Juanfang Ruan a,1, Takayuki Kato a,1, Claire-Lise Santini b, Tomoko Miyata a, Akihiro Kawamoto a, Wei-Jia Zhang b, Alain Bernadac c, Long-Fei Wu b, and Keiichi Namba a,d,2
aGraduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan;
bLaboratoire de Chimie Bactérienne, Unité Mixte de Recherche 7283, Aix-Marseille Université, Centre National de la Recherche Scientifique, F-13402, Marseille Cedex 20, France;
cService de Microscopie, Aix-Marseille Université, Institut de Microbiologie de la Méditerranée-Centre National de la Recherche Scientifique, F-13402, Marseille Cedex 20, France; and
dRiken Quantitative Biology Center, Suita, Osaka 565-0871, Japan
Edited by Howard C. Berg, Harvard University, Cambridge, MA, and approved November 2, 2012 (received for review September 2, 2012)
The bacterial flagellum is a motility organelle that consists of a rotary motor and a helical propeller. The flagella usually work individually or by forming a loose bundle to produce thrust. However, the flagellar apparatus of marine bacterium MO-1 is a tight bundle of seven flagellar filaments enveloped in a sheath, and it has been a mystery as to how the flagella rotate smoothly in coordination. Here we have used electron cryotomography to visualize the 3D architecture of the sheathed flagella. The seven filaments are enveloped with 24 fibrils in the sheath, and their basal bodies are arranged in an intertwined hexagonal array similar to the thick and thin filaments of vertebrate skeletal muscles. This complex and exquisite architecture strongly suggests that the fibrils counter-rotate between flagella in direct contact to minimize the friction of high-speed rotation of individual flagella in the tight bundle within the sheath to enable MO-1 cells to swim at about 300 µm/s.
flagellar basal body magnetotactic motility
1J.R. and T.K. contributed equally to this work.
2To whom correspondence should be addressed. E-mail: firstname.lastname@example.org.
Author contributions: L.-F.W. and K.N. designed research; J.R., T.K., T.M., and A.K. performed research; C.-L.S., T.M., A.K., W.-J.Z., and A.B. contributed new reagents/analytic tools; J.R., T.K., and K.N. analyzed data; and J.R., T.K., and K.N. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
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NOTA DESTE BLOGGER:
Como explicar, por etapas gradualistas darwinistas, a origem e evolução de uma bactéria que tem um pacote flagelar de sete motores magneticamente guiado e acionado por 24 engrenagens, e que vai de 0 a 300 micrômetros em um segundo, dez vezes mais rápido do que E. coli? Explica aí, Darwin!