Insights into the earthworm gut multi-kingdom microbial communities

Area of Science:

• Soil ecology
• Microbiology
• Eukaryotic and prokaryotic community analysis

Background:

• Earthworms are crucial soil engineers influencing nutrient cycling and soil microbial communities.
• Earthworm feeding and burrowing activities significantly alter soil microbial assemblages.
• The gut microbiome composition of earthworms remains underexplored.

Purpose of the Study:

• To compare eukaryotic and prokaryotic gut microbiome profiles across different earthworm genera and life forms.
• To assess the significance of earthworm life forms in shaping gut microbial communities.
• To explore cross-kingdom interactions within earthworm guts and identify potential keystone species.

Main Methods:

• Amplicon sequencing of the 16S rRNA gene for bacteria.
• Amplicon sequencing of the 18S rRNA gene for eukaryotes.
• Analysis of gut community assemblages in earthworm species from genera Aporrectodea, Allolobophora, and Lumbricus.

Main Results:

• High eukaryotic diversity found, dominated by SAR supergroup, fungi, and metazoans.
• Bacterial communities were primarily composed of Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, and Verrucomicrocomicrobia.
• Alpha diversity was lowest in Lumbricus herculeus for both eukaryotic and prokaryotic communities.
• Beta diversity analysis revealed earthworm species as a key factor shaping gut microbiomes, with L. herculeus distinct from other species.
• Cross-kingdom networks demonstrated significant interactions between protist and bacterial operational taxonomic units (OTUs).

Conclusions:

• Earthworm gut microbiome composition is significantly influenced by earthworm species and life form.
• Earthworm gut microbiomes comprise complex cross-kingdom interactions between eukaryotes and prokaryotes.
• Lumbricus herculeus harbors a distinct gut microbiome compared to other studied earthworm species.