Abstract
1. The genetic determinations of the O antigens of Salmonella were studied using Hfr or F' croses between strains of groups B (S. abony : O-1, 4, 5, 12 ; S. paratyphi B var. odense : O-1, 4, 12) and C2 (S, newport var. puerto-rico : O-6, 8). The main genetic determinants of the antigens 4, 12 of group B and 6, 8 of group C2 behaved as alleles of one locus in so-called O, close to his locus. The gene O-5 was also linked to his locus.
2. S. Paratyphi B var. odense (native O antigens 1, 4, 12) of group B which received O-6, 8 from S. newport var. puerto-rico (O-6, 8) of group C2, produced P 22 (iota) without manifestation of O-1, but O-1 was produced after transfer of O antigens 4, 12 or 4, 5, 12 from S. paratyphi B 8006 (O-4, 5, 12) of group B or of O antigens 9, 12 from S. typhi H 901 W (O-9, 12) of group D. The fact was considered that O-1 may be produced through the action of phage P 22 (iota) in co-operation with the substance of O-12.
3. The genetic determination of the O antigens of Salmonella was also studied using Hfr or F' reciprocal crosses between strains of groups B (S. abony : O-1, 4, 5, 12 or S. paratyphi B var. odense : O-1, 4, 12) and C3 (S. emek : O-(8), 20). The main genetic determinants of the antigens 4, 12 of group B and (8) of group C3 behaved as alleles of one locus, called O-4, 12/(8) , and were found to be closely linked to his locus.
4. In crosses of a group B donor (S. abony : O-1, 4, 5, 12) with group C3 recipients (S. emek : O-(8), 20), loss of O-20 from the recipients appeared in some of the recombinants which had received leu+, pro+, nic+, trp+ or lys+ marker of the group B donor. When another crosses were made between group C3 (S. emek: O-(8), 20) donor strain and recipient strains that had been isolated as a his+ and O-(8) positive recombinat from a cross between group C3 (S. emek : O-(8), 20) donor and a group B (S. paratyphi B var. odense : O-1, 4, 12) recipient, some of pro+ or nic+ recombinants in the crosses received the O-20 gene from the group C3 donor strain. These results suggest that the determinant of somatic antigen 20 was fouud to be closely linked to the pro and nic gene.
5. An Hfr strain of group B (S. abony : O-1, 4, 5, 12) was crossed with an F-strain of group C2 (S. newport var. puerto-rico : O-6, 8) or group C3 (S. emek : O-(8), 20). When recombinants with his locus from the donor were selected, most of them differed serologically from both of parents and formed semirough forms. These semirough recombinants were intermediate between S and R forms giving smooth-looking colonies, growing with deposit in broth, being unstable in saline suspension, and possessing the specificities 4 and 12, or 4, 5 and 12.
