In its natural habitats (soil, water and rhizosphere), Pseudomonas putida can suffer frequent and long-term changes in temperature that affect its growth and survival. Pseudomonas putida KT2440, a well-characterized model strain, grows optimally at 30°C but can proliferate at temperatures as low as 4°C. However, little information is available on the physiological changes that occur when P. putida grows at low temperatures. To investigate this area, the transcriptome and proteome profiles of cells exponentially growing in a complex medium at 10°C were compared with those of cells exponentially growing at 30°C. Low temperature modified the expression of at least 266 genes (some 5% of the genome). Many of the genes showing differential expression were involved in energy metabolism or in the transport and binding of substrates, although genes implicated in other cellular functions were also affected. Several changes seemed directed towards neutralizing problems created by low temperature, such as increased protein misfolding, the increased stability of DNA/RNA secondary structures, reduced membrane fluidity and a reduced growth rate. The present results improve our understanding of the P. putida lifestyle at low temperature, which may be relevant for its applications in bioremediation and in promotion of plant growth.