Our microscopic evaluation indicated that arthrospores were
present, butwere likely only a very small percentage of the total hyphal
phase population harvested for thermal destruction (Fig. 5). Additionally,
zygospores only formwhen two compatible mating pairs of this heterothallic
fungusmeet under the appropriate environmental conditions
(Choppin et al., 1997;Wurtz and Jockusch, 1975). Based on these observations,
it is unlikely that M. circinelloides survived the pasteurization
process and is instead a contaminant that was introduced after thermal
treatment.