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Symbiotic Bacteria Associated with Stomach Discs of Human Lice

Lice & Disease


Appl Environ Microbiol. 2006 November; 72(11): 7349–7352.
Published online 2006 September 1. doi: 10.1128/AEM.01429-06.
Copyright © 2006, American Society for Microbiology

Kayoko Sasaki-Fukatsu,1 Ryuichi Koga,1 Naruo Nikoh,2 Kazunori Yoshizawa,3 Shinji Kasai,4 Minoru Mihara,5 Mutsuo Kobayashi,4 Takashi Tomita,4 and Takema Fukatsu1*
Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566,1 Division of Natural Sciences, University of the Air, Chiba 261-8586,2 Department of Ecology and Systematics, Hokkaido University, Sapporo 060-8589,3 Department of Medical Entomology, National Institute of Infectious Diseases, Tokyo 162-8640,4 Department of Environmental Biology, Japan Environmental Sanitation Center, Kawasaki 210-0828, Japan5
*Corresponding author. Mailing address: National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566, Japan. Phone: 81-29-861-6087. Fax: 81-29-861-6080. E-mail:
Received June 21, 2006; Accepted August 16, 2006.


The symbiotic bacteria associated with the stomach disc, a large aggregate of bacteriocytes on the ventral side of the midgut, of human body and head lice were characterized. Molecular phylogenetic analysis of 16S rRNA gene sequences showed that the symbionts formed a distinct and well-defined clade in the Gammaproteobacteria. The sequences exhibited AT-biased nucleotide composition and accelerated molecular evolution. In situ hybridization revealed that in nymphs and adult males, the symbiont was localized in the stomach disc, while in adult females, the symbiont was not in the stomach disc but in the lateral oviducts and the posterior pole of the oocytes due to female-specific symbiont migration. We propose the designation “Candidatus Riesia pediculicola” for the louse symbionts. Read more>>>


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