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Biodeterioration of cultural heritage

A large number of caves containing prehistoric paintings ( Altamira Cave of the Bats, ...) have been closed to public visits to avoid damaging them. Despite the darkness and lack of nutrients from the environment, microorganisms can grow. The combination of carbon dioxide produced by the visitors and the microbes living on the surface of the rock lead to the degradation of paintings. In a first phase sought to avoid such degradation by using chemical biocides but these proved to be much more aggressive against the paintings against microorganisms. It was observed that the first stage of biodeterioration of a painting usually begins with the appearance of a blue-green stain. On this blue-green stain becomes available a biofilm composed of a variety of bacteria and fungi that will attack the paint.

Recently, the European Community has initiated a project that aims to prevent degradation and allow resumption of visits. There several research groups and each has developed a specific strategy to solve the problem. Here we describe the two most promising in terms of its preliminary findings and has failed:

• Strategy A: Lighting the caves with a blue-green light. It was observed that avoids the appearance of spots of the same color and therefore no subsequent biofilm develops.

• Strategy B: Use of synthetic siderophores. Siderophores are molecules for iron chelators. This strategy is used both in the initial stages of biofilm formation, as in the more advanced. It is observed reduced biofilm growth and even their disappearance.

• Strategy C: Use of specific antibiotics. The use of fungicides, bactericides or only attacked a certain group of microorganisms (antibiotics against Gram + or against Gram -) decreases the population of these microorganisms in the biofilm. However, the treatment does not appear to be effective or even initially, it is not observed any decrease in the growth of biofilm during treatment. To make matters worse, in the long term appear microorganisms resistant to these compounds, so that the treatment stops be fully realizable.

Questions:

1. What kind of organisms are affected by the strategy A?


2. Considering the answer to question 1, explain why they are the first organisms in the biofilm and how can these organisms live and reproduce in an environment like a dark cavern


3. Why is treatment with antibiotics ineffective even initially?


4. Why synthetic siderophores are effective in inhibiting the growth of the biofilm?


5. you show microorganisms resistant to siderophores?