The Isolation and Characterization of Mutants of Bacillus subtilis and Bacillus licheniformis with Disturbed Morphology and Cell Division

SUMMARY

Mutants (rod) have been isolated from one strain of Bacillus subtilis and two of B. licheniformis after treatment with I-methyl-3-nitro-I-nitroso-guanidine, by replica plating from media containing 0·8 M-NaCl to media of low salt content. When grown on the latter media these mutants appear as groups or strings of coccal bodies which, when examined in section under the electron microscope, show gross distortions in their walls and membranes; septum formation is greatly disorganized. When grown in media containing 0·8 to I·O M-NaCl, or KCl, or ample supplies of organic nitrogen, considerable correction of the morphology of one class of these mutants occurs. The other class of mutants is not changed to rods by growth in media of high salt content but is so changed by growth on rich media containing yeast extract. All the mutants revert to the parent type, but at very different rates. The physiological characteristics of the mutants and the parents are in most respects identical.