Measurements of cell-to-cell gene expression variations can offer insight in areas such as developmental biology, immunology and cancer research. Single-cell gene expression variability can be measured using RNAseq techniques, but other related cell-by-cell insights, such as specific single-cell metabolic differences, can be more difficult to measure. Researchers at Stony Brook University’s School of Marine and Atmospheric Sciences have now identified a method that could allow growth differences between single cells to be more easily analyzed, using a Raman-based spectroscopy technique and stable isotope probing (SIP).
SIP and Raman microspectroscopy were used to track the growth rates of E. coli bacteria grown in a 13C-labeled broth medium. Using the spectral red shifts of Raman-scattered emissions to measure the incorporation of 13C into biomolecules, the researchers could ultimately calculate the growth rates of individual cells. The estimates derived from the SIP-Raman microspectroscopy measurements were confirmed by optical density measurements. This research was published in Applied and Environmental Microbiology.
“The technique emerging from our laboratory can be applied to the study of free-living and host-associated microbiomes, which could prove crucial in understanding more about their functional responses to stressors,” said Gordon T. Taylor, who led the research team. “We also believe this is an enabling technology to examine individuality in cell populations and could have broad applications in microbiology, cell biology and biomedicine.”
The SIP-Raman microspectroscopy method can be further combined with methods for phylogenetic identification. The single-cell variability measurements can also aid researchers in directly linking genetic identity with functional traits in single cells within mixed microbial assemblages, the authors wrote.
Photo: This montage shows a bacterial cell population by way of a Raman microspectrophotometer and a measurement assimilation of carbon-13 of the population’s proteins. Detection of the carbon-13 enrichment in individual bacterial cells helps to calculate microbial growth rates at the single-cell level. Credit: T. Zaliznyak