Legionellosis as an emergent disease

BIODETERIORATION OF HISTORICAL MONUMENTS AND BUILDINGS

INTRODUCTION

The growing concern for the preservation of cultural heritage, such as buildings or historical monuments, has caused a greater interest in the biodeterioration of these by microorganisms. The biodeterioration process can take place in various materials, such as wood, paper, rocks, concrete, metals, paints, plastics and other polymers. These materials can be present in the construction of historical buildings and monuments. This process is caused by microorganisms, mainly cyanobacteria, bacteria and algae (Videla, H. A. et al., 2003); but biodeterioration can also be caused by lichens, heterotrophic bacteria, and fungi (Ascaso et al. 2002).

Image 1:Buildings of cultural heritage showing microbial biofilms. Source: (Crispim C.A., Gaylarde C.C. 2005).

This alteration of the materials produced by microorganisms is very frequent, finding biofilms on any surface with humidity, certain physicochemical characteristics and favorable environmental conditions. In this way characteristic and well-developed ecosystems are formed, the characteristics of the material and the conditions already mentioned (Crispim C.A., Gaylarde C.C. 2005).

The colonization of monuments by microorganisms begins with the accumulation of photoautrophic microorganisms forming visible biofilms on the surface of the material (Danin, A. et al., 1982). Metabolic activity, as well as the growth of these microorganisms, are regulated by parameters such as light or humidity (Monte, M. 1993), and even by the surface type, in case the growth is superficial we find epileptic photoautrophs, while in cases where growth is found in the pores we find endolithic photoautrophs (Friedmann, EI 1984).

PROCESSES AND  INVOLVED MICROORGANISMS

Initially it was believed that the presence of these microorganisms on the material in the form of biofilms only caused aesthetic problems, damaging the surface coloration without causing a direct effect on the deterioration of the materials (Pietrini, A.M. et al., 1985). But they also cause mechanical and structural damage (Krumbein 1972; Bellinzoni et al., 2003).

On the other hand, the climatic conditions and the presence of anthropogenic contamination feed the biodeterioration process, which is characterized by the excretion of corrosive acids, especially in limestone (Jones, D., Wilson, MJ 1985) ; Alkalineolithic attack on silicate minerals (Gaylarde, C.C., Morton, L.H.G. 2002); the uptake and accumulation of sulfur (S) and calcium (Ca) in the cells (Viles, H.A., Moses, C.A. 1996). Therefore, the contamination favors the presence of carbon dioxide (CO₂), and in this way photoautrophic microorganisms that use CO₂ can grow faster. Therefore, these microorganisms can contribute to the breakdown of crystalline structures of rocks such as sandstone, granite, gneiss, limestone, etc. (Fahrig, N. 1991).

So we can say that the most notable microorganisms in biodeterioration are:

Fotolitoautotroph

●  Cyanobacteria and green algae: these groups of microorganisms cause mechanical damage, extend the cracks and mainly cause major aesthetic damage. They are found in rocks where there is light and liquid water or gas (Krumbein 1972; Ortega-Calvo et al., 1991). They form carbonic acid as a result of the reaction between carbon dioxide (CO₂) (respiration product) and water (H₂O) (Doehne, E., Price, C.A. 2010).

Image 2: Biofilm on the surface of a historic building, which shows filamentous dark pigments and cyanobacterial cells. Source: (Crispim C.A., Gaylarde C.C. 2005).

Quimiolitoautotrophs:

●    Sulfur Bacteria: They form calcium sulphate (CaSO₄) for acid attack on rock material (Caneva et al., 1991; Allsopp et al., 2004). Ex: Acidothiobacillus spp.

●    Nitrifying bacteria: they oxidize ammonia (NH₃) by producing nitrates (NO₃-), which react with the calcium carbonate (CaCO₃) of the rocks, giving rise to calcium nitrate (Ca(NO₃)₂), which is soluble ( Mansch, R., Bock, E. 1998). Ex: Nitrosomonas spp. or Nitrobacter spp.

