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

Abstract 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 facades and enhanced the overall rate of deterioration in a short-term period.