Glucose uptake in germinating Aspergillus nidulans conidia: involvement of the creA and sorA genes.

D-Glucose uptake in germinating wild-type Aspergillus nidulans conidia is an energy-requiring process mediated by at least two transport systems of differing affinities for glucose: a low-affinity system (K(m) approximately 1.4 mM) and a high-affinity system (K(m) approximately 16 micro M). The low-affinity system is inducible by glucose; the high-affinity system is subject to glucose repression effected by the carbon catabolite repressor CreA and is absent in sorA3 mutant conidia, which exhibit resistance to L-sorbose toxicity. An intermediate-affinity system (K(m) approximately 400 micro M) is present in sorA3 conidia germinating in derepressing conditions. creA derepressed mutants show enhanced sensitivity to L-sorbose. The high-affinity uptake system appears to be responsible for the uptake of this toxic sugar.