f Development of Flagella by Proteus mirabilis

SUMMARY: The sequence of flagellar development accompanying differentiation during multiplication in a plate culture of Proteus mirabilis was investigated with the electron microscope and the negative-staining technique; the sequence of development can best be seen from the electron micrographs. The first flagella were produced towards the end of the first hour, and increased to a peak at about 6 hr and then decreased. The bacteria changed from coccoid to rod-shaped to elongated forms; the latter measured up to 80 μ, in length and were equipped with several thousand flagella. On the basis of measurements of flagellar complement, the elongated forms (or swarmers) can be regarded as ‘flagellin-factories’. The fine structure of both flagella and fimbriae was examined and several new features were seen, in particular certain structures at the bases of both appendages. The diameter of Proteus fimbriae was found to be about 40 Å.