Matrix‐free single‐cell LDI‐MS investigations of the diatoms Coscinodiscus granii and Thalassiosira pseudonana

Abstract

Single-cell investigations of the diatoms Coscinodsicus granii and Thalassiosira pseudonana were performed using laser desorption/ionization (LDI)-MS without the addition of chemical matrices. The unique cell wall architecture of these microalgae, more precisely the biomineralized nanostructured surface, supported the ionization of cellular as well as surface-related metabolites. In model experiments with purified diatom cell walls of eight species C. granii and T. pseudonana proved to promote the ionization of the polymer polyethylene glycol most efficiently. These species were therefore chosen for further experiments. Without any additional workup, living diatom cells can be washed, can be placed on the LDI target and can immediately be profiled using LDI-MS. Characteristic signals arising from the two species were assigned to common metabolites known from diatom metabolism. Among others, chlorophyll, phospholipids and amino acids were detected. Using these fingerprint signals, we were able to perform species-specific MS imaging down to a single-cell resolution of 20 by 20 µm. The larger C. granii cells can be directly visualized, while more than one of the smaller T. pseudonana cells is needed to generate high-quality images. The introduced technique will pave the way toward a chemotyping of phytoplankton that will enable the automated annotation of microalgal species. But also, an assignment of metabolic plasticity on a single-cell level that could answer fundamental questions about plankton diversity is now in reach.

Single‐Cell Mass Spectrometry Approaches to Explore Cellular Heterogeneity

“…[75][76][77] In some cases,i ti sp ossible to use native cellular constituents as the matrix. [78] An important objective in single-cell analysis by MALDI-MS is to enhance the throughput. Microarrays for MS (MAMS), comprised of arrays of hydrophilic micro-wells patterned on ao mniphobic surface,s hows promise for the rapid analysis of up to 169 cells.…”

Einzelzell‐Massenspektrometrie zur Untersuchung zellulärer Heterogenität

“…Diese Analyse kann im Zusammenhang mit der hoch ortsauflösenden MS‐Bildgebung für in Gewebe eingebettete Zellen oder der lokalen MS‐Analyse für einzellige Organismen und aus Geweben abgetrennte Zellen durchgeführt werden. In einigen Fällen besteht die Möglichkeit, natürliche Zellbestandteile als Matrix zu verwenden …”

Identification to species level of live single microalgal cells from plankton samples with matrix-free laser/desorption ionization mass spectrometry

“…Single-cell analysis has been introduced in the last decade to profile the cellular content, providing information on the genes, proteome, transcriptome or metabolome of the organism under study (Yuan et al 2017). Single-cell mass spectrometry of algal cells has already been developed with matrix-free laser desorption-ionization using the ionization-enhancing effect of diatom cell walls (Jaschinski et al 2014). Live single-cell mass spectrometry (LSC-MS) with laser-desorption ionization high-resolution mass spectrometry was developed to profile reliably the low-molecular-weight metabolites of living cells kept in their native environment prior to analysis.…”