Cyanobacteria attack rocks: control and preventive strategies to avoid damage caused by cyanobateria and associated microorganism in roman hypogean monuments
CATS
EVK4-CT2000-00028
| :: Work description | ||
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Roman hypogea, and the works of art that they contain, need to be protected against the biodeteriorative action of microorganisms developing on rock surfaces. The wide distribution of these archaeological remains in Southern Europe, and their cultural, artistic and religious importance, emphasises the potential social impact that biological damage can wreak on these monuments. Furthermore, the similarity of their habitat to that of other natural and man-made hypogea (show caves, subterranean churches and historical buildings), make them one of the best candidates in which to develop and apply innovative approaches to sustainable management. In these environments the abundance of nutrients in the lithic substrata, the input of compounds from circulating air and percolating waters, and the high humidity combined with the presence of artificial illumination, provide a suitable niche for those photosynthetic microorganisms that can make use of the spectral emission of lamps. The continual influx of visitors can, in itself, cause significant climatic changes, by providing a source of heat and of CO2. Cyanobacteria, thanks to their peculiar ability to adapt to extremely low photon flux densities and to acclimate to a variety of spectral emissions, are the major organisms responsible for biofilm formation on any rock surface (i.e. mortar, bricks, marble, frescoes, stuccoes, mosaics, etc.) exposed to light. At the same time, the availability of organic matter produced via cyanobacterial photosynthesis supports the growth of associated heterotrophic microorganisms (bacteria and fungi), the development of which contributes in a synergic manner to the establishment of the biofilm and to the increase of the biological activity on the colonised surface.
The problem of conservation, restoration and exploitation of Roman hypogea is part of the more general need to safeguard of the Cultural Heritage of Europe. This heritage has a significant influence on the economy of nations rich in archaeological remains, including most of the Mediterranean countries, and influences two main socio-economic factors: the significant amount of human and financial resources needed to preserve important archaeological sites and the improvement of both tourism and the quality of life through a sustainable management of the artistic patrimony of Europe. |
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| :: Scientific objectives and approach | ||
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The proposal CATS focuses on the control, prevention and monitoring of cyanobacteria-dominated biofilms that cause damage to rock surfaces in Roman hypogea. It develops and integrates physical and biotechnological methods intended to limit the growth of microorganisms on valuable archaeological surfaces, and applies analytical methods to monitor the presence and the extent of the microbial damage. The common effort of the multidisciplinary and integrative group of scientists, conservation managers and SMEs brings together expertise in areas such as petrology, geology, chemistry, biochemistry, microbiology, phycology, archaeology, art restoration and conservation, diagnostics and environmental technology. It has been described for other environments that the metabolic activity of cyanobacterial biofilms leads to the biotransformation and biodecay of substrata. In Roman hypogea, the mechanisms that cause severe damage mostly to calcareous substrata, and that are consequent to the development of phototrophic and heterotrophic microorganisms, still have to be understood. Accordingly, CATS will answer the following two major and essential questions in order subsequently to develop control and preventive strategies:
- How does microbial activity alter the mineralogical, textural and geochemical features of rocks? - What conditions limiting growth of cyanobacteria can be safety applied in Roman hypogea? To achieve these central objectives different types of microsensors will be developed. These will be used to quantify biologically induced variation of gases and ions on the colonised lithic substrata. Data on the petrological and geochemical characteristics of rocks and on structure, function and diversity of biofilms will be integrated with those obtained using microsensors in order to describe and model the damage of rock surfaces. This part of the project will end with the construction of a multiparametric portable device based on microsensors that will be produced as a new tool for microbial monitoring. In the other part of the project, a pilot study will be set up to investigate the possibility of using a new lighting system providing wavelengths poorly used by cyanobacterial photosynthesis. This will drastically decrease the growth of cyanobacteria and therefore the quantity of organic matter available to the associated heterotrophic populations. Subsequently, the new lighting system will be experimentally set up in situ in order to confirm the laboratory results. At the end of this part, the public response to the innovative strategies proposed will be tested and the benefit to cost ratio of a new illumination system in Roman hypogea will be evaluated. In addition to the physical approach, newly identified biomolecules related to iron metabolism and cell-to-cell signalling pathways will be checked for their ability to interfere with bacterial and, especially, cyanobacterial metabolism by removing factors indispensable to microbial development. The application of these environmental biotechnologies under laboratory conditions should provide a new method to control and prevent growth of phototrophic biofilms. |
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| :: Scientific/Technical objectives and innovation | ||
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Specific objectives of the project are:
· to characterise the geological, geo- and hydrochemical, and physical environment of rocks unaffected or colonised by cyanobacterial communities inside Roman hypogea, and to evaluate possible preferences of cyanobacteria and associated microorganisms for specific lithologies; · to describe the architecture and functioning of biofilms built by cyanobacteria and associated microorganisms on different types of lithic surfaces;to ascertain the most critical physical, chemical and biological factors that control colonisation of rock surfaces; · to assess and quantify the damage caused by cyanobacterial biofilms to different types of surface;to develop new physical methods to control and prevent biofilm growth using wavelengths in the visible part of the light spectrum that are, at best, poorly used by photosynthesis; · to identify siderophores and cell-to-cell signalling biomolecules and experimentally to test their potential to interfere with biofilm development;to develop an innovative monitoring method using a multiparametric microsensor device for the measurement of biogeochemical parameters on endangered rock surfaces; · to test the response and expectation of citizens to the innovative strategies proposed. |