Serological and finger-printing analyses of mutant flagellar antigens of Salmonella.

SUMMARY: Spontaneous mutants with altered flagellar antigen were isolated from a phase-1 stable Salmonella strain, tr 6, whose phase-1 antigen consists of at least three antigenic factors, g3, g4 and f. Three kinds of antisera reacting with each of these factors were used as the selective agents. The mutants were isolated by picking from swarms in semisolid medium containing the respective antisera. Mutants were classified into two groups. A group comprising four mutants selected with antiserum to g3 and two mutants selected with antiserum to g4, in which all three antigenic factors examined were simultaneously altered; and a second group comprising all the other mutants, in which only a single factor corresponding to the selective antiserum was altered. All the altered factors retained weak cross-reactivity with the original factors. In all cross-absorption-agglutination tests between each of the mutant antigens and the wild-type antigen, activity of the antisera was fully absorbed, showing that the mutant antigens had neither lost any antigenic specificities nor gained any new specificity. Transductional analysis showed that the sites of mutation were inseparable from H 1, the structural gene for phase-1 flagellin. Tryptic peptide patterns of flagellins of two mutants were compared with that of the wild-type strain and a difference of one or two peptides was detected. From these results it is concluded that these mutants possessed a minor change in primary structure of flagellin which resulted from a mutation in the H 1 gene.