Control of temperature-dependent synthesis of K99 fimbriae

The influence of temperature on the production of K99 fimbriae by Escherichia coli was determined in cultures growing at constant specific growth rate in continuous cultures. In a wild type strain, in which the K99 operon is present on a low copy number plasmid, low cultivation temperature repressed the K99 production. This temperature-dependent production was not observed after introduction of multicopies of the regulatory region of the K99 operon into this strain, nor in E. coli K12 harbouring a recombinant, multicopy plasmid encoding the K99 operon. These results are in agreement with a regulation model in which a regulatory factor, most likely a repressor, inhibits expression of the K99 operon at low temperatures.