional analysis of the 5′ untranslated regions of the ibpA genes from P. putida and Pseudomonas aeruginosa. Both contain a ROSE-type RNA thermometer that is substantially shorter and simpler than previously reported ROSE elements. Comprised of two hairpin structures only, they inhibit translation at low temperature and permit translation initiation after a temperature upshift. Both elements regulate reporter gene expression in Escherichia coli and ribosome binding in vitro in a temperature-dependent manner. Structure probing revealed local melting of the second hairpin whereas the first hairpin remained unaffected. High sequence and structure conservation of pseudomonal ibpA untranslated regions and their ability to confer thermoregulation in vivo suggest that short ROSE-like thermometers are commonly used to control IbpA synthesis in Pseudomonas species.
Highlights
Pseudomonads are highly adaptive microorganisms with a high metabolic versatility that enables inhabitation of a wide variety of ecological niches [1]
In most Gram-negative bacteria, transcription of heat shock genes is controlled by the alternative sigma factor s32 (RpoH) [9]
Four hours after stress induction, the cell density of the mutant culture was approximately 60% lower compared to the wild type
Summary
Pseudomonads are highly adaptive microorganisms with a high metabolic versatility that enables inhabitation of a wide variety of ecological niches [1]. To facilitate the reliable prediction of potential RNA structures involved in translational control, the 59 end of the P. putida ibpA transcript was identified using primer extension and 59 RACE (Rapid amplification of cDNA ends) experiments (Fig. 3A and B).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
