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Characterisation of the microbial communities in the gastrointestinal tract of wood-eating organisms

Student thesis: Doctoral Thesis

  • Caroline Louise Marden
Wood recycling is key to biogeochemical cycling and largely driven by microorganisms, with bacteria and fungi naturally coexisting together in the environment. Terrestrial isopods Oniscusasellus and Porcellio scaber have adaptations to enable them to colonise diverse terrestrial environments and scavenge on dead and decaying organic matter that is rich in cellulose. The Amazonian catfish, Panaque nigrolineatus have physiological adaptions enabling the scraping and consumption of wood, facilitating a detritivorous dietary strategy. Substrates high in lignocelluloseare difficult to degrade and as yet, it is unclear whether these organisms obtain any direct nutritional benefits from ingestion and degradation of lignocellulose. However, there are numeroussystems that rely on microbial symbioses to provide energy and other nutritional benefits for host organisms via lignocellulose decomposition. Whilst previous studies on the microbial communities of O. asellus, P. scaber and P. nigrolineatus, have focused upon the bacterial populations, the presence and role of fungi in lignocellulose degradation has not yet been examined. These studies describe the bacterial and fungal communities within the gastrointestinal tracts using next generation sequencing. The hepatopancreas of O. asellus and P. scaber was predominantly colonised by one bacterial species and had more fungal diversity. The hindgut was colonised bymore diverse bacterial and fungal communities. Due to the woodlouse inhabiting diverse environments, including those with heavy metal pollution, culture methods were used to detect antimicrobial resistance in the gastrointestinal tract of woodlice. The effects of diet on enteric fungal populations were examined in each gastrointestinal tract region of P. nigrolineatus and fungal species were found to vary in different regions of the gastrointestinal tract as a function of diet. This is the first study to investigate the bacterial and fungal communities within the hepatopancreas and hindgut from two species of woodlice, using the same individual woodlouse,using next generation sequencing. This is the first study to detect fungi in the digestive tract of anywoodlice. 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. This study provides new insights into the microbial communities that may have a symbiotic role involved in wood degradation in the GI tracts of woodeating organisms. This study also highlights the need for further research into fungi inhabiting many diverse environments to give more complete and balanced information about the absence and presence of microorganisms.
Original languageEnglish
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Award dateMar 2019

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