Single-cell visualization and quantification of trace metals in Chlamydomonas lysosome-related organelles.
Stefan SchmollingerSi ChenDaniela StrenkertColleen HuiMartina RalleSabeeha S MerchantPublished in: Proceedings of the National Academy of Sciences of the United States of America (2021)
The acidocalcisome is an acidic organelle in the cytosol of eukaryotes, defined by its low pH and high calcium and polyphosphate content. It is visualized as an electron-dense object by transmission electron microscopy (TEM) or described with mass spectrometry (MS)-based imaging techniques or multimodal X-ray fluorescence microscopy (XFM) based on its unique elemental composition. Compared with MS-based imaging techniques, XFM offers the additional advantage of absolute quantification of trace metal content, since sectioning of the cell is not required and metabolic states can be preserved rapidly by either vitrification or chemical fixation. We employed XFM in Chlamydomonas reinhardtii to determine single-cell and organelle trace metal quotas within algal cells in situations of trace metal overaccumulation (Fe and Cu). We found up to 70% of the cellular Cu and 80% of Fe sequestered in acidocalcisomes in these conditions and identified two distinct populations of acidocalcisomes, defined by their unique trace elemental makeup. We utilized the vtc1 mutant, defective in polyphosphate synthesis and failing to accumulate Ca, to show that Fe sequestration is not dependent on either. Finally, quantitation of the Fe and Cu contents of individual cells and compartments via XFM, over a range of cellular metal quotas created by nutritional and genetic perturbations, indicated excellent correlation with bulk data from corresponding cell cultures, establishing a framework to distinguish the nutritional status of single cells.
Keyphrases
- single cell
- mass spectrometry
- induced apoptosis
- high resolution
- electron microscopy
- cell cycle arrest
- metal organic framework
- heavy metals
- ms ms
- aqueous solution
- high throughput
- multiple sclerosis
- single molecule
- stem cells
- cell therapy
- high performance liquid chromatography
- endoplasmic reticulum stress
- electronic health record
- gene expression
- oxidative stress
- big data
- machine learning
- dna methylation
- minimally invasive
- gas chromatography
- health risk
- photodynamic therapy
- optical coherence tomography
- fluorescence imaging
- pi k akt
- living cells
- high speed