Microbial Methyketone formation is strongly favored under conditions in which mold growth is constrained for sample, during sporulation. Perhaps methylketone synthesis is induced when celular levels of coenzyme A become limited , thereby reducing 3-ketoacyl-CoA thaiolase activity. Curiously, fungi do not produce Methyketones from long-chain fatty acids even when growth is restricted. Instead, the B-oxidation cycle proceeds to completion. Presumably, such microbial cells contain more than one system for dealing with fatty acids of different chain lengths.