Structural features of manganese precipitating bacteria

Studies of biological communities of the past (and their associated activities) are usually dependent upon preservation of fossil material. With bacteria this rarely occurs because of the absence of sufficient fossilizable cellular material. However, some bacteria deposit metabolic products that can, conditions allowing, be preserved indefinitely. In particular, manganese and iron depositing bacteria have the capacity to form preservable microfossils. In order to better understand these microfossils of the past, we have examined present day morphologies of manganese oxidizing bacteria. These bacteria are highly pleomorphic, depending on the growth medium, the age of the culture, and the extent of manganese oxidation. Transmission electron microscopy indicates that manganese may be deposited either intra-or extra-cellularly. The prognosis of the use of morphological information for the interpretation of ancient and modern manganese deposits is discussed.