title: A new episomic element controlling fermentative metabolism and excretion of amino acids by Citrobacter intermedium C3.
abstract: Glutamate excretion by colonies of Citrobacter intermedium C3 was detected by using the auxotrophic strain Leuconostoc mesenteroides P-60. A constant ratio of strain C3 colonies did not excrete glutamate. These colonies were subcultured, and colonial analysis of their descendants established that the change from non-excretor to excretor (Sg(-) --> Sg(+)) is a spontaneous and random process with occurs at a high rate, and that an equilibrium state results from the back-transition Sg(+) --> Sg(-) in large populations. Acridine orange, ethidium bromide, and shaking have a strong influence on Sg(+)-to-Sg(-) interconversion, which suggests that a genetic element like an episome is implicated (S factor). Various auxotrophic mutants of bacterial strain C3 have been cured of the S factor. Strains lacking the S factor (S(-) strains) do not excrete glutamate and lose their fermentative metabolism completely. Consequently, the S factor is different from other extrachromosomal genetic factors whose elimination does not modify central metabolism. The gain of the S factor by infectious transfer has been shown with different C3 auxotrophic mutant strains. Also, the S factor has been transferred to Paracolobactrum intermedium ATCC 11606. These findings suggest that phenotypic changes observed are a consequence of elimination or infectious gain of the S factor, with its autonomous or integrated multiplication.
mesh_terms: D000166:Acridines / Q000494:pharmacology; D003227:Conjugation, Genetic; D004755:Enterobacteriaceae; D004925:Escherichia / Q000378:metabolism*; D004926:Escherichia coli / Q000254:growth & development / Q000528:radiation effects; D004996:Ethidium / Q000494:pharmacology; D005111:Extrachromosomal Inheritance; D005285:Fermentation; D014644:Genetic Variation; D005971:Glutamates / Q000378:metabolism*; D007934:Leuconostoc / Q000378:metabolism; D008242:Lysogeny; D009154:Mutation; D011830:Radiation Effects; D014466:Ultraviolet Rays
chemical_list: D000166:Acridines; D005971:Glutamates; D004996:Ethidium