Time lapse synchrotron IR chemical imaging for observing the acclimation of a single algal cell to CO2 treatment

Abstract

Algae are the main primary producers in aquatic environments and therefore of fundamental importance for the global ecosystem. Mid-infrared (IR) microspectroscopy is a non-invasive tool that allows in principle studying chemical composition on a single-cell level. For a long time, however, mid-infrared (IR) imaging of living algal cells in an aqueous environment has been a challenge due to the strong IR absorption of water. In this study, we employed multi-beam synchrotron radiation to measure time-resolved IR hyperspectral images of individual Thalassiosira weissflogii cells in water in the course of acclimation to an abrupt change of CO2 availability (from 390 to 5000 ppm and vice versa) over 75 min. We used a previously developed algorithm to correct sinusoidal interference fringes from IR hyperspectral imaging data. After preprocessing and fringe correction of the hyperspectral data, principal component analysis (PCA) was performed to assess the spatial distribution of organic pools within the algal cells. Through the analysis of 200,000 spectra, we were able to identify compositional modifications associated with CO2 treatment. PCA revealed changes in the carbohydrate pool (1200–950 cm$$^{-1}$$ - 1 ), lipids (1740, 2852, 2922 cm$$^{-1}$$ - 1 ), and nucleic acid (1160 and 1201 cm$$^{-1}$$ - 1 ) as the major response of exposure to elevated CO2 concentrations. Our results show a local metabolism response to this external perturbation.

Seeing plants as never before

“…Similar approach was applied using Raman imaging (Shen et al ., 2019). A limitation of Raman spectroscopy is that the cross‐sections are small, whereas the MIR platform (Shi et al ., 2020) has the capacity to provide metabolic images covering an entire tissue or even organ; (4) the growing focus on single cell analysis and small volume environments favors the deployment of IR imaging, which has already been used to good effect to reveal the metabolic dynamics of isolated plant (Azarfar et al ., 2021) and animal (Carnevali et al ., 2019) cells. Attenuated Total Reflection–FTIR imaging in particular offers a detection methodology able to reveal the composition of fluids, allowing it to be used to study many processes involving microfluidics, ranging from reactions to separations (Chan et al ., 2009); (5) conventionally, identifying and quantifying the components present in natural products rely on extraction/separation techniques such as chromatography/MS.…”

Synchrotron FTIR Microspectroscopy Investigations on Biochemical Changes Occurring in Human Cells Exposed to Proton Beams

“…The enormous potentialities of SR-µFTIR spectroscopy in examining cell samples exposed to different external agents have been largely exploited in various experimental conditions [6][7][8][9][10][11][12].…”

“…This enables the acquisition of high-quality single cell spectra even in an aqueous environment [4][5][6]. These characteristics have been largely exploited for investigating cellular systems in different experimental conditions [7][8][9][10][11][12].…”