RICHNESS, CELLULOLYTIC ACTIVITY, AND FUNGICIDE SUSCEPTIBILITY OF FUNGI FROM A BIRD BIOLOGICAL COLLECTION

Riqueza, actividad celulolítica y susceptibilidad a fungicidas de hongos de una colección biológica de aves

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Citation / Citar este artículo como: Arenas-Castro H, Muñoz-Gomez SA, Uribe-Acosta M, Castaño-Castaño L, Lizarazo-Medina PX. Richness, cellulolytic activity,and fungicide susceptibility of fungi from a bird biological collection. Acta biol. Colomb. 2016;21(1):167-173. doi: http://dx.doi.org/10.15446/abc.v21n1.49240

Biological collections store the past and present of worldwide biodiversity. They are unique examples of the evolutionary lineages extracted from the natural environment. Every specimen represents the long-term efforts of researchers as well as an investment of public funds. Their value as a whole increases when it is realized that contrary to art collections, where a unique piece is the focus, biological collections encompass many specimens of the same kind in order to reflect the natural variation present within populations and species (Simmons and Muñoz, 2005; Lewis, 2008). These collections play important roles in educational purposes and biodiversity research (Lee and Balick, 2007; Delgadillo and Góngora, 2009). They can guide us in studying evolution, biological invasions, environmental and climate change, pathogens, vectors of disease, and conservation decision-making (Ponder et al., 2001). Many publications in ecology and evolutionary biology provide evidence for this, as they heavily rely on work previously done on biological collections. Therefore, conserving biological collections saves both institutions and taxpayers hundreds of millions of dollars per year (Páez, 2004; Suárez and Tsutsui, 2004).

Currently, budgetary shortfalls are not the sole threat to biological collections. Biodeterioration caused by bacteria, fungi, arthropods, and rodents threats cultural and natural heritage worldwide (Simmons and Muñoz, 2005; Sterflinger, 2010). Fungi are especially problematic because they can degrade a wide array of biological compounds. Their preferences for keratin- and cellulose-based material, in addition to their great dispersal capability via spores and resistance to adverse environmental conditions, make them a pest hard to deal with (Saddler, 1985; Błyskal, 2009). Fungi cannot only corrode, color and digest organic materials, they can also cause allergies and respiratory problems in museum staff (Merritt, 2007). Their control demands active removal and reduction of growth rate and spore load in storerooms. Diverse chemical agents are commonly used to achieve this, but non-toxic alternatives are constantly pursued to avoid damage to biological specimens as much as possible (Knell, 1994).

Bird beaks, claws, scales, and feathers are characterized by the presence of keratin proteins (Frenkel and Gillespie, 1976; Sawyer et al., 2000). Wood supports, which bird specimens generally lay on, are a rich source of cellulose. Thus, museum material derived from animals is particularly vulnerable to biological attack due to its high carbohydrate and protein composition (Keopannha, 2008). Some surveys in biological collections and poultry birds have identified Aspergillus, Penicillium, Cladosporium, Trichophyton, Chrysosporium , and Rhizopus as the most common fungi genera present in their surfaces (Gründer et al., 2005; Shabbir et al., 2007). Among them, Penicillium, Aspergillus , and Rhizopus contain species with reported cellulolytic activity (Jahangeer et al., 2005; Devi and Kumar, 2012; Khokhar et al., 2012; Damaso, 2012).

We aimed at identifying the taxonomic affiliation of fungi isolated from bird specimens from the biological collection at Museo Universitario de la Universidad de Antioquia (MUUA). This collection represents 60 years of avifauna samples from Colombia, the country with the highest avian diversity in the world (Donegan et al., 2014). Having first diagnosed the fungi responsible for biodeterioration, we then evaluated their susceptibility to two previously reported low-toxicity chemical agents. We also evaluated the cellulolytic activity of these fungi. Interpretation of the results allowed us to propose actions to control the bird collection fungi-pests.

Reports of fungi affecting birds are common, but according to our review, no survey has been conducted on bird collections.

We identified some genera, such as Aspergillus, Chaetomium, Chrysosporium, Cladosporium, Curvularia, Penicillium, Trichoderma, and Thichophyton , that have been previously isolated from free-living and poultry bird feathers (Pugh, 1972; Kaul and Sumbali, 1999; Deshmukh, 2004; Gründer et al., 2005). Those genera represent 91 % of isolated morphotypes. Most of them have also been associated with air contamination of museum’s indoor environments (Arya et al., 2001; Shabbir et al., 2007; da Costa et al., 2011). This suggests that the fungi affecting the MUUA bird collection could come from both airborne spores and specimens themselves.

