Behavior of the aeromicrobiote in two repositories of the National Archive of the Republic of Cuba during seven years of study

Abstract

En depósitos de archivos, bibliotecas y museos donde se conservan obras de valor patrimonial, la presencia de elevadas concentraciones fúngicas en el aire con potencialidades para degradar los soportes orgánicos constituyen un riesgo elevado para la preservación de ese patrimonio. En países de clima tropical estos efectos dañinos pueden potenciarse por los valores altos de humedad relativa y temperatura existentes durante la mayor parte del año. Los objetivos de este trabajo fueron: evaluar el comportamiento de la concentración microbiana aérea en el interior de dos depósitos del Archivo Nacional de la República de Cuba (ARNAC) en 7 años así como determinar la densidad y frecuencia relativa de los géneros y especies fúngicas para conocer su impacto ecológico y ambiental. Los muestreos microbiológicos se realizaron en la Fototeca y la Mapoteca empleando medios de cultivo apropiados y un método de sedimentación. Se determinó cualitativamente la actividad celulolítica, amilolítica y proteolítica, así como la excreción de ácidos y pigmentos. En la Fototeca la concentración fúngica se mantuvo más alta que en la Mapoteca durante el estudio y los géneros fúngicos predominantes fueron Aspergillus, Penicillium y Cladosporium aunque en algunos años Curvularia, Alternaria y Fusarium se detectaron a densidades relativas considerables, fundamentalmente en Fototeca. Las especies fúngicas de mayor impacto ecológico en los depósitos correspondieron a los géneros Aspergillus y Cladosporium. La mayoría de las cepas aisladas degradaron celulosa, gelatina y almidón, todas excretaron ácidos y más del 50% produjeron pigmentos de colores diversos.High concentration of microorganisms on air in repositories of archives, libraries and museums can degrade organic material and entails a high risk to cultural heritage preservation. In tropical countries, these harmful effects may be maximized by high values of temperature and relative humidity prevailing during most of the year. The aims of this research were: to study the behavior of air microbial concentration in two repositories of the National Archives of the Republic of Cuba (NARC) in 7 years and to determine the density and relative frequency of fungal genera and species as well as their ecological and environmental impact. The microbiological samples were taken in photo and map libraries by using an appropriate culture media and a sedimentation method. Cellulolytic, proteolytic and amylolytic activities as well as acid and pigment excretion on fungal isolates were qualitatively determined. Fungal concentration inside the photo library was higher than in the map library. The predominant fungal genera on air in both repositories were Aspergillus, Penicillium and Cladosporium, although considerable relative densities of Curvularia, Alternaria and Fusarium were detected in some years, mainly in the photo library. Aspergillus and Cladosporium genera were the fungal species with the greatest ecological impact on the repositories. Most of the fungi degrade cellulose, gelatin and starch. All strains excrete acids and over 50% of them excrete pigments of various colors. In both repositories, Gram-positive bacteria prevailed and their relative densities were higher in those years when the temperature and the relative humidity were higher (photo library in 2004, map library in 2007 and 2010). Ecologically, Bacillus and Streptomyces genera prevailed in the photo library and were frequent in the map library. These bacterial genera greatly contributed to biodeterioration because they have cellulolytic activity and so can degrade papers when the relative humidity is maintained at or above 90% during 24 h.Comité de Medio Ambient