Evolution of Fusarium graminearum A3/5 grown in a glucose-limited chemostat culture at a slow dilution rate.
The evolution of Fusarium graminearum A3/5 grown in a glucose-limited chemostat at a dilution rate of 0.05 h-1 (doubling time of 13.9 h) was followed for 957 h or 69 generations. Periodic selection of advantageous mutants was monitored in the culture by determining increases and decreases in the concentration of cycloheximide-resistant macroconidia in the population. Six peaks in the concentration of cycloheximide-resistant macroconidia were observed representing five adaptive changes in the population; on average, an adaptive change occurred once every 148 +/- 22 h (mean +/- SE). The selection coefficient of strains present at the start of each increase in the concentration of cycloheximide-resistant macroconidia (i.e. after the establishment of a new advantageous strain) was determined relative to A3/5 and was found to increase progressively with time. When grown at a dilution rate of 0.05 h-1, the strain (A28-S) isolated from the last adaptive peak had a selection coefficient of 0.023 h-1 relative to A3/5, but A28-S lost its selective advantage when grown at a dilution rate of about 0.11 h-1 and was at a selective disadvantage when grown at a dilution rate higher than 0.11 h-1. The Km value (12 +/- 5 microM) for uptake of glucose by A28-S was significantly lower than that for A3/5. The spontaneous mutation rate from cycloheximide sensitivity to cycloheximide resistance was estimated to be 1.8 (+/- 0.2) x 10(-6) h-1 or 2.5 x 10(-5) generation.(ABSTRACT TRUNCATED AT 250 WORDS)
Wiebe
M G
MG
School of Biological Sciences, University of Manchester, UK.
Robson
G D
GD
Oliver
S G
SG
Trinci
A P
AP
D000222:Adaptation, Physiological; D005075:Biological Evolution; D003513:Cycloheximide / Q000494:pharmacology; D004352:Drug Resistance, Microbial / Q000235:genetics; D005670:Fusarium / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D005947:Glucose / Q000378:metabolism*; D008828:Microbiological Techniques; D016296:Mutagenesis; D012641:Selection, Genetic; D013172:Spores, Fungal
D003513:Cycloheximide; D005947:Glucose