Supra 55 scanning electron microscope

The morphology images were recorded on Zeiss SUPRA55 scanning electron microscope (SEM), which combined with energy‐dispersive X‐ray spectroscopy (EDX), and transmission electron microscopy (TEM) (Philips Tecnai 20 and JEOL JEM‐2010 high‐resolution TEM). The optical image was performed on a Leica DMI8 fluorescence microscope. X‐ray diffraction (XRD) data were performed on Shimadzu XRD‐6000 X‐ray diffractometer (Cu Kα radiation (0.154 nm) at 40 kV, 30 mA, and scanning rate of 10° min⁻¹). X‐ray photoelectron spectra (XPS) were performed on a Thermo VG ESCALAB 250 X‐ray photoelectron spectrometer (pressure: 2 × 10^–9 Pa; excitation source: Al Kα X‐rays). The aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) was performed on FEI Titan Cubed Themis G3 300. The Co K‐edge XAS data were collected at the beamline 1W1B of the Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics (IHEP), and Chinese Academy of Sciences (CAS). Contact angle was performed by the sessile drop method in glove box. Crimping and shocking tests were carried out by tablet press (MTI, China) and vortex mixer (TAT, China).

We employed SEM and TEM for further observation of the morphology, especially for K. kristinae_LC. The original bacterial culture of the strain was centrifuged (12,000 rpm for 2 min), and the supernatant was removed. The harvested cells were washed three times with 0.1 M phosphate buffer (pH 7.2), and then fixed in 2.5% glutaraldehyde solution (SINOPHARM, China) at 4°C overnight. Subsequently, the bacteria were dehydrated in a graded ethanol solution (SINOPHARM, China), dried at the critical point of CO₂, mounted on metal stubs, coated with gold, and observed under a Zeiss Supra^™ 55 scanning electron microscope for morphology observation. Bacterial cells were fixed overnight with 2.5% glutaraldehyde at 4°C. After washing with PBS three times, the samples were fixed with 1% osmic acid for 2 h. Then, the cells were washed with PBS three times, and dehydrated sequentially in ethanol at gradient concentrations (50, 70, and 90%) for 5 min at each gradient. Next, the cells were rinsed in 100% ethanol twice for 7 min. After dehydration, the cells were embedded in a resin at 25°C for 4 h. After polymerization at 65°C for 48 h, the samples were sliced and stained with uranyl acetate for 20 min, followed by alkaline lead citrate for 10 min. Finally, the prepared cells were observed under a transmission electron microscope (Hitachi HT-7800, Japan).