Permeability and metabolism of lactose in Neurospora crassa.

Lester, G. (Worcester Foundation for Experimental Biology, Shrewsbury, Mass.), D. Azzena, and O. Hechter. Permeability and metabolism of lactose in Neurospora crassa. J. Bacteriol. 84:217-227. 1962.-Germinated conidia of Neurospora crassa suspended in buffer take up lactose, and this uptake can be attributed to the intracellular accumulation and to the metabolism of lactose. The former process predominates initially, and the latter after a few hours of incubation. The accumulation of lactose appears to be mediated by a very specific transport system, which can bring about intracellular concentrations that greatly exceed the external concentration of lactose. Both the influx and efflux of lactose appear to be dependent on metabolic energy, since azide and low temperature inhibit these events. The steroid hormone 11-deoxycorticosterone also reduces the uptake and prevents the accumulation of lactose. The metabolism of lactose was clearly demonstrated, but the pathway(s) of metabolism was not defined. The amount of beta-galactosidase activity extractable from the cells was insufficient to be solely responsible for the initial step in lactose metabolism. The present studies are discussed in relationship to ion permeability and lactose metabolism in N. crassa, and to galactoside permeability in Escherichia coli.