In this supplement we present a scheme of the setup used for the preparation of samples by the differential drying technique (DDT) and original TEM images from which we deduced the sketches of organic fine structures shown in the paper on
Figure 3a. Additional overview images at different resolution show the simultaneous occurrence of distinct organic structures. The resolution down to the macromolecular level is documented.
Figure 1.
Schematic diagrams of the setup for preparation of high molecular weight organic matter (HMW-OM) on an ultrathin carbon support film (thickness 2-3 nm) by a differential drying technique (DDT) for TEM analysis. The HMW-OM was produced from dissolved organic matter (DOM) present in sterile filtered, Na
N
3-preserved River
Elbe water during abiotic incubations by aggregation. I: Sketches of the organic structures detected in the different regions described in II.
In region 1 mainly spherical colloids (1a, c) and chains of small colloids (1b) were detected. In region 2 mainly filaments (2a) and filaments with globular particles attached to these were found (2 b,c). Region 3 contained mainly agglomerations of densely packed straight filaments. In region 4 micelle-like microparticles between 0,4-
0,8 µm in diameter dominated. Region 5 included all the remains producing a mixture of dense material. It should be mentioned that the structures dominant in region 1 were also present in all other regions, coexisting with the respective other structures described above for regions 2-5 which in return were practically absent in region 1.
II.: Upper view of the setup for preparation by DDT. Organic matter of different structure and density accumulated on the carbon support film at different regions (1-
5), which emerged along the gas flow.
III. Side view of the setup for preparation by DDT. It consists of a TEM grid covered by an ultrathin carbon support film, which was made hydrophilic by glow discharge.
For HMW-
OM preparation 0,6 µl of the whole mount water sample was applied onto the carbon film as a thin layer. The layer was dried with a mild flow of moistened pure
N2 gas, directed with a flattened pipette tip in parallel to the grid surface. The drying process was continuously observed with a binocular and was continued until no reflections of a water layer could be detected.
Figure 2.
TEM images of the high molecular weight organic matter (HMW-OM) present in sterile filtered, Na
N
3-preserved River Elbe water after abiotic aggregation prepared for TEM analysis by DDT and selectively enriched in region 1 of the carbon support film as described in Figure 1 (I.1a-c). (a) Overview showing that globular colloids were dominant with a background free of any other structures. (b) Fine structure of the singular globular colloids. No fibrillar substructures were present. (c) Fine structure of chains of globular colloids attached to each other without filaments associated.
Figure 3.
TEM images of the high molecular weight organic matter (HMW-OM) present in sterile filtered, Na
N
3-preserved River Elbe water after abiotic aggregation prepared for TEM analysis by DDT and enriched in region 2 of the carbon support film as described in Figure 1 (I. 2a-c). (a) Overview of the filamentous matter present. In the right upper corner a filamentous cluster can be seen. In addition, very fine pure single filaments and in the right lower corner filaments partly associated with globular

colloids are shown. The image indicates that different types of filaments can occur separately from each other in natural waters. (b) Fine structure of filaments free of larger attachments. (c) Fine structure of a filament with attachments. (d) Fine structure of a cluster of filaments with attachments. (e) A short filament with globular inclusions, visualizing macromolecular structure at high resolution without a stain. As background the structure of the carbon film becomes visible at a magnification x
200.000.
Figure 4.
TEM image of the high molecular weight organic matter (HMW-OM) present in sterile filtered, Na
N
3-preserved River Elbe water after abiotic aggregation prepared for TEM analysis by DDT and enriched in region 3 of the carbon support film as described in
Figure 1 (I. 3a). Densely packed straight filaments accompanied by globular colloids are shown.
Figure 5.
TEM image of the high molecular weight organic matter (HMW-OM) present in sterile filtered, Na
N
3-preserved River Elbe water after abiotic aggregation prepared for TEM analysis by DDT and enriched in region 4 of the carbon support film as described in
Figure 1 (I. 4a,b). The image shows mainly singular micelle-like microparticles in the absence of any remains.
Figure 6.
TEM image of the high molecular weight organic matter (HMW-OM) present in sterile filtered, Na
N
3-preserved River Elbe water after abiotic aggregation prepared for TEM analysis by DDT and enriched in region 5 of the carbon support film as described in
Figure 1. The overview resolves both smaller components and large networks in one image. Because this image was taken at the outer edge of the support, it includes all remains, which were not separated by DDT.
Figure 7.
TEM image of the high molecular weight organic matter (HMW-OM) present in sterile filtered, Na
N
3-preserved River Elbe water after abiotic aggregation and prepared for
TEM analysis by a non-directed d rying of a whole mount water sample of 1 µl applied to an ultrathin carbon support as a single drop in a wet chamber (WMDT). Micelle-like microparticles can be seen in the lower part of the image that represents the outer edge of one of the drying spots. The microparticles were quite similar to those found in region 4 after preparation using DDT (see Figure 5). This gives evidence that the microparticles were not produced as an artifact during the DDT preparation. On the upper part of the image the densely packed straight filaments (see Figure 4) and the globular colloids (see Figure 2) found in region 3 and 1 after DDT preparation, respectively, can be seen. Beam damages, which occur during TEM analysis of thicker layers, can be seen at the lower end of the upper part of the image.