ALGAE AND BACTERIA ON HISTORIC MONUMENTS AT ALCALA-DE-HENARES, SPAIN

Bacteria belonging to the genera Bacillus, Micrococcus and Thiobacillu s, yeast and microalgae of the Apatococcus genus colonize the building of two monuments at Alcala de Henares (Spain). In highly altered zone s, polymicrobial communities were observed, mainly beneath the surface of the crusts, which demonstrated that rock surfaces are good substra tes and offer possibilities for interaction among several types of pop ulations. Microbial activity in surface layers of the stone was reveal ed by means of the TTC (triphenyltetrazolium chloride) test. With SEM (scanning electron microscopy), the weathering of the substrate was ob served, as well as the presence of pollution particles and microbial s tructures. (C) 1997 Elsevier Science Ltd. All rights reserved.