Characteristic cytoplasmic structures in microorganisms utilizing n-butane and 1-butanol

Intracellular structures were observed in two Arthrobacter spp. and in Candida utilis in media containing n-butane or 1-butanol as the sole source of carbon; these structures were absent in the same organisms grown in the presence of glucose. These substrate-specific structures consisted of electron-dense bodies nearly surrounded by a round electron-transparent area, and connected to the main cytoplasm by a bridge. These structures may represent sites of hydrocarbon or alcohol oxidation, and the name "oxisome" is proposed for them. The microorganisms contained about 8 times as much iron when growing on n-butane as when growing on glucose, and about 3 to 4.5 times as much when growing on 1-butanol. When one of the Arthrobacter sp. was grown on n-butane in the absence of iron, more diffuse and less structured concentrations of electron-dense particles appeared. Extraction of n-butane-grown cells suggests that the electron transport system is different from other known electron carriers.