Polynucleotide phosphorylase-deficient mutants of Pseudomonas putida

In bacteria, polynucleotide phosphorylase (PNPase) is one of the main exonucleolytic activities involved in RNA turnover and is widely conserved. In spite of this, PNPase does not seem to be essential for growth if the organisms are not subjected to special conditions, such as low temperature. We identified the PNPase-encoding gene (pnp) of Pseudomonas putida and constructed deletion mutants that did not exhibit cold sensitivity. In addition, we found that the transcription pattern of pnp upon cold shock in P. putida was markedly different from that in Escherichia coli. It thus appears that pnp expression control and the physiological roles in the cold may be different in different bacterial species.