Genetical Studies of Non-flagellate Mutants of Salmonella

Transductions were carried out with 22 non-flagellate mutants originating spontaneously from Salmonella typhimurium LT2. Taking the productions of swarm and trail as the criteria of recombination and complementation respectively, the mutants were classified into seven groups, namely flaA, flaB, flaC, flaD, flaF, flaJ and flaK. Each of them may correspond to a cistron. Among them, flaA, B, C, D and J were co-transduced with the structural gene of phase-1 flagellin, HI. Based on the frequency of recombination between two non-flagellate mutants, and that of HI-co-transduction when available, linearly arranged maps of mutant sites in flaA, flaC and flaF were constructed. Co-linearity was demonstrated between the recombination map and complementation map in flaA and flaC, but with some exceptions in flaF. Partial complementation was frequently observed in combination of two mutants in a cistron.

Transductions from thirteen non-flagellate mutants investigated by Joys & Stocker to the above mutants indicated that, among the five complementation groups assigned by them on their mutants, four correspond to our flaA, flaB, flaC and flaD; the remaining one, flaE, is missing in our mutants. Similarly, among eleven mutant sites of the non-flagellate strains of Salmonella abortusequi SL23, ten are distributed in flaA, flaF and flaC. The remaining one, assigned to a mutant of flaG, does not belong to any fla cistrons described above. The recovery of flagellation in the flaG strain by transduction was unsuccessful even when a flagellate strain was used as a donor.

Rabbits were immunized with each of the twenty-one stable non-flagellate mutant clones, and their ability to elicit antiserum specific to flagellar protein was examined by absorption-agglutination test. Among the clones examined, only one belonging to flaG was found to elicit antiserum specific in flagellar antigen of the parental flagellate strain. It was inferred that the flaG mutant can synthesize flagellin but cannot construct flagellar fibres. The remaining fla mutants were presumed to be unable to synthesize flagellin.