| Popis: |
SummaryFollowing prolonged incubation of originally smooth Brucella abortus broth cultures, relatively avirulent nonsmooth variants established themselves but were eventually replaced by a smooth type, labelled S′, in turn replaced later by still another smooth type, labelled dS. These three smooth types were found to be similar in many characteristics, including virulence, but differed significantly in their resistance to alanine, an inhibitory metabolite which accumulates in the culture fluid. These differences in alanine resistance permitted the S′ and dS mutants to establish themselves at periods when alanine levels of the cultures were high. Therefore, what superficially appeared to be an establishment of reverse mutants actually involved the establishment of novel mutants which simulated the original smooth type in many characteristics. |
