Bright field scanning tem stem module

The samples for nanoscale elemental analysis in analytical TEM using energy-dispersive X-ray spectroscopy (EDX) were prepared as described previously [29 (link)]: fixed, dehydrated, and embedded in araldite as described above except the staining with lead citrate. Semi-thin sections were made with Leica EM UC7 ultratome (Leica Microsystems, Wien, Germany) and examined under a JEM-2100 (JEOL, Japan) microscope equipped with a LaB₆ gun at the accelerating voltage of 200 kV. Point EDX spectra were recorded using a JEOL bright-field scanning TEM (STEM) module and X-Max X-ray detector system with an ultrathin window capable of analysis of light elements starting from boron (Oxford Instruments, Abingdon, UK). The energy range of recorded spectra was 0–10 keV with a resolution of 10 eV per channel. At least 10 cells per specimen were analyzed. Spectra were recorded from different parts of electron-dense inclusions and from other (sub)compartments of microalgae cells. Spectra were processed with INKA software (Oxford instruments, Abingdon, UK) and presented in the range of 0.1–4 keV.

Cells for TEM were harvested from approximately 5-ml culture aliquots. The fixation, dehydration, embedding, and staining procedures were described by Kokabi et al. (2019) (link). Ultra-thin sections (60–90 nm) were observed and imaged under an FEI Tecnai 12 (FEI, OR, United States) or a JEM-1011 (JEOL, Tokyo, Japan) transmission electron microscope (TEM) for the ultrastructural analysis.
The samples for nanoscale elemental analysis in analytical TEM using EDX were fixed, dehydrated, and embedded in araldite (Electron Microscopy Sciences, United States) as described above. Ultra-thin sections for energy-dispersive X-ray spectroscopy (EDX) analysis were examined under a JEM-2100 (JEOL, Tokyo, Japan) microscope equipped with a LaB₆ gun at the accelerating voltage of 200 kV. Point EDX spectra were recorded using a JEOL bright-field scanning TEM (STEM) module and an X-Max X-ray detector system with an ultra-thin window, capable of analyzing light elements, starting from boron (Oxford Instruments, High Wycombe, UK). The energy range of the recorded spectra was 0–10 keV with a resolution of 10 eV per channel. Spectra were background-corrected and further processed with INKA software (Oxford Instruments). Quantitative morphometric analysis of TEM micrographs was performed using Zen software (Carl Zeiss Microscopy GmbH).