●    Halophilic bacteria: using the crystallized salts of murals and frescoes as a resource (Büdel et al. 2004; Piñar et al., 2009). Ex: Idiomarina spp., Halomonas spp. and Rubrobacter spp.

CONSEQUENCES OF BIODETERIORATION

The majority of engineering, construction and ornamental elements are colonized by microorganisms, mainly fungi, algae and bacteria. These grow quickly and create structures called biofilm, most are natural origin and contain a consortium of microorganisms with different metabolic requirements. As can be seen in table 1, many of them cause different effects on materials and will have different degrees of impact on the material.

 Table 1:The effects of microbial activities on historic buildings   Source: (Gaylarde 2014).

According to (Gaylarde 2014) layers of organic pollutants can act as nutrients for the growth of heterotrophic microorganism ( bacteria and fungi), consequently accelerating both aesthetic and physical.chemical deterioration. Adsorbed contaminants include fatty acid and aromatic hydrocarbons, which modify the nature of the surface of the stone, increased sulfur and nitrogen inputs, such as acid rain, and particulate trace elements can also stimulate microbial growth.

Also salts of organic acids, produced by microbial cells during their normal metabolic processes, can mobilize cations from within the stone, causing degradation. If has been suggested that iron chelating compounds produced by living cells can induce microcracks on the surface of the stone (Gaylarde 2014).

Finally it has been seen as a result of the study on historical buildings, that after extracting different samples from buildings, that biodegradation is not prevented by coating products in stone buildings, biodegradation is not prevented by coating products in stone buildings, they themselves are subject to microbial growth. However hard surfaces, smooth and less porous, such as basalt or varnished stone, are more resistant to microbial colonization, but can still be attacked by various microorganisms.

The resulting biofilms should be removed regularly, using non-abrasive and environmentally safe methods, to reduce the impact of microbial activities (Gaylarde 2014) .

Image 3: Growth of cyanobacteria in humid areas.    Source: https://www.iaph.es

IDENTIFICATION METHODS

Biodegradation is routinely measured by applying chemical and physiological assays to laboratory incubations of flasks containing pure cultures of microorganisms, micex cultures, or environmental samples (e.g., soil, water, sediment, or industrial sludges. Figure X provides a conceptual overview of major determinants of biodergadability. (Madesn, Eugen, I. 2002)

Image 4: Conceptual overview of major determinants of biodegradability. The mechanisms by which microorganisms catalyse biodegradation reactions are defined by interactions between the context-dependent thermodynamic stability of the substrate and the evolution. (Madse, Eugen, I. 2002)

The microbiological analysis of cultural heritage consists of identifying the microorganisms (bacteria, fungi, algae) responsible for the damage caused to the materials that constitute the work under study. This requires the taking of samples (using sterile material) and subsequent culture in the laboratory. The developed colonies are studied by observation through optical and electronic microscopy and / or molecular biology techniques.

Recently, these traditional microbiology methods based on isolation techniques and laboratory culture are being complemented by molecular biology techniques, based on the detection of DNA and subsequent analysis of the obtained DNA sequences.

The development and use of (molecular) techniques of rapid identification of microorganisms without the need for cultivation and isolation is important, and in this way we know which biofilm communities that are on the surface, since only in the laboratory It is possible to identify those microorganisms that can be cultivated and isolated and which only make up 1% of the entire community (Crispim, C. A., Gaylarde C. C. 2005).

There was a study that talks about microorganisms that cause biodeterioration by molecular biology techniques in the IAPH. The molecular techniques used in the IAPH are based on the specific amplification of certain sequences of deoxyribonucleic acid (DNA) from the complete genome of a microorganism. These sequences have been selected because they are unique and characteristic of each species, which allows them to be used to differentiate different species within a complex microbial community, such as the case of a microbial colonization in a specific cultural asset (monuments, works of historical interest -artistic, etc.).

