Browsing by Subject "wood"
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Item Investigation into the fungal diversity within different regions of the gastrointestinal tract of Panaque nigrolineatus, a wood-eating fish(AIMS Press, 2017-09-04) Marden, Caroline L.; McDonald, Ryan; Schreier, Harold J.; Watts, Joy E.M.The Amazonian catfish, Panaque nigrolineatus have several physiological adaptions enabling the scraping and consumption of wood (xylivory), facilitating a detritivorous dietary strategy. Composed of lignocellulose, wood is a difficult substrate to degrade and as yet, it is unclear whether the fish obtains any direct nutritional benefits from wood ingestion and degradation. However, there are numerous systems that rely on microbial symbioses to provide energy and other nutritional benefits for host organisms via lignocellulose decomposition. While previous studies on the microbial community of P. nigrolineatus have focused upon the bacterial population, the role of fungi in lignocellulose degradation in the fish has not yet been examined. This study describes the detection of fungi within the fish gastrointestinal tract. Using next generation sequencing, the effects of diet on enteric fungal populations were examined in each gastrointestinal tract region. Fungal species were found to vary in different regions of the gastrointestinal tract as a function of diet. This study is the first to examine the fungal community in a xylivorous fish and results support the hypothesis that diet influences fungal distribution and diversity within the gastrointestinal tract of P. nigrolineatus.Item The enteric microbiome of a novel wood-digesting organism: diversity of lignocellulolytic and nitrogen fixing communities of the Amazonian catfish, Panaque nigrolineatus(2019-01-01) McDonald, Ryan Christopher; Schreier, Harold J; Biological Sciences; Biological SciencesThe Neotropical catfish Panaque nigrolineatus imbibes large quantities of wood as part of its diet. This is an unusual feeding strategy among vertebrates as it imposes many dietary challenges. The most notable of these is the lack of assimilable carbon and nitrogen compounds. To overcome these dietary limitations, wood-feeding organisms rely on the lignocellulytic and diazotrophic activities of their enteric microbiomes. Characterization of the microbiomes of P. nigrolineatus through culture-dependent and molecular methods identified bacterial and fungal communities that were taxonomically distinct from all other wood-feeding organisms. Analysis of GI tract communities generated from anaerobic microcrystalline cellulose enrichment cultures and DNA stable-isotope probing approaches by 16S rRNA gene analysis revealed phylotypes sharing high sequence similarity to known cellulolytic bacteria including Clostridium, Cellulomonas, Bacteroides, Eubacterium and Aeromonas spp. Similar characterizations of the nitrogen-fixing community through enrichment culturing and community nifH sequencing revealed phylotypes that are closely related to Clostridium sp., Alpha and Gammaproteobacteria, and sequences associated with GI tracts of lower termites. In addition to the observed bacterial diversity, P. nigrolineatus also possess a resident cellulolytic fungal community comprised of Sordariomycetes and Dothideomycetes. Despite this unusual assemblage of microorganisms, the functional capacity of these communities is consistent with those observed in other wood-feeders. Manipulating enteric communities through diet revealed a high degree of taxonomic diversity but high functional resiliency. The microbiomes of both wood-fed and mixed diet-fed fish had high capacity for hemicellulose hydrolysis as the predicted metagenomes contained several classes of hemicellulases and lignin-modifying enzymes. However, communities from both diets appeared to lack the necessary cellobiohydrolases for efficient cellulose hydrolysis, suggesting that cellobiose is not the primary source of dietary carbon for the fish. Meta-analysis exploring the microbiomes of diverse wood-feeding and non-feeding animals suggest that the P. nigrolineatus gut environment selects for an enteric community based on function, rather than relying on vertically transferred symbiotic relationships. This is an unusual method of community assembly in wood feeding-organisms but may provide an advantage to organisms, like P. nigrolineatus, that switch between dietary strategies to survive in highly variable environments.