Movie S1. Escape motility of spherical MMPs.


Fig. S1. Two kinds of sediment in the intertidal zones of the Huiquan Bay. During the sampling at the low tide, there was little water above the sediments. Typically, the ellipsoidal MMPs were only detected in the gravel sediments (red arrow). In the sandy sediments (blue arrow) in our present study, only spherical MMPs were observed.


Fig. S2. Elemental mapping of magnetosomes in spherical MMPs. High angle annular dark field (HAADF) image showing the location of magnetsomes. Elemental maps of iron (B), oxygen (C) and sulfur (D) revealed the iron oxide composition of crystals.


Fig. S3. Fluorescence in situ hybridization analysis. Fluorescence in situ hybridization analysis showing that bacterial probe EUB 338 (A) was hybridized with both spherical MMPs (red arrows) and unicellular bacteria (white arrows), while specific probe M97 (B) was only hybridized with spherical MMPs (red arrows). All cells in a MMP exhibited the hybridization signals (C). Bars = 5 μm in (A) and (B), and 2 μm in (C).


Fig. S4. Vertical variation of temperature, salinity, pH and sulfate concentration. The temperature of the sediment and the pH of the pore water varied little in the vertical direction, with a maximum variation of 1.2°C (core B) and 0.52 (core C) respectively. The salinity, ranging from 14‰ to 29‰, varied greatly from the surface to the deep layers. The sulfate profiles varied greatly among the four sediment cores. In the layers with maximum MMPs, the temperature, pH, salinity and the sulfate concentration were in the range of 16.0–16.4°C, 7.83–7.88, 22.0–29.0‰, 1497–2257 mg l−1 respectively.


Fig. S5. Instruments used for pore water sampling and cell counting.

A. The pore water sampler was revised from Hüttel (1990).

B. The slide with four O-rings for hanging drop observation.


Supplemental text. Formula used to calculate the density of MMPs and unicellular MTB in sediments.

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