Genetic Determination ofthe0 Antigens ofSalmo- nella Groups B (4,5,12) andC1(6,7)

MAKELX, P.HELENA(University ofHelsinki, Helsinki, Finland). Genetic determination ofthe 0 antigens ofSalmonella groupsB (4,5,12) andC1(6,7). J.Bacteriol. 91:1115-1125. 1966.-Thegenetic determination ofthe0 antigens of Salmonella was studied byHfrorF'crossesbetween strains ofgroupsB (antigens 4,5,12) andCl(antigens 6,7). Themaingenetic determinants ofthespecificities 4ofgroupBand7ofgroupC1behaved asalleles ofonelocus, called 0 or0-4/7. Thisisprobably identical with0-4/9, responsible fortheserological difference between groupsB andD,andwiththe"rough" locus rouB. Atleast partsofthe antigens 12ofgroupB and62ofgroupC aredetermined atthesame locus. The gene0-5isclosely linked to0-4/7, bothmapping intheapproximately 2minutes distance between hisandmetGintheorder his - 0-4/7 - 0-5- metG.Incrossesof groupB donors withgroupC1recipients, a serologically new type,called semirough(SR), appeared inmostrecombinants thathadinherited the0-4allele of thegroupB donor. TheseSRforms areserologically intermediate between smooth androughforms, showing poorstability insaline butpossessing thespecificities 4and12and(some ofthem)5.On thebasis ofprevious biochemical studies, the hypothesis hasbeenputforward thatthesidechains oftheir lipopolysaccharide aremuchshorter thannormalgroupB sidechains, probably containing only one repeating unit persidechain. A geneSR-4responsible fortheelongation ofgroup B sidechains beyond thefirst repeating unit was mappedbetween galandtry, groupB andD bacteria being SR-4+, andgroupC being SR-4-.