MICROBIOLOGICAL IMAGE

http://dx.doi.org/10.1016/j.ram.2016.10.004

Fungi observation in deteriorated wooden heritage: analysis using different imaging techniques

Observación de hongos xilófagos en madera perteneciente al patrimonio histórico deteriorada: análisis utilizando diferentes técnicas de obtención de imágenes

 

Paula V. Alfieri^*, María V. Correa

Laboratorio de Entrenamiento Multidisciplinario para la Investigación en Tecnología (L.E.M.I.T), Heritage Restoration and Conservation Area, Microbial Culture Laboratory, La Plata, Buenos Aires, Argentina

Received 2 May 2016; accepted 5 October 2016
Available online 12 March 2017

* Corresponding author.
E-mail address: paulaalfieri@gmail.com (P.V. Alfieri).

0325-7541/© 2016 Asociación Argentina de Microbiología. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

 

This study was based on the current deteriorated status of wood slats from a locomotive turntable at the La Plata Provincial Railway Station⁶ (Fig. 1). Wood species of the slats was Schinopsis spp. and was determined by conventional methods, while the fungal species was Phellinus chaquensis (white-rot fungus) and was determined morphologically. Determination of the fungus and its in vitro cultural features was based on Iaconis and Wright¹ and Robledo and Urcelay⁴.

Figure 1 Actual photographs of La Plata Provincial Railway Station. Panel A: Front view of the central station building. Panel B: Back view of the central station building. Panel C: Aerial view of the location of the locomotive turntable (34°56′16″ S and 57°56′13″ W) and Panel D: locomotive turntable status.

Fungal degradation requires to be measured by non-destructive methods²: the area occupied by mycelium and basidiomata was observed by using X-rays and computed tomography (CT) and was quantified by image analysis using ImageJ software. Grayscales of the images obtained indicated density changes, being the black scale the less dense and the white scale the densest. To establish microstructural wood deterioration (cell wall), scanning electron and optical microscopy (SEM and OM) images were analyzed.

The radiographic images were analyzed using ImageJ to determine the affected area by wood decay fungi: the mycelium area was 84.6%, while the basidioma occupied 12% of the total wood area, which confirms that the external deterioration did not correlate with the internal status. To substantiate this fact, a CT scan was performed. CT images showed the wood structure loss (dark plates in the images, Fig. 2), which was correlated with the presence of fungal hyphae along the entire slat.

Figure 2 Locomotive turntable wood status. Panel A: X-ray images (RX) of the deteriorated wood. Panel A: RX image of deteriorated wood where the dark parts of the image represents a loss of wood material correlating with the presence of fungal hyphae. Panel B and E: Computed tomography (CT) scan of deteriorated wood to analyze internal wood status; dark areas of the image are less dense due to the loss of material and the dark area of the image coincides with the presence of fungal mycelium. Panel C: Photograph of slats in an advanced status of deterioration caused by environmental and biological factors subjected to RX and CT. Panel D: Detail of basidioma.

Finally, the wood microstructure was analyzed by SEM and OM images (Fig. 3), in which the advanced deterioration status of the wood structure could be observed, evidencing a high rate of fungal colonization (hyphae, panels A and B) and wood microstructure loss (cell wall degradation, panels C and D).

Figure 3 Microscopy of deteriorated wood samples. Panel A: scanning electron microscopy (SEM) images of ultra slim cut of dark area observed in RX and CT, dense presence of hyphae. Panel B: SEM image of ultra slim cut of gray zone where microstructure loss and the presence of spores are observed. Panel C: Optical microscopy (OM) images of the dark area observed in RX and CT: altered wood appeared compartmentalized by dark secretions deposited in axial/radial parenchyma and in vessel and cell lumina. Panel D: OM images where generalized cell wall erosion is evident (arrowheads holes in vessel elements and erosion of wood cell walls are observed.

It was concluded that using images for assessing wood deterioration is a non-destructive alternative methodology, which allows to measure the structural condition of the material. This is essential in heritage conservation because it allows to correctly define the deteriorated status, which is useful for planning a conservation strategy that would prevent the loss of heritage assets^3,5.

Ethical disclosures

Protection of human and animal subjects

The authors declare that no experiments were performed on humans or animals for this study.

Confidentiality of data

The authors declare that no patient data appear in this article.

Right to privacy and informed consent

The authors declare that no patient data appear in this article.

Acknowledgements

To CICPBA (Comisión de Investigaciones Científicas de la Provincia de Buenos Aires) Directory Resolution No. 343/13; CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) from Argentina for their sponsorship for this research.

References

1. Iaconis C, Wright J. Studies on Basidiomycetes II. Systematic and biology of three species of Fomes. Anal Soc Cien Arg. 1953;151:10-24.         [ Links ]

2. Lehmann E, Vontobel P, Deschler-Erb E, Soares M. Non-invasive studies of objects from cultural heritage. Nucl Instrum Method. 2005;542:68-75.         [ Links ]

3. Parisi M, Piazza M. Restoration and strengthening of timber structures: principles, criteria, and examples. Pract Period Struct Des Constr. 2007;12:177-85.         [ Links ]

4. Robledo G, Urcelay C. Wood fungi in native trees of the middle region of Argentina. Argentina: Editorial Universitaria, Universidad Nacional de Córdoba; 2009. p. 1-201.         [ Links ]

5. Sterflinger K. Fungi: their role in deterioration of cultural heritage. Fung Biol Rev. 2010;24:47-55.         [ Links ]

6. Tartarini J. Patrimonio ferroviario Bonaerense. Pasajeros Al tren. Dirección Provincial de Patrimonio Cultural; 2009. p. 1-220.         [ Links ]