title: Encapsulation and mouse-virulence of Serratia marcescens strain SM-1 and its variants in relation to colonial morphology.
abstract: With the addition to a soft-agar medium of rabbit anti-flagella serum inhibiting mobility, strain SM-1 of Serratia marcescens produced single colonies. Strain SM-1 and its variants A and B exhibited three kinds of colonial form. The parent strain showing extra large round-type growth in the medium had the highest cell volume index and mouse virulence, and a large capsule was seen on electron microscopy. An intermediate cell volume index and a remarkably lower mouse virulence were observed with variant A, which exhibited diffuse-type growth in the medium, although no definite extracellular feature was shown. The variant B, showing compact-type growth in the medium, represented the lowest cell volume index, mouse avirulence and was not encapsulated. Mouse virulence of the parent strain was assumed to be related to encapsulation which protects against phagocytosis.
mesh_terms: D000362:Agar; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D003470:Culture Media; D005407:Flagella / Q000276:immunology; D006801:Humans; D051379:Mice; D010529:Peritoneal Cavity / Q000382:microbiology; D010587:Phagocytosis; D011817:Rabbits; D012475:Salmonella / Q000276:immunology; D012706:Serratia marcescens / Q000254:growth & development / Q000472:pathogenicity* / Q000648:ultrastructure; D014774:Virulence
chemical_list: D000942:Antigens, Bacterial; D003470:Culture Media; D000362:Agar