Lysogenization of Salmonella choleraesuis by phage 14 increases average length of O-antigen chains, serum resistance and intraperitoneal mouse virulence.
Three clones from a strain of Salmonella choleraesuis (serogroup C1) were lysogenized with phage 14 (P14) which converts the O-antigen of serogroup C1 salmonellae from O-6,7 to O-6,7,14. The lysogens were compared with their parental non-lysogenic clones with respect to the following properties: average length of O-antigen polysaccharide chains, sensitivity to normal human serum, and mouse-virulence. SDS-polyacrylamide gel electrophoresis of lipopolysaccharides extracted from these bacteria showed that samples from lysogens consisted mainly of long-chained molecules whereas those from non-lysogens contained mainly short-chained molecules. The O-antigen polysaccharide from a lysogen was estimated by chemical analysis to be six times as long as that from a non-lysogen. Lysogens were serum-resistant whereas non-lysogens were serum-sensitive. About 10 times more colony forming units of a lysogen than of a non-lysogen were recovered from the livers and spleens of mice on day 1 and 3 after intraperitoneal inoculation of equal doses. By comparison with S. choleraesuis, lysogenization of S. typhimurium with phage P22 or phage A4 did not affect the chain-length distribution of O-antigen polysaccharide. Our data suggest that phage 14-coded determinants increase efficiency of O-antigen biosynthesis in S. choleraesuis leading to increase in average length of O-polysaccharide chains. Increased serum resistance and mouse virulence are logical consequences of increase in average length of O-polysaccharide chains and represent phage-conferred selective advantage not previously described in Salmonella.
Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305.
N A
NA
Nnalue
S
S
Newton
B A
BA
Stocker
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001435:Bacteriophages / Q000276:immunology*; D002240:Carbohydrate Sequence; D003720:Densitometry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008070:Lipopolysaccharides / Q000032:analysis; D008099:Liver / Q000382:microbiology; D008242:Lysogeny / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D019081:O Antigens; D012475:Salmonella / Q000472:pathogenicity*; D013154:Spleen / Q000382:microbiology; D014774:Virulence / Q000276:immunology
D000942:Antigens, Bacterial; D008070:Lipopolysaccharides; D019081:O Antigens