An alternative spelling of eukaryotes: organisms whose cells contain a nucleus and other membrane-bound organelles. They include the yeasts and moulds central to food fermentation and spoilage, as well as plants and animals, in contrast to the prokaryotic bacteria and archaea. In food systems, eukaryotic yeasts (Saccharomyces) drive alcoholic fermentation and bread leavening, while eukaryotic moulds both ripen cheeses and spoil stored products. Their larger genomes and organelle-based metabolism make them targets of antifungal preservatives such as natamycin, which binds ergosterol in fungal membranes.