Fifteen bacterial strains and four molds capable of growth on n-butane were isolated and partially classified. The bacteria were mostly Arthrobacter sp. and Brevibacterium sp.; among the molds, Penicillium nigricans, Allescheria boydii, and Graphium cumeiferum were identified, while the remaining mold had the appearance of Gliocladium, but was not firmly identified. Although able to grow on other alkanes and orthodox media, the bacterial isolates could not use methane. Growth rates on n-butane were unaffected by varying air or substrate partial pressures in the range of 10–90% atmosphere. High partial pressure of oxygen was inhibitory to most bacterial isolates, the degree of inhibition varying widely, however. Growth rates on n-butanol and on glucose were significantly higher than those on n-butane. Among the molds, only the Graphium would grow well in submerged, shaking culture.

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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.

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