Fig. 9: EpsA-O in the intercellular space of B. subtilis biofilm.
a The volume space of a single EpsA-O molecule. By combining the data obtained by universal calibration method, intrinsic viscosity and NMR spectroscopy, the EpsA-O molecule was modeled with a String-of-beads model. The representative structure is a symmetrical comb with 0.5 degree of branching and 78 nm radius of gyration. The backbone has a persistence length of 11 nm. The polymer is composed of 12500 impenetrable beads of diameter 0.52 nm corresponding to the size of glucose molecule. b The mature WT biofilms were partially disrupted to obtain a better view into cell fibers composing the 3D structures. Scale bar represents 10 μm. c The volume fraction of intercellular space and the average distance between two neighboring cells were estimated to be (50 ± 10) % and 190 nm, respectively. d In the box of 190 × 190 × 190 nm3, EpsA-O was modeled at concentration slightly above c** (see Fig. 4b); each molecule is in different color. e The same box, but the opposing xz sides, representing the cell envelopes of two neighboring cells, were set to be impenetrable and were the starting points of growing EpsA-O molecules, 10 EpsA-O molecules for each bacterium (red for bacterium 1 and black for bacterium 2) are shown, corresponding to the actual EpsA-O concentration. f xz projection of the space in e, showing the empty space (pores) between bacterium 1 to bacterium 2. g Distribution of pore diameters as determined from five independent projections.
