Ultracytochemical localization of aldehyde dehydrogenase in Acinetobacter calcoaceticus

A membrane-bound aldehyde dehydrogenase is induced in Acinetobacter calcoaceticus grown on aliphatic hydrocarbons as sole carbon source. This enzyme is NADP-dependent and is able to oxidize medium- and long-chain aliphatic aldehydes to their corresponding fatty acids. Electron micrographs of sectioned alkane-adapted bacteria showed hydrocarbon inclusions in the cytoplasmic matrix. The cytochemical phenazine methosulphate-tetranitro tetrazolium blue capture reaction allowed to localize the activity of the aldehyde dehydrogenase near the surface of these inclusions. At the same location we also found a NADPH tetrazolium-reducing activity.