Biodiversity of cyanobacteria and green algae on monuments in the Mediterranean Basin: an overview

Abstract

The presence and deteriorating action of micro-organisms on monuments and stone works of art have received considerable attention in the last few years. Knowledge of the microbial populations living on stone materials is the starting point for successful conservation treatment and control. This paper reviews the literature on cyanobacteria and chlorophyta that cause deterioration of stone cultural heritage (outdoor monuments and stone works of art) in European countries of the Mediterranean Basin. Some 45 case studies from 32 scientific papers published between 1976 and 2009 were analysed. Six lithotypes were considered: marble, limestone, travertine, dolomite, sandstone and granite. A wide range of stone monuments in the Mediterranean Basin support considerable colonization of cyanobacteria and chlorophyta, showing notable biodiversity. About 172 taxa have been described by different authors, including 37 genera of cyanobacteria and 48 genera of chlorophyta. The most widespread and commonly reported taxa on the stone cultural heritage in the Mediterranean Basin are, among cyanobacteria, Gloeocapsa, Phormidium and Chroococcus and, among chlorophyta, Chlorella, Stichococcus and Chlorococcum. The results suggest that cyanobacteria and chlorophyta colonize a wide variety of substrata and that this is related primarily to the physical characteristics of the stone surface, microclimate and environmental conditions and secondarily to the lithotype. IntroductionStone monuments, statues and historic buildings are exposed to the effects of physical, chemical and biological deteriorating factors. This review will focus on the damage caused by micro-organisms, in a process referred to as biodeterioration. Stone works of art can be colonized by different groups of micro-organisms, including bacteria, cyanobacteria, algae and fungi. Microbial populations present in a stone substratum are usually the result of successive colonization by different micro-organisms that has taken place over several years. It is a process that relies upon the capacity of a substratum to provide a protective niche on which micro-organisms can develop. According to several authors, cyanobacteria and chlorophyta (green algae) are considered the pioneering inhabitants in the colonization of stone (Ortega-Calvo et al., 1991;Tiano et al., 1995; Cecchi et al., 2000;Lamenti et al., 2000;Tomaselli et al., 2000b;Crispim & Gaylarde, 2005). Due to their photoautotrophic nature, these micro-organisms develop easily on stone surfaces, giving rise to coloured patinas and incrustations ( Fig. 1) (Tomaselli et al., 2000b). Identifying the micro-organisms involved in biodeterioration is one of the most important steps in the study of the microbial ecology of monumental stones. It can help us to understand the microbial biodiversity, the phases of colonization and the relationship among populations on the surfaces and between micro-organisms and substrata.Here we review the occurrence of cyanobacteria and green algae identified on stone monuments, statues and histo...

Biocidal effect of lichen secondary metabolites against rock-dwelling microcolonial fungi, cyanobacteria and green algae

“…Although the blackening of buildings and monuments can be also related to anthropogenic causes, as the deposition of gases and particles or sulphation mechanisms (Prieto et al, 2007), microorganisms as dematiaceous meristematic fungi, including microcolonial fungi (MCF), filamentous and coccoid cyanobacteria and, subordinately, green algae are also recognized as common agents of such threat to conservation (Gorbushina and Broughton, 2009;Macedo et al, 2009;Sterflinger, 2010). These organisms determine anaesthetic discoloration because of their dark pigments (Scheerer et al, 2009) and are often associated to physical and chemical deterioration processes because of their mechanical penetration and the release of acidic and chelating compounds (Macedo et al, 2009;Sterflinger, 2010;Favero-Longo et al, 2011).…”

Screening and partial purification of photoprotective pigment scytonemin from cyanobacterial crusts dwelling on the historical monuments in and around Varanasi, India

“…Pigmentation may also change in response to environmental factors such as light quality, light intensity, temperature, nutrient availability and the age of cells. 40 The cyanobacterial sheath has been suggested to be associated with cellular resistance against various environmental stresses and presence of UV-absorbing pigments, extrapolysaccharides (EPS) and water stress protein (Wsp) have been reported to be present in the cyanobacterial sheath of various genera. 41 In the present study, the UVabsorbing pigment, scytonemin from cyanobacterial crusts was screened and partially purified through HPLC.…”

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

“…However, Trebouxia has been frequently described in terrestrial habitats even when identifiable lichens were absent (Gärt-ner 1994; Macedo et al 2009). Furthermore, soredia (asexual reproductive structures) were observed by SEM on the surface of a lichen thallus (Fig.…”