Environmental Impact on Biopigmentation of Mural Painting

The microclimate monitoring of Humor Monastery, Tismana Monastery and the refectory of Hurezi monastic complex from Romania was performed in order to investigate its effect on the growth of bacteria isolated from infilling mortar. According to the results, microclimate parameters values in Humor Monastery and the refectory of Hurezi monastic complex were similar but specific for each season due to the absence of central heating. Opposite, in Tismana Monastery with central heating, no remarkable differences were noticed during the year. Laboratory results showed that Halobacillus sp., Halobacillus naozhouensis and Nesterenkonia sp. were able to grow in the temperature range between 4 and 37°C with optimum at 28°C, respectively 15°C. The microclimate parameters from all objectives are favorable for carotenoid producing bacteria which developed true pink biofilms very well attached by the original and infilling mortar as well as by pictorial layer, hiding the real color of mural painting. The microbial origin of pink pigmentation on frescoes from Romanian historical monuments was demonstrated.