One of these cold shock proteins, CspA (CS 7,4), ap-

Abstract The hns gene is a member of the cold-shock regulon, indicating that the nucleoid-associated, DNA-binding protein H-NS plays an important role in the adaptation of Escherichia coli to low temperatures. We show here that the ability to cope efficiently with a cold environment (12°C and 25°C) is strongly impaired in E. coli strains carrying hns mutations. Growth inhibition is much more pronounced in strains carrying the hns-206 allele (an ampicillin resistance cassette inserted after codon 37) than in those carrying the hns-205 mutation (a Tnl0 insertion located in codon 93). A protein frag-ment (H-NS*) is synthesized in strains carrying the hns-205::Tn10 mutation, suggesting that this truncated polypeptide is partially functional in the cold adapta-tion process. Analysis of the growth properties of strains harbouring four different low-copy-number plasmid-en-coded hns ' genes that result in the production of C-ter-minally truncated H-NS proteins supports this pro-posal. H-NS * proteins composed of 133, 117 or 94 amino-terminal mino acids partially complemented the severe cold-sensitive growth phenotype of the hns-206 mutant. In contrast, synthesis of a truncated H-NS protein with only 75 amino-terminal mino acids was insufficient to restore growth at low temperature. Key words Adaptation to low temperature DNA-binding protein H-NS • hns mutants Truncated proteins In Escherichia coli, an abrupt switch in the growth tem-perature from 37°C to 10°C arrests growth for 4 to 5 h. During this lag time most protein synthesis inhibited, but the production of at least 13 proteins is transiently increased (for an overview see Jones and Inouye 1994)