Escudero-Leyva, E. | Search bioRxiv

bioRxiv2024

Reduced functional fungal communities in two species of sloths (Bradypus variegatus and Choloepus hoffmanni) suggest a link to slow digestion

Sloths, with their ruminant-like digestive systems, possess the slowest digestion among mammals due to their low metabolic rate, minimal food intake, and extremely low-energy diet. However, no comprehensive studies have characterized the sloths gut microbiota, including fungi, and their role in digestion. This study hypothesized that effective plant fiber-degrading fungi (e.g., Neocallimastigomycota) would be scarce in the sloths gut. The aim was to describe the gut microbiota of three-toed (Bradypus variegatus) and two-toed (Choloepus hoffmanni) sloths to understand their link to slow digestion. Microbial composition and functionality were analyzed using shotgun metagenomics, metatranscriptomics, fungal metabarcoding (ITS 1 and 2 nrDNA), and cellulose degradation analysis. Microbial communities were dominated by bacteria (92-97%), followed by viruses (1-7%). Fungi accounted for only 0.06-0.5% of metagenomic reads and 0.1% of transcripts. Functional analysis revealed minimal CAZy abundance (1.7-1.9% in metagenomes, 0.2% in metatranscriptomes), with no fungal CAZys or glycoside hydrolases detected. Neocallimastigomycota had negligible abundance in metagenomic data and was absent in metatranscriptomic or ITS metabarcoding data. Bradypus variegatus showed overall lower CAZy abundance and fungal presence compared to Choloepus hoffmanni. Lastly, cellulose degradation analyses revealed that only [~]5-35% of the intake was digested. This study highlights the unique microbial ecosystem in sloths guts, showing minimal presence of plant fiber-degrading anaerobic fungi and limited microbial CAZys, aligning with their slow digestion and low metabolic rate, thus enhancing our understanding of their digestive efficiency and metabolic adaptations.

microbiology↗

bioRxiv2022

Fungi with history: Unveiling the mycobiota of historic documents of Costa Rica

Through nondestructive techniques, we studied the physicochemical characteristics and mycobiota of five key historic documents from Costa Rica, including the Independence Act of Costa Rica from 1821. We determined that for documents dated between 1500 and 1900 (i.e., the Cloudy Days Act, the Independence Act, and two documents from the Guatemalan Series from 1539 and 1549), the paper composition was cotton, whereas the 1991 replicate of the Political Constitution from 1949 was made of wood cellulose with an increased lignin content. We also determined that the ink employed in 1821 documents is ferrogallic, i.e., formed by iron sulfate salts in combination with gallic and tannic acids. In total, 22 fungal isolates were obtained: 15 from the wood-cellulose-based Political Constitution and seven from the other three cotton-based documents. These results suggest that cotton-based paper is the most resistant to microbial colonization. Molecular identifications using three DNA markers (i.e., ITS nrDNA, beta-tubulin, and translation elongation factor 1-alpha) classified the isolates in eight orders and ten genera. The most frequent genera were Cladosporium, Penicillium, and Purpureocillium. Of the isolates, 95% presented cellulolytic activity correlated to their ability to cause deterioration of the paper. This work increases the knowledge of the fungal diversity that inhabits historic documents and its relationship with paper composition and provides valuable information to develop strategies to conserve and restore these invaluable documents.

microbiology↗