Temperature dependence of M pilus formation as demonstrated by electron microscopy

The formation of IncM plasmid encoded pili is dependent on the incubation temperature of the corresponding host strains. By labelling the short, rigid M pili with the donor specific bacteriophage ØM, the presence of pili at 30 °C but not at 37 °C incubation temperature colud be demonstrated for E. coli K 12 substrains carrying different IncM group plasmids. In contrast, such a temperature dependence of M pilus formation is not observed in S. typhimurium substrains.