Evaluating the microbiological risk to a contemporary Nigerian painting: Molecular and biodegradative studies

• Microscopy and molecular techniques were used to study biodeterioration of a canvas painting.
• Epifluorescency showed that the colonizing microorganisms were in an active state.
• Bacillus and Ascotricha were the dominant species.
• Cellulolytic potential of isolated organisms indicates their biodeteriorative role on the artwork.

The microbiological risk to a contemporary oil painting on canvas from Nigeria showing stains putatively caused by microorganisms was assessed with non-invasive (nitrocellulose membrane and fungi tape) and microinvasive (fibres) sampling techniques as well as culture-dependent/-independent methods. Optical microscopy observation of fungi-tape showed that there were more surface-associated microorganisms on the discoloured areas of the canvas painting compared to non-discoloured areas. Epifluorescency data demonstrated that the colonizing microorganisms were in an active metabolic state. A higher microbial count obtained from the discoloured fibres implied that the deterioration may be of microbial origin. Bacterial strains isolated were phylogenetically related to members of the phylum Firmicutes and Proteobacteria while the fungi belonged mainly to the phylum Ascomycota. The dominant genera were Bacillus and Ascotricha, respectively for bacteria and fungi. Cellulolytic assay performed to ascertain the potential of the isolates to degrade cellulose, the major component of canvas, revealed that all the fungal and seven of the bacterial strains could attack cellulose, thereby making them potential biodeteriogens of the artwork. To the best of our knowledge, this is the first report from Sub-Saharan Africa demonstrating the application of molecular techniques to the study of microbial deterioration of a cultural heritage object.