ABSTRACT
Vibrio cholerae O1 bacteria harvested directly from ligated or nonligated intestines of rabbits with experimental cholera expressed at least 7 to 8 novel, in vivo-specific cell envelope (env) proteins that were not found on vibrios after in vitro culture in various ordinary liquid media. At the same time, several of the env proteins ordinarily expressed in vitro had disappeared or become much reduced. The infection-induced novel env protein were immunogenic. In immunoblot analyses, antisera raised against in vivo-grown vibrios and then absorbed with in vitro-grown bacteria of the same strain specifically stained at least eight infection-induced antigens ranging from 62 to approximately 200 kilodaltons; absorption with washed in vivo-grown bacteria, on the other hand, removed the antibodies reacting with these antigens, indicating that the antigens were present on the bacterial cell surface. Conversely, antiserum against in vitro-grown bacteria reacted with several env antigens in in vitro-grown bacteria that were missing in the infection-derived vibrios. These adaptational changes were strikingly similar for different strains of cholera vibrios of both classical and El Tor biotypes. Most of the in vivo-specific proteins (with apparent molecular masses of approximately 200, approximately 150, approximately 140, 92, 68, 62, 43, and 29 kilodaltons) were not induced during cultivation of bacteria in iron-depleted medium and are probably not related to the iron-regulated env proteins known to be involved in iron transport systems.
