Allying with armored snails: the complete genome of gammaproteobacterial endosymbiont.
Deep-sea vents harbor dense populations of various animals that have their specific symbiotic bacteria. Scaly-foot gastropods, which are snails with mineralized scales covering the sides of its foot, have a gammaproteobacterial endosymbiont in their enlarged esophageal glands and diverse epibionts on the surface of their scales. In this study, we report the complete genome sequencing of gammaproteobacterial endosymbiont. The endosymbiont genome displays features consistent with ongoing genome reduction such as large proportions of pseudogenes and insertion elements. The genome encodes functions commonly found in deep-sea vent chemoautotrophs such as sulfur oxidation and carbon fixation. Stable carbon isotope ((13)C)-labeling experiments confirmed the endosymbiont chemoautotrophy. The genome also includes an intact hydrogenase gene cluster that potentially has been horizontally transferred from phylogenetically distant bacteria. Notable findings include the presence and transcription of genes for flagellar assembly, through which proteins are potentially exported from bacterium to the host. Symbionts of snail individuals exhibited extreme genetic homogeneity, showing only two synonymous changes in 19 different genes (13 810 positions in total) determined for 32 individual gastropods collected from a single colony at one time. The extremely low genetic individuality in endosymbionts probably reflects that the stringent symbiont selection by host prevents the random genetic drift in the small population of horizontally transmitted symbiont. This study is the first complete genome analysis of gastropod endosymbiont and offers an opportunity to study genome evolution in a recently evolved endosymbiont.
1] Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan [2] Subsurface Geobiology Advanced Research (SUGAR) Project, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
Satoshi
S
Nakagawa
Subsurface Geobiology Advanced Research (SUGAR) Project, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
Shigeru
S
Shimamura
Cooperative Research Project for Extremophiles, Institute of Biogeosciences, JAMSTEC, Yokosuka, Japan.
Yoshihiro
Y
Takaki
Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Tokyo, Japan.
Yohey
Y
Suzuki
Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Shun-ichi
S
Murakami
Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Tamaki
T
Watanabe
Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
So
S
Fujiyoshi
Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Sayaka
S
Mino
Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Tomoo
T
Sawabe
1] Laboratory of Advanced Chemical Biology, Graduate School of Life Science, Hokkaido University, Sapporo, Japan [2] Amino Up Chemical Company, Sapporo, Japan.
Takahiro
T
Maeda
Subsurface Geobiology Advanced Research (SUGAR) Project, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
Hiroko
H
Makita
Enoshima Aquarium, Fujisawa, Japan.
Suguru
S
Nemoto
1] Laboratory of Advanced Chemical Biology, Graduate School of Life Science, Hokkaido University, Sapporo, Japan [2] Medicinal Chemistry Pharmaceuticals, Co. Ltd., Sapporo, Japan.
Shin-Ichiro
S
Nishimura
Marine Biodiversity Research Program, JAMSTEC, Yokosuka, Japan.
Hiromi
H
Watanabe
Subsurface Geobiology Advanced Research (SUGAR) Project, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
Tomo-o
TO
Watsuji
Subsurface Geobiology Advanced Research (SUGAR) Project, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
Ken
K
Takai
D000818:Animals; D002247:Carbon Isotopes / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics; D005407:Flagella / Q000235:genetics; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014644:Genetic Variation; D016680:Genome, Bacterial / Q000235:genetics*; D060086:Hydrothermal Vents; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D012908:Snails / Q000382:microbiology*; D013559:Symbiosis
D002247:Carbon Isotopes; D004251:DNA Transposable Elements