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, Red arrows correlate the MMPs on SEM micrographs with those specifically 642 hybridized in FISH insets. The images on the right panel of every set are the amplification of 643 the images from the left panel. Scale bars: 5?m in A, in FISH insets, EUB338 and yellow color shows the MMPs hybridized with both the green universal probe 640 and the 5'-Cy3-labeled specific probes (SF-5

, Phylogenetic tree of currently identified MMPs. The species in red are newly identified 648 in this study. The unicellular magnetotactic bacteria Desulfamplus magnetomortis and 649

, Desulfovibrio magneticus were used as outgroup references. The trees were constructed 650 based on neighbor-joining analysis. Bootstrap values at the nodes are percentages of 1,000 651 replicates. The scale bar indicates 2% sequence divergence. The GenBank accession numbers 652 of the sequences are given in parentheses. (B) Phylogenetic tree shows the approximate 653 evolutionary position of MMPs with respect to myxobacteria, p.654

, The branch length of cyanobacteria is 655 truncated. All orders of Deltaproteobacteria are presented, including the unicellular 656 magnetotactic bacteria, pink), and cyanobacteria

. Stem-haadf, Scan-TEM high-angle annular dark-field) mode (A, B and D) and TEM-661 bright field (BF) mode (G to K) micrographs of ultrathin sections of HPF/FS-fixed ellipsoidal 662

. Mmps, C) and (E) are, respectively, a center stack or reconstitution of laser confocal images 663 34 of ellipsoidal MMPs; the membrane is stained by FM4-64 (red) and DNA by DAPI (blue, p.664

, (F) shows a high-resolution image of a representative bullet-665 shaped magnetosome of ellipsoidal MMPs. From the corresponding fast Fourier transform 666 (inset), it can de deduced that the magnetite elongation direction is <110> and that a 667 prominent {111} basal plane is also visible

, White arrows point 670 to the magnetosomes and the (f) is a fence-like structure. The yellow triangles indicate the 671 extremity of the growing septa in cells 5 and 6. (H) is a magnified image of cell 2 showing 672 the periphery structure that consists of flagella, The yellow arrows visualize the dashed line on the surface of the MMP and the red and 669 yellow asterisks indicate the outer and the inner membrane, respectively

, It visualizes the fence-like structure (f) and a periphery bar (green arrow). (K) is a 677 magnified view of the core lumen (CL) on another successive slice of (G) with vesicles 678 (black arrows) and filaments

, are Nil red-stainable lipid granules

, Scale bars: 1 µm in A, C, and G, 500 nm in B, D, and E, Experimental Procedures), p.35

H. Images, The insets in A to D and G illustrate the estimated cut direction of the 682 corresponding sections

, Figure 4. Division of constituent cells and reproduction of MMPs

, A) is a SEM micrograph of a dividing MMP. Chemically (B) and HPF/FS-(C) fixed

, ultrathin sections show the unilateral indentation of cell outer membranes (red asterisks and 687 yellow triangles). (D) and (E) are two successive slices each of approximately 75 nm. The 688 cell on the two slices is indicated with 5 and 5

. 3. Fig, E2) and (E3) are magnified images of (E1) to show the end (yellow triangles) of the 690 outer membrane (red asterisks) indentation. The yellow arrows (in D, E and F) visualize the 691 dashed line on the surface of the MMP. The red, yellow and blue asterisks indicate the outer 692 and inner membranes, and the peptidoglycan layer

B. , C. , G. , H. , and I. , and (J) are fluorescence confocal microscope images that show indentation of cell 694 membranes of individual cells (yellow arrows in G) and division of a MMP (yellow 695 triangles). (H) is a HPF/FS slice. DAPI staining (G, I, and J) was used to visualize 696 chromosomes (blue spots), FM-4-64 (G and I, red) to visualize membranes and Nil red (J, 697 red) to visualize lipids. Scale bars: 1 µm in A

, Micrograph of scanning transmission electron microscope in high-angle annular dark-703 field mode (STEM-HAADF) shows the aligned magnetosome chains along the long axis of 704 38 the ellipsoidal MMP. (B) SEM micrograph reveals flagella on the surface of MMPs, p.705

, showcases the escape backward (red track) and return north-seeking forward, p.706

, and (E) show representative swimming behaviors when MMPs confronted 708 obstacles or displayed axial magnetotaxis, respectively. Reversal of swimming direction to 709 south-seeking is indicated by arrows "r" and red tracks. (F) shows a north-seeking MMP 710 (green track) changing its swimming direction in response to the reversal of the alternate 711 uniform magnetic field (10 Gs, 0.5 Hz). After 0.2 second it abruptly reversed its swimming 712 direction to south-seeking (arrow "r" and red track) with acceleration (ac) and continued a 713 south-seeking motion out of the UV spot. The movies were recorded at 60 frames per second 714 (fps) for D and E and 30 fps for F, ping-pong swimming behavior (C1) and corresponding velocity (C2, positive is north-707 seeking). (D)