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Candida albicans was examined for a glucose effect and showed typical diauxic growth on a mixture of glucose and mannitol, in which mannitol utilization occurred only after exhaustion of glucose. The activity of NAD-linked mannitol dehydrogenase was very low while glucose was present in the medium, but started to increase after consumption of glucose. This increase in activity was fully prevented by trichodermin, an inhibitor of protein synthesis. The uptake of mannitol was detected in the cells grown on mannitol, but not in those grown on glucose with or without mannitol. Mannitol uptake by mannitol-grown cells was not affected by the presence of glucose (0.2 g l-1). These findings indicate that in C. albicans glucose represses the inducible syntheses of mannitol dehydrogenase and a mannitol transport system, and that the involvement of inducer exclusion in this effect is unlikely. Fructose, and to lesser extents galactose, mannose and sucrose, also exhibited similar effects on mannitol metabolism. No correlation was found between the intracellular cyclic AMP levels and the glucose effect.
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PMID:Regulation of mannitol catabolism in Candida albicans: evidence for cyclic AMP-independent glucose effect. 301 28

Cottonseed storage lipids (primarily triglycerides), in either crude or refined form, were found to support growth and aflatoxin B(1) production by Aspergillus flavus. When lipids were removed from ground whole cottonseed by petroleum ether extraction, aflatoxin production dropped by more than 800-fold. Reconstitution of the lipid-extracted ground whole seed with a crude preparation of cottonseed lipids restored aflatoxin production to the previous levels. Fungal utilization of the three major cottonseed reserve materials, raffinose, triglycerides (refined cottonseed oil), and cottonseed storage protein, was monitored in vitro over a 7 day fermentation period. The fermentation medium contained the reserve compounds in proportions approximating those found in mature cottonseed. A. flavus rapidly converted raffinose to fructose and melibiose, presumably by action of invertase, and then hydrolyzed the melibiose. These simple sugars apparently supported initial growth and aflatoxin B(1) production. Raffinose and the resulting melibiose were nearly exhausted by day 2. Fungal hydrolysis of triglycerides began as exhaustion of carbohydrate approached. After day 2, rapid catabolism of the released fatty acids began and coincided with glucose regeneration through gluconeogenesis, which peaked on day 6. The fungus did not preferentially utilize specific fatty acids. A. flavus also produced a number of storage metabolites, including arabitol, erythritol, mannitol, and trehalose. Mannitol was produced in much higher concentrations than the other storage metabolites. Selective use of simple carbohydrates by A. flavus to drive aflatoxin production may suggest strategies for reducing vulnerability of cottonseed to aflatoxin contamination.
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PMID:Influence of lipids with and without other cottonseed reserve materials on aflatoxin B(1) production by Aspergillus flavus. 1095 58