Functional activity of E. coli RNase R in the Antarctic Pseudomonas syringae Lz4W

Background In Antarctic P. syringae RNase R play an essential role in the processing of 16S and 5S rRNA, thereby playing an important role in cold-adapted growth of the bacterium. This study is focused on deciphering the in vivo functional activity of mesophilic exoribonuclease R and its catalytic domain (RNB) in an evolutionary distant psychrophilic bacterium Pseudomonas syringae Lz4W. Results Our results confirm that E. coli RNase R complemented the physiological functions of the psychrophilic bacterium P. syringae RNase R and rescued the cold-sensitive phenotype of Pseudomonas syringae ∆ rnr mutant. More importantly, the catalytic domain (RNB) of the E. coli RNase R is also capable of alleviating the cold-sensitive growth defects of ∆ rnr mutant as seen with the catalytic domain (RNB) of the P. syringae enzyme. The Catalytic domain of E. coli RNase R was less efficient than the Catalytic domain of P. syringae RNase R in rescuing the cold-sensitive growth of ∆ rnr mutant at 4°C, as the ∆ rnr expressing the RNB Ec (catalytic domain of E. coli RNase R) displayed longer lag phase than the RNB Ps (Catalytic domain of P. syringae RNase R) complemented ∆ rnr mutant at 4°C. Altogether it appears that the E. coli RNase R and P. syringae RNase R are functionally exchangeable for the growth requirements of P. syringae at low temperature (4°C). Our results also confirm that in P. syringae the requirement of RNase R for supporting the growth at 4°C is independent of the degradosomal complex. Conclusion E. coli RNase R (RNase R Ec ) rescues the cold-sensitive phenotype of the P. syringae Δ rnr mutant. Similarly, the catalytic domain of E. coli RNase R (RNB Ec ) is also capable of supporting the growth of Δ rnr mutant at low temperatures. These findings have a vast scope in the design and development of low-temperature-based expression systems.