P. S. Guiamet

Biodeterioration of Mayan archaeological sites in the Yucatan Peninsula, Mexico

Many of the monuments of the Mayan civilization are suffering deterioration caused by environmental factors (high temperatures and relative humidities), increasing contamination from natural and anthropogenic sources, and by the action of micro- and macro-biological communities. Archaeological sites and historical monuments in the Mayan area were constructed with different limestones which offer different resistances to degradation by the various types of contamination. Two different sampling sites were chosen at the archaeological site of Uxmal in the Yucatan Peninsula, Mexico. Heterotrophic bacteria, cyanobacteria and different fungi were isolated and classified taxonomically. The other archaeological site chosen for this study was the fortress of Tulum, located at the side of the Caribbean Sea and exposed to chloride of marine spray and sand erosion. In this case, heterotrophic aerobic and anaerobic bacteria, cyanobacteria and fungi were isolated from the four sampling areas selected. In both archaeological sites crust deposits were observed by using light microscopy, SEM and ESEM. Surface analyses were made by means of EDAX and electron microprobe. Possible mechanisms of stone decay, based on the type of microorganisms isolated, the physico-chemical characteristics of the constructional materials and environmental factors are discussed.

Biodeterioration of Mayan buildings at uxmal and tulum, Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.

Biodeterioration of funeral sculptures in La Recoleta Cemetery, Buenos Aires, Argentina: Pre- and post-intervention studies

Stone materials exposed to weathering are subject to biological colonization and consequently to biofilm formation, causing biodeterioration. The color changes on the stone substrates caused by biogenic pigments, mechanical stress on the mineral structure due to extracellular polymeric substances (EPS) and the accumulation of atmospheric pollutants by the biofilm are some of the deteriogenic effects, which modify esthetic and functional aspects of the work. The aim of this study was to determine biodeterioration and biofilm formation on marble tombstones from La Recoleta Cemetery, Buenos Aires, Argentina. The effect of the biocide benzalkonium chloride on biofilm formation was studied, and a chart produced of the treated tombstones. Pre- and post-intervention microbiological studies, scanning electron microscopy and X-ray dispersion analysis showed a significant decrease of the biofilm flora after treatment. However, algae of the genus Trentepohlia were difficult to eradicate. These studies are a valuable contribution to determine restoration criteria against biofilm formation, to characterize chromatic variations of biological origin on the stone and to formulate conservation and restoration policies.

An environmental assessment of biodeterioration in document repositories

Experiments were designed (1) to investigate the bioadhesion, biofilm formation, foxing, and micropitting in documentary collections, (2) to assess the risk of biodeterioration, (3) to investigate the environmental microbial concentration, and (4) to study the influence of environmental factors in biodeterioration of documentary heritage in three archives. The importance of this work in the field of biodeterioration of documentary heritage was verified by bioadhesion and biofilm formation by microorganisms isolated from the collections under study. Bacillus sp. and Scopulariopsis sp. isolated from paper books showed considerable evidence of attacking the paper structure and of pigment production, constituting a hazard to the loss of documentary heritage.

Scopulariopsis sp. and Fusarium sp. in the Documentary Heritage: Evaluation of Their Biodeterioration Ability and Antifungal Effect of Two Essential Oils

Fungi produce pigments and acids, generating particular local conditions which modify the physicochemical properties of materials. The aims of this work are (i) to investigate bioadhesion, foxing production and biofilm formation by Scopulariopsis sp. and Fusarium sp. isolated from document collections under laboratory conditions; (ii) to verify attack on cellulose fibres and (iii) to study the possibility of reducing fungal growth using natural products. Biofilm formation and extracellular polymeric substance (EPS) production by fungi were demonstrated in laboratory assays and by scanning electron microscopy (SEM) observations. The biocidal activity of two essential oils of Origanum vulgare L. and Thymus vulgaris L. was evaluated using the microatmosphere method. SEM observations showed that these strains were able to attach to paper and form biofilms, causing damage on them, which demonstrates the biodeterioration ability of these microorganisms. Scopulariopsis sp. and Fusarium sp. isolated from paper books showed the formation of fox-like reddish-brown colour spots, attack to the paper structure and pigment production on aged paper samples. The strains tested produced a decrease in the pH of one unit. This would substantiate the effect of the strains in paper biodeterioration. The microatmosphere method showed that volatile compounds of the essential oils have antifungal activity.

Biofilm Effects and MIC of Carbon Steel in Electrolytic Media Contaminated with Microbial Strains Isolated from Cutting-Oil Emulsions

Abstract SAE 1020 carbon steel samples were tested in laboratory experiments using two different microbial strains isolated from cutting-oil emulsions: Pseudomonas fluorescens and Desulfovibrio vul...

Fungi and bacteria in the biodeterioration of archeological fibers. Analysis using different microscopic techniques.

Fil: Guiamet, Patricia Sandra. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico la Plata. Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina