Microscopic examination of bacteria in Fe(III)-oxide deposited from ground water.

Ochreous sludge deposited in the course of aeration of ground water contained an assortment of bacterial forms and structures which were investigated by light microscopy, scanning electron microscopy, and transmission electron microscopy. Bacterial structures were often covered by iron deposition which could be removed by acidification of the samples. Sulfuric acid treatment was consistently better than hydrochloric acid to dissolve iron without a considerable damage to the bacterial cells. Partial dissolution of amorphous ferric iron was achieved by acidifying the samples with oxalic acid or citric acid prior to the preparation for electron microscopy.