A New Type of Flagellar Variation associated with New Antigens in the Salmonella Group

SUMMARY: A new type of phase variation which changes in one direction only has been noted in some members of the Salmonella group. This was found in association with three hitherto undescribed flagellar antigens, z43, z45 and z46, which are characterized. These occurred naturally with particular frequency in Salmonella group E and in cultures which possessed an alternate g, s, t phase. Two of these antigens, z43 and z45, were found less frequently in other O groups and in organisms possessing other alternative phases. Although the antigens in question can be readily transformed to the alternate phases of the organisms in which they occur, these alternate phases could not be changed to z43, z45 or z46.