Biomass and organic acids in sandstone of a weathering building: Production by bacterial and fungal isolates.

Ten fungal and nine bacterial strains were isolated from a weathering sandstone building. Their growth, organic acid production, and acidification capacity were assessed in culture under nutritional conditions similar to those in situ. Biomass (10-50 nmol phospholipid-PO4g(-1)) within the rock was small compared to soils. The isolated organisms were able to produce high amounts of those acids found in the sandstone, but acid production did not cause a drastic reduction in culture pH. It is suggested that the importance of acidification in microbial degradation of sandstone has been overestimated and that, under in situ pH and nutritional conditions, cation chelation by microbially produced organic acid anions may be more relevant to the weathering process.