Colored stains: microbial survey of cellulose-based and lignin rich paper

Paper is one of the oldest media used by humanity to write and pass on its knowledge and thoughts. During the centuries diverse types of paper were produced and were characterized by a different ratio of natural macromolecules, mainly lignin and cellulose. Handmade paper has a higher content of cellulose respect to the early machine-made paper, where the lignin is the other important component. Microorganisms are able to colonize and deteriorate both types of papers. In addition, they can release on their surfaces pigments and colorants which produced anaesthetic stains. We analysed the microbiota in library and archive environments together with that colonizing 17 stains present on handmade and machine-made paper surfaces. The investigation strategy included the combination of microbiological and high-throughput sequencing (HTS) approaches. The culture-dependent methodology comprised: isolation, DNA identification, hydrolytic and paper staining assays. The HTS was performed by MinION platform and for the mycobiome a more suitable bioinformatics analysis pipeline, MetONTIIME based on QIIME2 framework, was applied. The paper model staining assay permitted us to directly recognize the colorizing isolates which in combination with sequencing data evidenced a complex microbial community which have the potentiality to stain the two types of paper. Staining abilities (diverse shades of grey, pink and beige) were confirmed by frequently isolated and detected fungi (Alternaria, Cladosporium, Aspergillus, Penicillium, Pithomyces chartarum, Fusarium, Epicoccum and Mucor fragilis) and also new ones such as Roussoella euonymi and Achaetomium. We have also evidenced the staining ability, different shades of pink and beige, of bacteria: Pedobacter, Pseudomonas and Paracoccus. Moreover, pigments producing bacteria, such as Bacillus, Propionibacterium, Ralstonia, Bradyrhizobium and Sediminibacterium were also detected