Genetic analysis of the pnpdeaD genetic region reveals membrane lipoprotein NlpI as an independent participant in cold acclimatization of Salmonella enterica serovar Typhimurium


Correspondence: Mikael Rhen, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Box-280, SE-17 177 Stockholm, Sweden. Tel.: +46 8 52486252; fax: +46 8 330498; e-mail:


The cold acclimatization response in many bacterial species is a tightly regulated process, which ensures the correct folding of macromolecules. In enterobacteria, this response is in part dependent on polynucleotide phosphorylase, which is encoded by the gene pnp. Based on transcriptional analysis of the pnp locus of Salmonella enterica serovar Typhimurium, we show that pnp and the adjacent membrane lipoprotein nlpI gene form an operon with both genes contributing independently to the cold acclimatization response at 15 °C. Our findings thereby define a new role for NlpI in bacterial cold acclimatization.