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Zeibich, Lydia ; Schmidt, Oliver ; Drake, Harold L.:
Protein- and RNA-Enhanced Fermentation by Gut Microbiota of the Earthworm Lumbricus terrestris.
In: Applied and Environmental Microbiology.
Bd. 84
(2018)
Heft 11
.
- e00657-18.
ISSN 1098-5336
DOI: https://doi.org/10.1128/AEM.00657-18
Abstract
Earthworms are a dominant macro-fauna in soil ecosystems and have determinative effects on soil fertility and plant growth. These invertebrates feed on ingested material, and gizzard-linked disruption of ingested fungal and bacterial cells is conceived to provide diverse biopolymers in the anoxic alimentary canal of earthworms. Fermentation in the gut is likely important to the utilization of ingested biopolymer-derived compounds by the earthworm. This study therefore examined the fermentative response of gut content-associated microbes of the model earthworm Lumbricus terrestris to (a) microbial cell-lysate (to simulate gizzard-disrupted cells) and (b) dominate biopolymers of such biomass, protein and RNA. The microbial cell-lysate augmented the production of H₂, CO₂, and diverse fatty acids (e.g., formate, acetate, propionate, succinate, and butyrate) in anoxic gut content microcosms, indicating that the cell-lysate triggered diverse fermentations. Protein and RNA also augmented diverse fermentations in anoxic microcosms of gut contents, each yielding a distinct product profile (e.g., RNA yielded H2 and succinate whereas protein did not). The combined product profile of protein and RNA treatments was similar to that of cell-lysate treatments, and 16S rRNA-based analyses indicated that many taxa that responded to cell-lysate were similar to taxa that responded to protein or RNA. In particular, protein stimulated Peptostreptococcaceae, Clostridiaceae, and Fusobacteriaceae, whereas RNA stimulated Aeromonadaceae. These findings demonstrated the capacity of gut-associated obligate anaerobes and facultative aerobes to catalyze biopolymer-driven fermentations, and highlight the potential importance of protein and RNA as substrates linked to the overall turnover dynamics of organic carbon in the alimentary canal of the earthworm.