Microbial diversity on a marble monument: a case study

Abstract

In the presented case study, ascomycete fungi and green algae on a marble monument were identified by comparisons of the 18S rRNA gene sequences, which were obtained from DNA either from environmental samples or from enrichment cultures. The organisms were found to be responsible for either black or green surface coverings on different areas of the monument surface. Most fungi were related to plant-inhabiting genera, corresponding to a heavy soiling of the marble surface with honeydew. Whereas green algae of the genera Stichococcus, Chloroidium and Apatococcus were found to be dominant in all samples, isolates of two additional genera were recovered only from enrichment cultures. A reference strain of Apatococcus lobatus and an isolate of Prasiolopsis sp. were investigated with respect to putative surface adhesive structures of the cell envelope. The Prasiolopsis cell walls were covered with a thin adhesive exopolysaccharide layer involved in biofilm formation.

Cryptogam covers on sepulchral monuments and re-colonization of a marble surface after cleaning

“…Adaptations against desiccation and UV irradiation like thick cell walls, mucilage sheaths and Mycosporinelike amino acids (MAAS) are common for aerophytic algae (Karsten et al 2005a, b). The occurrence of the trebouxiophyceaen genera Apatococcus, Desmococcus, Stichococcus, Diplosphaera and Trebouxia on stone substrates is well known (Hallmann et al 2011a;Ragon et al 2012). On the 98 % similarity level two OTUs of Apatococcus were detected; the phylogenetic analysis confirmed two distinct groups (cf.…”

“…Colonization of monuments, including marble sculptures, has been already documented in various studies (e.g., Albertano and Urzì 1999;Ortega-Calvo et al 1995;Lamenti et al 2000;Gorbushina et al 2002;Hallmann et al 2011a). In the case presented here, the surface of the marble sculpture was affected by biodeterioration in two different ways.…”

“…In addition, Stichococcus is an ubiquitous and rapid colonizer known from nitrogen rich sites (Ettl and Gärtner 1995). Since the monument is situated under a tree, bird droppings (Hallmann et al 2011a) may contribute to favorable conditions for Stichococcus. Generally, these photosynthetic microorganisms cause staining by photosynthetic pigments and may be involved in stone decay by secretion of organic acids and indirectly by supporting growth of other microorganisms like fungi and bacteria (Ariño et al 1997;Polo et al 2010).…”

“…Black fungi are frequently found in conjunction with honeydew coverings: Typically, honeydew is secreted by plant-sucking aphids and scale insects (e.g., Auclair 1963). When the plant is massively infested by these insects, the resulting honeydew coverings of surfaces located underneath the plant are colonized by black fungi (Hallmann et al 2011a). The investigated marble sculpture was situated under a tree, which causes a favorable microclimate (protection against high irradiation and evaporation; e. g. Weber et al 2007) and provides nutrients as honeydew, dead plant material and bird droppings for microbial growth.…”

“…All these microorganisms may be involved in biodeterioration, e.g., biopitting by penetration of fungi in the material surface but also as staining caused by algae and black pigmented fungi (Sterflinger and Krumbein 1997;McNamara et al 2006;Polo et al 2010 and references therein). A multitude of studies documented the deterioration of marble monuments and building facades by weathering, pollution and microbial communities (Gromov 1963;Lamenti et al 2000;Gorbushina et al 2002;Moropoulou et al 2002;Cappitelli et al 2007;Weber et al 2007;Sert and Sterflinger 2010;Hallmann et al 2011a).…”