Photonic Data Science

Carbon catabolite repression (CCR) is a regulatory phenomenon occurring in both lower organisms like bacteria andhigher organisms like yeast which allows them to preferentially utilize a specific carbon source to achieve highest metabolicactivity and cell growth. CCR has been intensely studied in the model organisms Escherichia coli and Bacillus subtilis by followingdiauxic growth curves, assays to estimate the utilization or depletion of carbon sources, enzyme assays, Western blotting and massspectrometric analysis to monitor and quantify the involvement of specific enzymes and proteins involved in CCR. In this study, wehave visualized this process in three species of naphthalene degrading soil bacteria at a single cell level via Raman spectroscopybased stable isotope probing (Raman-SIP) using a single and double labeling approach. This is achieved using a combination of 2Hand 13C isotope labeled carbon sources like glucose, galactose, fructose and naphthalene. Time dependent metabolic flux of 13C and2H isotopes has been followed via relative quantification and 2D Raman correlation analysis. For this, the relative intensities of Raman marker bands corresponding to 2H and 13C incorporation in newly synthesized macromolecules like proteins and lipids have been utilized. The 2D correlation analysis of time dependent Raman spectra readily identified small sequential changes resultingfrom isotope incorporation. Overall, we show that Raman-SIP has the potential to be used to obtain information about regulatory processes like CCR in bacteria at a single cell level within a time span of 3 h in fast growing bacteria. We also demonstrate the potential of this approach in identifying the most efficient naphthalene degraders asserting its importance for use in bioremediation.