Fig. 4

Comprehensive analysis of individual HBY31 cells via confocal Raman spectroscopy. a Confocal imaging enables depth profiling showing the distribution of selected components. The depth profiling was done with a step size of 300 nm. The distribution of Organic matter is demonstrated on the basis of integration of bands in the range 3050–2800 cm⁻¹ and visualises the cell. The integration of the band at 1444 cm⁻¹ enables us to visualise LBs. As can be seen, the LBs’ signals are present only within selected layers, corresponding to the inside of cell. b–f Distribution of selected components in a cell with polyphosphate vacuole, on the basis of integration of bands at: (b) 3050–2800 cm⁻¹ (‘Organic matter’), (c) 1444 cm⁻¹ (‘Lipids’), (d) 2925 cm⁻¹ (‘Proteins’), (e) 753 cm⁻¹ (‘heme’), (e) 1160 cm⁻¹ (‘Polyphosphate’). g, h Cluster analysis results obtained for the cell presented in (b–f): (g) distribution of classes and (h) corresponding spectra of each class with marked selected bands. Size of the imaged area: (a) 5.32 × 5. 24 µm and (b) 5.22 × 5.17 µm. With the use of 532 nm excitation wavelength the theoretical thickness of each plane, according to Rayleigh criterion, is 361 nm