A sample of 11 fungi, representing 77 % of isolated genus diversity, exhibited cellulolytic activity. Nearly half of them exceeded or matched the cellulolytic activity of a control cellulolytic strain. These results suggest that the persistence of the MUUA bird collection’s fungal contamination is mainly being driven by fungi that are able to degrade cellulose. Those environmental fungi found a rich cellulose substrate in the wood supports on which most of the avian specimens lay and from which more than a half of the injuries come from. The capability to degrade cellulose is not restricted to fungi, as some bacteria and insects produce cellulases too (Watanabe and Tokuda, 2001). However, fungi are especially ubiquitous due to the ability of their spores to facilitate the permanent colonization of new substrates. This scenario is favored by specimens being stored in close proximity to each other within interconnected cabinets. Although not tested here, keratin preference of some isolated fungi can also be responsible at some extent for fungal contamination and persistence. Indeed, some genera reported here, such as Aspergillus, Chaetomium, Cladosporium, Chrysosporium, Curvularia, Penicillium, Pestalotia, Syncephalastrum, Trichoderma , and Trichophyton , contain keratinolytic species (Błyskal, 2009). Keratin rich bird body parts like claws, beaks, feathers, and scales are ideal substrates for keratinolytic fungi (Korniłłowicz-Kowalska and Bohacz, 2011).

Regardless of whether the cellulolytic or keratinolytic activity favor fungal contamination, an integrated pest management control program should focus on air quality monitoring in order to identify the optimal temperature, relative humidity, and other relevant environmental variables that might lead to a reduction in air-spore load (Abe and Murata, 2014). A temperature below 20 °C and humidity below 65 % is recommended to prevent the growth of fungi (Simmons and Muñoz, 2005). This necessity is strengthened when it is considered that all fungal spores may be allergenic, especially those belonging to Aspergillus and Penicillium genera, which sum up 60.5 % of identified fungi (Kurup et al., 2002). If actions are not taken, an increase in biodeterioration of biological collections can be a hazard to the health of museum staff and visitors. This biological contamination in buildings can trigger temporal mucosal, skin, and general problems in workers, as is predicted by the sick building syndrome (Li and Yang, 2004).

A pest-control program should contemplate appropriate storage facilities for preventing contamination, as well as constant surveillance of specimens for accidental moldlike growth (Knell, 1994). Furthermore, lesions caused by occasional contaminations can be treated with fungicides that kill or retard fungal growth. In this study, we have shown the effectiveness of two low-toxicity chemical agents that significantly slow down the growth rate of fungal genera isolated from bird specimens. Incipient lesions can be controlled by spraying 10 mM ZnCl, which acts by interacting with sulfhydryl groups of proteins and altering their functions in the fungus (Xu and Imlay, 2012). Alternatively, salicylic acid disrupts ion transport within fungal cells (Amborabé et al., 2002). They have been effective controlling other fungi genera applied in solid and liquid media (Amborabé et al., 2002; Malachová et al., 2011). These two different fungicides emerge as promising candidates that can be implemented in bird biological collections, thus reducing risks to the health of the museum’s staff. Although ZnCl was more effective that salicylic acid, the latter is nearly 40 % cheaper, being a cost-effective alternative.

Our study is the first survey done on a bird biological collection aimed to both identify fungi causing deterioration and characterize the properties that could be responsible for their colonization and persistence. We identified at least 25 fungi species, most of which were able to degrade cellulose. Target low-toxicity chemical fungicides reduced fungal growth rate to different extents. Further research should address the ecological aspects of the contamination, such as the provenance of fungi (environmentally acquired post-fixation or bird-indigenous pre-fixation), the relative contribution of fungi’s ability to degrade cellulose, lignin, and keratin to the persistence of contamination, and the possible interactions among the surface microbiota on preserved bird specimens. The present study has opened up interesting new lines of research that will eventually contribute to the understanding of contamination dynamics in biological collections. It also offers a practical solution by proposing a set of strategies that can be implemented in a cost-effective manner in a small, local, and budget-limited university museum.

Associate Editor: Enrique Arbeláez-Cortés.

We thank to Ana Isabel Gutiérrez Gallo for her collaboration and technical support, to Isabel Carmona, Isabel Mesa, Marcelina Mendoza, and Diana L. Gómez for their laboratory assistance, and Alexis Acosta and Fernando Valencia for their assistance in sampling at the MUUA. We are grateful to Maicol Ospina-Bedoya for his crucial role in the initial conception of the research project and Tawni Voyles for her comments on the manuscript. We appreciate the efforts made by the MUUA to preserve its biological collections. We also thank to Corporación Académica para el Estudio de Patologías Tropicales (CAEPT). This project was funded by the program Incentivos a la Investigación of the Vicerrectoría de Extensión of the Universidad de Antioquia. Two anonymous reviewers made valuable comments that improved this work.