Recolonization of mortars by endolithic organisms on the walls of San Roque church in Campeche (Mexico): A case of tertiary bioreceptivity

San Roque church (Campeche, Mexico) was built at the end of the 17th century with a micritic limestone and lime mortar in baroque style. In 2005 the church exhibited heavy biodeterioration associated with the development of extensive dark green phototrophic-based biofilms. Several cyanobacteria belonging to the order Chroococcales and lichenized fungi (Toninia nordlandica, Lobaria quercizans, Lecanora subcarnea, Cystocoleus ebeneus) were predominant in the dark biofilm samples, as revealed by DNA-based molecular techniques. In 2009, a cleaning and restoration intervention was adopted; however, after few months, microbial recolonization started to be noticeable on the painted church walls, representing an early phototrophic-based recolonization. According to molecular analysis, scanning electron microscopy observations and digital image analysis of cross sections, new phototrophic-based colonization, composed of cyanobacteria and bryophytes, developed mainly beneath the restored mortars. The intrinsic properties of the mortars, the tropical climate of Campeche and the absence of a biocide treatment in the restoration protocol influenced the recolonization of the church façades and enhanced the overall rate of deterioration in a short-term period.This work was carried out under the Mexico Research Project “Influencia del entorno urbano en los procesos de degradación de edificios militares y religiosos de la época colonial en la ciudad de Campeche” (FOMIX CONACYT, CAMP2005-C01-028) and Junta de Andalucía through funding to research team RMN 201. This is a TCP CSD2007-00058 paper. SC benefited from a postdoctoral fellowship from the Spanish Ministry of Science and Innovation, Juan de la Cierva research program. This work was also supported by Fundação para a Ciência e a Tecnologia (Portugal) with a postdoctoral grant to AZM (SFRH/BPD/63836/2009)