Acidovorax-like symbionts in the nephridia of earthworms

Summary Dense accumulations of bacteria in the excretory organs, nephridia, were first described more than 75 years ago in members of the annelid family Lumbricidae (earthworms). These nephridial symbionts were assumed to play a role in the degradation of proteins in the excretory fluid for nitrogen...

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Published in:Environmental microbiology 2003-09, Vol.5 (9), p.804-809
Main Authors: Schramm, Andreas, Davidson, Seana K., Dodsworth, Jeremy A., Drake, Harold L., Stahl, David A., Dubilier, Nicole
Format: Article
Language:English
Subjects:
Animals
Base Sequence
Betaproteobacteria - classification
Betaproteobacteria - genetics
Betaproteobacteria - isolation & purification
Betaproteobacteria - physiology
DNA, Bacterial - isolation & purification
Genes, rRNA
In Situ Hybridization, Fluorescence
Molecular Sequence Data
Nitrogen - metabolism
Oligochaeta - microbiology
Phylogeny
Polymerase Chain Reaction
Polymorphism, Restriction Fragment Length
RNA, Ribosomal, 16S - genetics
Sequence Homology
Space life sciences
Symbiosis
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Summary:Summary Dense accumulations of bacteria in the excretory organs, nephridia, were first described more than 75 years ago in members of the annelid family Lumbricidae (earthworms). These nephridial symbionts were assumed to play a role in the degradation of proteins in the excretory fluid for nitrogen recycling. In the present study, the phylogenetic affiliation of the nephridial bacteria of the earthworms Lumbricus terrestris, Aporrectodea tuberculata, Octolasion lacteum and Eisenia foetida was resolved. The 16S rRNA gene sequences of the symbionts formed a monophyletic cluster within the genus Acidovorax. Similarity between symbiont sequences from different host species was 95.5–97.6%, whereas similarity was> 99% between symbiont sequences from individuals of the same species. Densely packed bacteria were detected in the ampulla of the nephridia by fluorescence in situ hybridization (FISH) using Acidovorax‐specific oligonucleotide probes. No other bacterial cells could be found by FISH, although a few sequences other than Acidovorax had been found by PCR and cloning. These results suggest that the Acidovorax‐earthworm symbiosis is a stable, host‐specific association that has evolved from a common bacterial ancestor. Given the close phylogenetic relationship of the symbionts to proteolytic, free‐living Acidovorax species, they may indeed play a role in protein degradation during nitrogen excretion by earthworms.
ISSN:1462-2912
1462-2920
DOI:10.1046/j.1462-2920.2003.00474.x