Abstract
During the studies of iron depositing bacteria as found in milk (see preceding paper) and being impressed with the possible relation of these organisms to hard pan formation, some iron hard pans such as abound in certain sections in the state of California were inoculated into the ferric ammonium citrate medium of Harder. 1 After standing two months a precipitate appeared which is typical of the reaction of iron depositing bacteria in this medium. Plates poured with this medium showed colonies of bacteria (bacilli) and actinomyces. Observation of these pans under the microscope disclosed as well some very minute threads which on staining suggested crenothrix. Not all of the pans, however, showed this appearance.
It is recognized that this is hypothetical, but Morrison and Sothers 2 have suggesteld this very thing, although with no apparent evidence to substantiate their suggestion. And recently A. C. Swinnerton 3 states that bacteria “may be important factors in the cementation of sand and gravel materials.”
Work along this line is being continued.
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