The molecular method of detection and identification of microorganisms includes several steps: extraction of DNA; amplification by the polymerase chain reaction (PCR) of a target sequence; sequencing (determination of the base sequence) of the amplified DNA; in silico analysis of the sequence. (Chaparro, Menguiano, Víctor M, et al 2013)

METHODOLOGY TO PREVENT OR ERRADICATE IT

The methods used to prevent biodeterioration must consider the inhibition of the growth or metabolic activity of the organisms and the modification of the characteristics of the environment where the deterioration process takes place (Giudice, 2003).

The most used method is Cleaning:

It is essential to carry out a preliminary inspection, in order to determine the type of material (marble, stone, bronze, etc.) and the degree of deterioration (type of dirt, surface roughness, etc.).

The selection of the cleaning method depends on the nature and condition of the substrate, also on the type of microorganisms.

The cleaning can be:

Mechanics: includes any method capable of removing the material deposited on the surface. Includes brushing, cleaning spheres etc. and it is applied to remove incrustations, patinas and the bacteria associated with different materials. This cleanses must be accompanied by water and a biocidal agent to remove from the surfaces the organisms responsible for biodeterioration.

Chemistry: generally applied after mechanical cleaning. The products used include mineral acids, organic and oxidizing and non-oxidizing and natural biocides. Also can use cleaning techniques with steam, hot water and detergents; Flame or flamed action; use of solvents; blasting with abrasive materials; laser, etc.

Currently, to prevent the formation of mold and biofilms, there are specialized paints and varnishes.

CONCLUSIONS

Biodegradation by microorganisms is a process that can affect all types of materials (for example, wood, paper, rocks, concrete, metals, paintings, plastics and other polymers). And they carry out many different types of organisms (Cyanobacteria and green algae, sulfur bacteria, nitrifying bacteria and Halophilic bacteria). These microorganisms degrade the materials to form the energy needed to live. Depending on the metabolism of individuals, they will degrade a type of material or another.

REFERENCES

Ascaso, C., Wierzchos J., Souza-Egipsy V., De los Ríos A., Delgado J. 2002. Int. Biodet. Biodegr. 49:1-12.

https://www.researchgate.net/publication/294694688_In_situ_microscopy_diagnosis_of_biodeterioration_processes_in_monument_rock

Biodeterioro del patrimonio cultural.(7/12/1018).Retrieved from: https://www.iaph.es/web/canales/Ciencias_Experimentales_y_Patrimonio_Cultural/biologia/biodeterioro/microbiologia.html

Chaparro Menguiano Víctor M. i Castiñera Pérez Román J. i Puerto Sameño M. (2013) Estudio de microorganismos causantes de biodeterioro mediante técnicas de biología molecular en el IAPH. Ph84 proyectos y actuaciones. (84), 174-187. Retrieved from:  http://www.iaph.es/revistaph/index.php/revistaph/article/download/3379/3374

Crispim, C. A., Gaylarde C. C. 2005. Microbial Ecol. 49(9):1-9. https://www.researchgate.net/publication/7856965_Cyanobacteria_and_Biodeterioration_of_Cultural_Heritage_A_Review

Dra.Sandra Gómez de Saravia (2006), Biodeterioro del patrimonio cultural. Preservación y conservación (7/12/2018). Retrieved from: https://digital.cic.gba.gob.ar/bitstream/handle/11746/1064/11746_1064.pdf?sequence=1&isAllowed=y

Gaylarde, C. (2014). Biodeterioration of historic buildings in Latin America. Conference: 9th Intl. Conf. Durability of Building Materials and Components, At Brisbane, Australia, (November), 1–9. Retrieved from: https://www.irbnet.de/daten/iconda/CIB9274.pdf

López, P. 2012. Clarificando las diferencias entre biodegradación, biosaneamiento, biocatálisi y biodeterioración. Rev. LatinAm. Metal.Mat.

http://www.rlmm.org/ojs/index.php/rlmm/article/view/390

Madsen Eugen L.(2002) Manual of environmental microbiology (2na edició). Amer Society for Microbiology

Sterflinger, K., Piñar, G. (2013) Microbial deterioration of cultural heritage and works of art. Retrieved from:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3825568/

Videla, H. A., Guiamaet P. S., Gómez de Saravia S. G. 2003. Rev. Museo La Plata. 44:1-11.

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