Release of glucose by 7Vay?oc tspec. isolated from the lichen

Cultured JV<M?oc spec, from Pe///gero excreted in the light between 1% and 3.4% of fixed "CO, into the medium, <0.8% as glucose. A several-fold increase in the rate of release was caused by addition of carbony! cyanide p-trifluoromethoxyphenylhydrazone (FCCP) in the dark, the major component released being glucose. The amount of glucose excreted in the presence of FCCP exceeded the pool of intracellular glucose + glucose 6-phosphate by far, suggesting a glucan as a precursor. A glucan — identified enzymatically with amyloglucosidase — was the main assimilation product which was degraded during excretion of glucose in the dark in the presence of FCCP. Of the free-living cyanobacteria, Nayfoc/?M/7cr(/brwe also showed glucose release whereas TVasfoc fnnscorMfM did not. It is concluded that (i) the symbiotic JVasfoc spec, can excrete glucose in the absence of the fungal partner, (ii) this release is a passive process being fed by a glucan and (iii) glucose release is not a specific function of symbiotic cyanobacteria.