LTR depends on the absolute temperature and persists as long as the stress exists, and the proteins induced are usually involved in cellular metabolism and membrane functionality ( 43). There are two classes of responses involved in cold adaptation, named low-temperature response (LTR) and cold shock response (CSR) ( 43). Low temperature interferes with cell physiology by affecting several molecules in their biochemical and physical properties, resulting in modifications in general metabolism. Temperature downshift causes growth and cell proliferation arrest, also altering the pattern of protein expression ( 29). crescentus cold adaptation, mechanisms of regulation, and pattern of expression during the acclimation phase apparently differs in many aspects from what has been described so far for other bacteria.įree-living organisms must be able to cope with a multitude of environmental changes, which include nutrient starvation, osmolality imbalance, and temperature shifts, and responses to these stresses require a fine-tuned expression of specific genes ( 30). This work shows that the importance of CspA and CspB to C. In contrast to what was reported for other bacteria, these cold shock genes have no regulatory regions downstream from ATG that are important for cold induction. Deletion mapping of the long 5′-untranslated region (5′-UTR) of each gene identified a common region important for cold induction, probably via translation enhancement. Gene expression analyses were carried out using cspA and cspB regulatory fusions to the lacZ reporter gene and showed that both genes are regulated at the transcriptional and posttranscriptional levels. The cspA cspB double mutant has a slightly more severe phenotype than that of the cspA mutant, suggesting that although CspA may be more important to cold adaptation than CspB, both proteins have a role in this process. The deletion of cspA causes a decrease in growth at low temperature, whereas the strain with a deletion of cspB has a very subtle and transient cold-related growth phenotype. In this work we have determined that the synthesis of both CspA and CspB reaches the maximum levels early in the acclimation phase. Caulobacter crescentus has four CSPs: CspA and CspB, which are cold induced, and CspC and CspD, which are induced only in stationary phase. Cold shock proteins (CSPs) are nucleic acid binding chaperones, first described as being induced to solve the problem of mRNA stabilization after temperature downshift.
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