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Nutrient‐dependent selection of morphological mutants of Fusarium graminearum A3/5 isolated from long‐term continuous flow cultures
Author(s) -
Wiebe Marilyn G.,
Robson Geoffrey D.,
Cunliffe Bryan,
Trinci Anthony P. J.,
Oliver Stephen G.
Publication year - 1992
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260401007
Subject(s) - maltose , dilution , fructose , ammonium , biology , continuous flow , chemically defined medium , food science , sucrose , biochemistry , botany , chemistry , in vitro , organic chemistry , physics , mechanics , thermodynamics
Highly branched (colonial) mutants (MC1‐1‐, CC1‐1, and C106) of Fusarium graminearum A3/5 were each grown with the parental strain (A3/5) in continuous flow cultures at high and low dilution rates using a variety of nutrient limitations. MC1‐1 replaced A3/5 in all nutrient‐limited cultures tested (glucose‐, Mg 2+ ‐, ammonium‐, and sulphate‐limited cultures), suggesting that it has a higher maximum specific growh rate than A3/5. Compared with A3/5, C106 was positively selected for in Mg 2+ ‐limited cultures and its selection coefficient was higher at low than at high dilution rates, suggesting that, compared with A3/5, it has a reduced saturation constant ( K s ) for Mg 2+ . However, in batch culture, C106 and A3/5 had the same (15 μ M ) appaent K s value for Mg 2+ . C106 was replaced (negative selection coefficient) by A3/5 in gluose‐, ammonium‐, and phsophate‐limited continuous flow cultures, but was neither at an advantage nor a disadvantage (i.e., it behaved as a neutral mutation) in sulphate‐limited cultures. CC1‐1 replaced A3/5 when they were grown together in glucose‐, maltose‐, or ribose‐limited continuous flow cultures, but not in fructose‐, xylose‐, ammonium‐, or phsophate‐limited cultures. Because A3/5 and CC1‐1 had similar K m values (30 μ M ) for glucose, and because the selective advantage of CC1‐1 was maintained in maltose‐limited cultures (maltose was not hydrolyzed extracellularly), it was concluded that the selective advantage of CC1‐1 did not result from it having a lower K s for glucose than the parental strain. Rather, the data suggested that the activity of phosphoketopentoepimerase may be altered by the CC1‐1 mutation. © 1992 John Wiley & Sons, Inc.