Bacteria used to bolster ancient buildings

Micro-organisms thriving in polluted urban areas are held largely responsible for the crumbling of cultural heritage sites worldwide. Now, scientists from the University of Portsmouth, England, are looking at ways to reverse the trend and put some of the bacteria to good use.

The team, led by Dr Eric May, is part of Biobrush " short for Bioremediation for Building Restoration of the Urban Stone Heritage - a European initiative coordinated from the United Kingdom that takes a novel approach to conserving European heritage.

The aim is to devise a biotechnology tool based on bioremediation that is safe and environmentally friendly to use. To achieve this, the scientists plan to sequentially link mineralisation processes of desulfurication and denitrification and organic removal to the consolidation phenomenon of bio-calcification.

It has been proved that some micro-organisms use sulphate, nitrate or organic residues to form layers of calcite on mineral surfaces. The project brings together microbiologists, material scientists, conservators and industrial consultants from five European countries.

Working in collaboration with institutions from Italy, Greece, Latvia and Germany, the team at Portsmouth University has specified a number of micro-organisms that are safe and effective to use to destroy mineral salt crusts and organic compounds.

They have also identified other bacteria that can produce biocalcite that helps to consolidate stone materials after the initial course of treatment.

Different treatment combinations are undergoing tests in laboratory conditions as well as on site under the various climatic conditions of northern and southern Europe, and include a medieval castle in Latvia, a town hall in Germany, a cathedral in Italy and an ancient settlement in Greece.

Existing conservation practices such as the application of fixatives and water-repellent coatings are often complicated and occasionally ineffective. Mechanical processes for the removal of crusts can cause the loss of the original surface; physico-chemical cleaning can bring about colour changes in rock.

The innovative technology using bioremediation is expected to be reversible, easily controllable and possibly cheaper than current practice. Early in 2005, at the end of the four-year research program, the consortium will also present a technology implementation plan, helping partners in industry and commerce to put the results of the Biobrush research to large-scale practical use.