THE COLD SHOCK RESPONSE OF THE PSYCHROTROPHIC BACTERIUM PSEUDOMONAS-FRAGI INVOLVES 4 LOW-MOLECULAR-MASS NUCLEIC-ACID BINDING-PROTEINS

The psychrotrophic bacterium Pseudomonas fragi was subjected to cold s hocks from 30 or 20 to 5 degrees C. The downshifts were followed by a lag phase before growth resumed at a characteristic 5 degrees C growth rate. The analysis of protein patterns by two-dimentional gel electro phoresis revealed overexpression of 25 or 17 proteins and underexpress ion of 12 proteins following the 30- or 20-to-5 degrees C shift, respe ctively. The two downshifts shared similar variations of synthesis of 20 proteins. The kinetic analysis distinguished the induced proteins i nto cold shock proteins (Csps), which were rapidly but transiently ove rexpressed, and cold acclimation proteins (Caps), which were more or l ess rapidly induced but still overexpressed several hours after the do wnshifts. Among the cold-induced proteins, four low-molecular-mass pro teins, two of them previously characterized as Caps (CapA and CapB), a nd heat acclimation proteins (Haps) as well as heat shock proteins (Hs ps) for the two others (TapA and TapB) displayed higher levels of indu ction. Partial amino acid sequences, obtained by microsequencing, were used to design primers to amplify hy PCR the four genes and then dete rmine their nucleotide sequences. A BamHI-EcoRI restriction fragment o f 1.9 kb, containing the complete coding sequence for capB, was cloned and sequenced. The four peptides belong to the family of small nuclei c acid-binding proteins as CspA, the major Escherichia coli Csp. They are likely to play a major role in the adaptative response of P. fragi to environmental temperature changes.