Abstract
Biofilm on the sandstone substrata of the bridge 'Brankov most' and on the granite substrata of the 'Monument of the Unknown Hero' contains a complex consortia of cyanobacteria, algae, and fungi. Coccoid and filamentous cyanobacteria, green algae and diatoms make up the photosynthetic part of the biofilm while hyphal fragments, chlamydospores, fruiting bodies and spores take part as fungal components. These structures make a dense layer by intertwining and overlapping the stone surface. Five cyanobacterial, 11 algal and 23 fungal taxa were found. The interaction of the biofilm's constituents results in the bioweathering of the stone substrata through mechanical penetration, acid corrosion and the production of secondary mycogenic biominerals. .
Highlights
During the recent decades there has been a general concern about the deterioration of historic buildings
The photosynthetic organisms of the biofilm were comprised of 5 taxa of cyanobacteria, 5 taxa of green algae and 6 diatom taxa (Table 1)
The most abundant biofilm-forming cyanobacteria on the sandstone substrata was coccoid Gloeocapsa novacekii while the only cyanobacteria detected on the granite substrata was a filamentous species belong to the Leptolyngbia genus which included subaerophytic species, inhabiting different types of wet stone surfaces
Summary
During the recent decades there has been a general concern about the deterioration of historic buildings. Microorganisms from all five kingdoms of the living world can colonize stone surfaces depending on stonebioreceptivity and form a microbial sub-aerial community biofilm. Bioreceptivity is a term which indicates the potential of a material such as stone for colonization by one or more groups of living organisms without necessarily undergoing any biodeterioration (Prieto & Silva, 2005). The microbial colonization of stones depends on environmental factors such as water availability, pH, climatic exposure, nutrient sources, and on petrologic parameters, such as mineral composition porosity and permeability of the rock material (Warscheid & Braams, 2000). The bioreceptivity of stone depends on its structure and chemical composition, while the intensity of the microbial contamination is caused by the climatic conditions and the anthropogenic eutrophication of the atmosphere (Prieto & Silva, 2005). It has been shown that the very low nutrient requirements of some rock inhabiting heterotrophic microorganisms may be fulfilled by remains of polluted air and rain or animal remains and secretion (Suihko et al, 2007)
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