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Applied and Environmental Microbiology, January 2006, p. 769-775, Vol. 72, No. 1
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.1.769-775.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Transmission of Nephridial Bacteria of the Earthworm Eisenia fetida

Seana K. Davidson* and David A. Stahl

Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington 98195-2700

Received 27 July 2005/ Accepted 28 September 2005

The lumbricid earthworms (annelid family Lumbricidae) harbor gram-negative bacteria in their excretory organs, the nephridia. Comparative 16S rRNA gene sequencing of bacteria associated with the nephridia of several earthworm species has shown that each species of worm harbors a distinct bacterial species and that the bacteria from different species form a monophyletic cluster within the genus Acidovorax, suggesting that there is a specific association resulting from radiation from a common bacterial ancestor. Previous microscopy and culture studies revealed the presence of bacteria within the egg capsules and on the surface of embryos but did not demonstrate that the bacteria within the egg capsule were the same bacteria that colonized the nephridia. We present evidence, based on curing experiments, in situ hybridizations with Acidovorax-specific probes, and 16S rRNA gene sequence analysis, that the egg capsules contain high numbers of the bacterial symbiont and that juveniles are colonized during development within the egg capsule. Studies exposing aposymbiotic hatchlings to colonized adults and their bedding material suggested that juvenile earthworms do not readily acquire bacteria from the soil after hatching but must be colonized during development by bacteria deposited in the egg capsule. Whether this is due to the developmental stage of the host or the physiological state of the symbiont remains to be investigated.

* Corresponding author. Mailing address: Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195-2700. Phone: (206) 685-3463. Fax: (206) 685-9185. E-mail: skdavid{at}u.washington.edu

Applied and Environmental Microbiology, January 2006, p. 769-775, Vol. 72, No. 1
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.1.769-775.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Pinel, N., Davidson, S. K., Stahl, D. A. (2008). Verminephrobacter eiseniae gen. nov., sp. nov., a nephridial symbiont of the earthworm Eisenia foetida (Savigny). Int. J. Syst. Evol. Microbiol. 58: 2147-2157 [Abstract] [Full Text]  
  • Pernice, M., Wetzel, S., Gros, O., Boucher-Rodoni, R., Dubilier, N. (2007). Enigmatic dual symbiosis in the excretory organ of Nautilus macromphalus (Cephalopoda: Nautiloidea). Proc R Soc B 274: 1143-1152 [Abstract] [Full Text]  


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