microbiology, Vol 142, 525-532, Copyright © 1996 by Society for General Microbiology
How do highly branched (colonial) mutants of Fusarium graminearum A3/5 arise during Quorn myco-protein fermentations?
MG Wiebe, ML Blakebrough, SH Craig, GD Robson and AP Trinci
School of Biological Sciences, University of Manchester, UK.
Chlorate-resistant, highly branched (colonial) mutants and auxotrophic
mutants were used to study the nuclear distribution, morphology and growth
of heterokaryons of the Quorn myco-protein fungus, Fusarium graminearum
A3/5. The results showed that for several complementary homokaryons, even a
strong selective pressure was insufficient to maintain heterokaryons in a
'balanced' condition (i.e. exhibiting a wild-type or near wild-type
phenotype). Furthermore, the margins of heterokaryotic colonies generally
contained nuclei from only one of the parental homokaryons, indicating
imperfect nuclear mixing within the mycelium. These observations suggest
that recessive, colonial mutants may appear during Quorn myco-protein
production following shear-induced separation of hyphal fragments which
contain a sufficiently high ratio of colonial:wild-type nuclei for the
colonial phenotype to be expressed.
