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, 72 (11), 7349-52

Symbiotic Bacteria Associated With Stomach Discs of Human Lice

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Symbiotic Bacteria Associated With Stomach Discs of Human Lice

Kayoko Sasaki-Fukatsu et al. Appl Environ Microbiol.

Abstract

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.

Figures

FIG. 1.
FIG. 1.
Whole-mount in situ hybridization of symbiotic bacteria in human body lice. (A) A first-instar nymph with a large round stomach disc at the center of the ventral abdomen. The symbiont cells are specifically detected in the stomach disc. (B) An enlarged image of the stomach disc. The location of the symbiont cells exhibited radial compartment-like structures. (C) An adult male, in which the symbiont is localized in the stomach disc. (D) An adult female, in which the symbiont is not detected in the stomach disc but in the lateral oviducts and the posterior poles of oocytes. (E) An enlarged image of the female reproductive organs. (F) An enlarged image of an oocyte. The arrows and arrowheads indicate the lateral oviducts and the posterior poles of oocytes, respectively.
FIG. 2.
FIG. 2.
Molecular phylogenetic analysis of 16S rRNA gene sequences of the stomach disc symbionts from human lice. A neighbor-joining tree is shown; maximum-parsimony analysis gave essentially the same result (data not shown). Bootstrap values higher than 70% are shown at the nodes. In brackets are sequence accession numbers.

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