Chemoorganotrophic bacteria, quantitatively determined and isolated from the uppermost layers of sandstones of several monuments within Germany under copiotrophic and oligotrophic conditions, were analyzed with regard to their nutrient requirements, their capability to produce organic acids as well as their possible influence on the oxidation of manganese and iron. It was shown that most of the isolated chemoorganotrophic bacteria use a wide range of different carbohydrates, amino acids, fatty acids and hydrocarbons. About 40% of the strains analyzed were shown to be potential acid producers, whereas the capability of manganese and iron oxidation is only sporadically found in chemoorganotrophic bacteria living on rock. The consequences of these findings for the microbial attack and deterioration of sandstones are discussed.