RT Journal Article SR Electronic(1) A1 Tsang, E. W. T. A1 Grootwassink, J. W. D.YR 1988 T1 Extraordinarily Rapid Appearance of a β-Fructofuranosidase (Exo-inulase)-hyperproducing Mutant in Continuous Culture of Kluyveromyces fragilis JF Microbiology, VO 134 IS 3 SP 679 OP 688 DO https://doi.org/10.1099/00221287-134-3-679 PB Microbiology Society, SN 1465-2080, AB A wild-type strain of the yeast Kluyveromyces fragilis was grown in continuous culture on inulin-, fructose- and glucose-limited media. In the presence of organic nitrogen, all three carbon sources supported an extremely rapid changeover to a homogeneous mutant cell population that exhibited hyperproduction of β-fructofuranosidase (exo-inulase). The non-specific role of the carbon substrate in the takeover suggested co-regulation of inulase synthesis and early glycolytic pathway enzymes such as hexokinase, resulting in gratuitous hyperproduction of inulase. The rate of mutant appearance increased linearly with a decrease in dilution rate as well as carbon/nitrogen ratio, implying that the responsible forces were related to the residual concentration of the limiting carbon substrate. Under optimum conditions, mutant cells were detected within only 40 h (2·9 generations) from the start of continuous culture, at least 6·5 times faster than predicted. The maximum rate of displacement was as high as 54% per generation, or more than 12 times greater than predicted from the differential growth rate between the wild-type and mutant strain. These extraordinarily rapid takeovers point to a very fast and ongoing genetic change triggered by growth under severe stress., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-134-3-679