Epigeic earthworms exert a bottleneck effect on microbial communities through gut associated processes

Area of Science:

• Ecology
• Soil Science
• Microbiology

Background:

• Earthworms are crucial for organic matter decomposition through interactions with microorganisms.
• The direct effects of earthworm gut processes on microbial communities, especially in epigeic species in human-altered environments, are not fully understood.
• Eisenia andrei's role in modifying fresh organic matter's microbiological properties via gut processes requires further investigation.

Purpose of the Study:

• To determine how the earthworm Eisenia andrei alters the microbiological properties of fresh organic matter through gut processes.
• To assess if these direct effects are influenced by the earthworm's diet.
• To investigate the impact of earthworm digestion on microbial community structure and activity.

Main Methods:

• Analyzing microbial community structure using phospholipid fatty acid profiles.
• Measuring microbial activity via fluorescein diacetate hydrolysis.
• Examining earthworm casts from cow, horse, and pig manure with distinct microbial compositions.

Main Results:

• Earthworm gut passage reduced total microbial biomass and bacterial biomass across all manure types, leaving fungal biomass unaffected.
• Microbial activity showed no reduction in casts from pig manure, unlike biomass reductions observed elsewhere.
• No significant differences in microbial community structure were found in casts from different manures, indicating a digestive bottleneck effect.

Conclusions:

• The earthworm gut acts as a significant modulator of microbial communities.
• Digestion favors a reduced yet more active microbial population in egested materials (casts).
• Understanding these biotic interactions is vital for comprehending nutrient cycling within decomposer food webs.